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[SQUEAKING]

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[RUSTLING]

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[CLICKING]

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JOHN DOLHUN: Good
morning, everyone.

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And welcome, or good afternoon.

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Welcome to The Ellen Swallow
Richards Lecture Series.

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This is our beloved
Charles River.

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This is the river you're
going to be testing.

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Once you've tested
this river, you

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can actually take this
testing and apply it

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to any body of water.

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Why should we be concerned
about this Charles River?

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Yes?

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Because we live next to it.

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Because we live--
that's a good reason.

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Because we live next to it.

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Anyone else?

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Aisha?

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AUDIENCE: To care
about your environment.

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JOHN DOLHUN: You care
about your environment.

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And speaking of caring
about your environment,

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we've got some problems
with phosphate out there.

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We've got high phosphorus
concentrations.

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And those high
phosphorus concentrations

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lead to algal blooms.

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And those algal blooms produce
toxic chemicals and odors.

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And when all this algae dies,
it heads down to the bottom

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and breaks off and it's
acted on by decomposers.

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These microbes start
to chew it apart

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and they use up the dissolved
oxygen so that we get lower--

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lower dissolved
oxygen in the water.

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And what that does is
it leads to fish kills.

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And our recreational
ability is impaired.

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So here are some examples
of what I'm talking about.

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This is Florida, 2016.

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This is Lake Okeechobee, one of
the largest fresh water lakes

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in Florida.

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This is a 30 mile
long fish kill.

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It involves some
50 species of fish.

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The cause, most
probably, an algal bloom,

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the result of leaking
septic systems,

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fertilizers from lawns
going into the water.

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This is an economic disaster.

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It's going to take decades
to recover from this.

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Is Bradenton, Florida, 2018.

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This is their harbor
filled with dead fish.

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This started from an algal bloom
that turned into a red tide.

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And the red tide
stretched about 150 miles

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off the coast of
Florida, and gradually,

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the wind and the currents
brought it into shore.

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And when that red
tide came in to shore,

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it started releasing toxins
into the air and water,

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and then the nutrients
broke off and microbes

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started digesting them
and used up the oxygen,

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and all these fish died.

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This is Australia, 2019.

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This is the Darling River,
but it also happened in

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the [INAUDIBLE] River.

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And they had a successive
run of these fish kills,

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one right after the other.

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Again, it's global
hot temperatures

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and agricultural runoff.

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This is the Charles
River, August, 2019.

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This is the largest
algal bloom, I think,

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that we've had out there.

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It actually stretched
from the BU bridge

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to the Museum of Science.

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And cyanobacteria was detected.

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This is a health problem.

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So we're going to be measuring
phosphorus in the waters

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out here.

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That's one of the things
we're going to do.

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And there are two
types of phosphorus,

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there's the inorganic,
which is simply

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salts of phosphoric
acid, and then

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if you create esters
of the inorganic form,

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you have the organic
form of phosphate.

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So let's take a
look for a moment

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at the inorganic phosphate.

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I mean, phosphorus is like,
the 11th most abundant element

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on the planet.

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And it's not found
in elemental form.

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You won't find any pure
phosphorous anywhere

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on the Earth.

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It's found in these types of
phosphates, in rocks and soils,

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and that's how it exists.

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So the main inorganic player
here is the orthophosphate.

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And that's the PO4
to the 3 minus.

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This is the most stable
form of phosphorus.

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And this is the form that's
readily available to plants

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for uptake by the plants.

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I mean, all plants and animals
need phosphorus for growth.

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It's the backbone of our
DNA and the Krebs cycle.

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Plants need it in
photosynthesis.

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They have to extract it
from their environment

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because they're not going to
make sugar unless they first

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make ATP to actually connect
those bonds in the sugars

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that they're making.

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So we've got this
orthophosphate, the main player

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here, but in the
inorganic category,

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you can actually
connect several of these

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together and form
a polyphosphate,

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such as our detergents.

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A lot of detergents
are polyphosphates.

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P3O10 to the 5 minus
would be a polyphosphate.

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The interesting thing
about the polyphosphates

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is as soon as they
hit the water,

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they hydrolyze into
the orthophosphate.

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And then we've got the
organic phosphates,

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which are esters of
the inorganic form.

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And organic phosphates are
found in all living tissues.

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So all living tissues,
both plants and animals,

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have organic phosphates.

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And waste is also another form
of the organic phosphates.

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So when something living
dies, it starts to decay.

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What happens is the
phosphates actually

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convert to the orthophosphate.

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That's what happens to them.

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So this is what we're
going to be measuring.

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And now, I'd like to talk
for a few minutes about how

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it gets into the water, where
all this stuff is coming from.

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So we're going to look at
some of the primary sources

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of the phosphorus.

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The first one is
storm water runoff.

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Can anyone give me an example
of some phosphoruses, phosphates

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that can get into the water
from storm water runoff?

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Yes, Aisha.

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AUDIENCE: I'm not sure if
there's a phosphate in dirt.

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JOHN DOLHUN: Absolutely.

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There's phosphate in the dirt.

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And that would get washed in.

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What else?

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Yes, Jimmy?

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AUDIENCE: Probably less
here, but in agriculture,

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I'm pretty sure they're
used in fertilizer.

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JOHN DOLHUN: Oh, gosh, yes.

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Fertilizers are a big
thing because of lawns.

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So we've got soil
here and fertilizers.

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Anything else?

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Jimmy?

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AUDIENCE: I guess
animal droppings?

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JOHN DOLHUN: Absolutely.

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Animal waste.

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I mean, think about where
do they put pig farms?

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They put them all
by a river, right?

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And all those geese, the guano,
droppings, everything, they're

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all out there by the river.

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And all that stuff
is being washed in.

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So animal waste is a
big, big source here.

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Anything else?

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You ever got your car
washed in a car wash?

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Do you ever sit in it
while you're going through,

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see all that soap coming down?

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Tons of soap.

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And all that soap's going
into the sewer systems,

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and when it starts to rain,
heavy rains, it bubbles over.

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So car washes would
be a big source,

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and there's your polyphosphates.

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Another one that you might
not be as familiar with

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is car exhausts.

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Car exhausts have a
catalyst tube in there.

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When that tube gets hot,
like 500, 600, 700 degrees,

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it can form cerium
phosphate, which is released

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in the exhaust effluent.

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So cerium phosphate
would be a culprit here.

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And then probably
the biggest source

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is discharge from
wastewater treatment plants.

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Did any of you ever go to tour
a wastewater treatment plant?

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Anyone?

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Oh, you did?

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Kelly, right?

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Could you tell us--
tell us about it,

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what your experience was?

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AUDIENCE: It was a school
fieldtrip a long time ago,

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I think.

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It was interesting.

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So they purified
or treat the water

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with several different methods.

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On of them was just
like, bacterial,

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and then they introduce
it [INAUDIBLE]..

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JOHN DOLHUN: Yeah, they
aerate it with bacteria,

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I think, in the
secondary treatment.

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And they do that to get
rid of organic matter

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or to digest it down to sludge.

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AUDIENCE: Yeah.

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And then there's a UV method.

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JOHN DOLHUN: Very good.

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I mean, the most modern plants
have this ultraviolet rays

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at the very end.

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You can walk along and
you can see a glass floor.

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You can see the
water going through

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with the ultraviolet
rays hitting it.

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And then, at the end,
they have a faucet

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and they offer you a drink.

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I mean, there was
no one in my group

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that availed themself to
take a sip of that water

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after going through that.

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But let's put this
in perspective.

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So wastewater treatment
plants, they're

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all built along
rivers or oceans.

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And when a heavy rain,
they start to discharge.

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They have to discharge.

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They can't take the flow.

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First thing, they
may discharge some

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of the secondary treated water.

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Sometimes, they have to
discharge the raw sewage.

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But to put it in
perspective, all of us

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produce about 2.2
grams of pee per day.

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I'm talking about
phosphorus here.

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That's about 1.8
pounds per year.

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Now, when that phosphorus hits
the sewage treatment plant,

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it's in the effluent,
it gets diluted down.

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You're talking
somewhere between 2

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and probably 20 milligrams
per liter PPM of phosphorous

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in the water.

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After the secondary
treatment, they only

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take out between 1 and
2 milligrams per liter.

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So you end up with a
large excess of phosphorus

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in the treated water.

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So when they release,
it's a ton of phosphorus

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hitting the water.

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But the good news is--

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I'm going to draw a smiley
face here, because the EPA just

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filed a regulation forcing--

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they're going to force all
these wastewater treatment

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plants to cut back, get rid of
the phosphorus in the water,

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and they're going
to have to-- they're

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going to have to
take it down to less

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than 1.0 milligrams per liter.

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So all these plants are running
around now trying to figure out

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how they're going to do that.

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This, I believe, just went
into effect this year,

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and may go-- may be
starting in January of 2020,

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but there are EPA regulations
that are just coming out.

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The other major source
is sewer overflows.

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And in New England, everyone--

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it's notorious that you have
a sump pump in your basement.

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So when your basement
floods, the pump starts up

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and it pumps everything.

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They're connected to
the sewer systems.

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So everything in
the kitchen sink

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is going into the sewer
system and it's bubbling over.

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So those are the
primary sources.

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Now, let's look at
the ecological effect

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of all this phosphorus.

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This is the Charles River,
the famous Charles River.

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This is up by Newton, Mass.

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There's a guy in a canoe trying
to pull out the vegetation

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out of the water.

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What this vegetation
does is two things.

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First, it's blocking
the sunlight

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to organisms and other plants
down below the surface that

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need that sun.

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00:16:52,920 --> 00:16:57,270
And the second thing is it's
going to die and produce

255
00:16:57,270 --> 00:17:01,560
these swamp-like
odors, and then it's

256
00:17:01,560 --> 00:17:04,800
going to get decomposed
by microorganisms that

257
00:17:04,800 --> 00:17:07,599
are going to use up the oxygen.

258
00:17:07,599 --> 00:17:11,039
This is the result. This
is blue-green algae.

259
00:17:14,440 --> 00:17:19,060
This is really-- another name
for this is cyanobacteria.

260
00:17:19,060 --> 00:17:22,839
It's the cyanobacteria that
give it that green color

261
00:17:22,839 --> 00:17:24,329
on the surface of the water.

262
00:17:27,050 --> 00:17:29,660
Here are some other forms of it.

263
00:17:29,660 --> 00:17:33,140
You can get this pea
soup kind of look,

264
00:17:33,140 --> 00:17:35,900
or you can get this
mossy look, or you

265
00:17:35,900 --> 00:17:38,240
might get a painted look.

266
00:17:38,240 --> 00:17:42,470
The bottom line is
it's all bacteria.

267
00:17:42,470 --> 00:17:45,350
It's unicellular bacteria.

268
00:17:45,350 --> 00:17:47,600
These are prokaryotic bacteria.

269
00:17:47,600 --> 00:17:51,140
They have no nucleus, but
they make their own food

270
00:17:51,140 --> 00:17:54,780
and they secrete chemicals.

271
00:17:54,780 --> 00:17:57,990
These are the same
bacteria, believe it or not,

272
00:17:57,990 --> 00:18:02,530
that gave us life 3.5
billion years ago.

273
00:18:02,530 --> 00:18:04,500
And now, they're out to get us.

274
00:18:04,500 --> 00:18:06,990
Isn't that amazing?

275
00:18:06,990 --> 00:18:10,300
Every time I look at
this, I can't believe it.

276
00:18:10,300 --> 00:18:12,120
I mean, when we had
no oxygen, these

277
00:18:12,120 --> 00:18:14,850
were the guys that were
giving our oxygen atmosphere,

278
00:18:14,850 --> 00:18:17,820
and now, look what
they're doing.

279
00:18:17,820 --> 00:18:22,540
Now, if these are out
there in the water,

280
00:18:22,540 --> 00:18:24,210
you don't want to
go in the water.

281
00:18:24,210 --> 00:18:28,950
If you do, you are dead
meat, and I'll tell you why.

282
00:18:28,950 --> 00:18:30,930
You can have all
kinds of symptoms,

283
00:18:30,930 --> 00:18:33,900
you can get covered
with a rash, you

284
00:18:33,900 --> 00:18:38,430
can have diarrhea, flu-like
symptoms, eye and ear problems,

285
00:18:38,430 --> 00:18:41,070
respiratory problems.

286
00:18:41,070 --> 00:18:44,610
I gave you an
article in the news.

287
00:18:44,610 --> 00:18:46,770
This is The New York Times.

288
00:18:46,770 --> 00:18:51,180
Central Park in New
York, all of their ponds,

289
00:18:51,180 --> 00:18:53,730
infected with blue-green algae.

290
00:18:57,400 --> 00:18:58,940
Here's a good example.

291
00:18:58,940 --> 00:19:02,860
This is today, "Ohio strikes
a Blow in Algae Fight."

292
00:19:02,860 --> 00:19:05,590
This is The Wall Street
Journal this morning.

293
00:19:05,590 --> 00:19:08,020
This article just came out.

294
00:19:08,020 --> 00:19:12,680
Interestingly, Ohio had this
algae problem 10 years ago,

295
00:19:12,680 --> 00:19:14,650
and they took around
one of their lakes

296
00:19:14,650 --> 00:19:19,990
and they built up
these wetland areas

297
00:19:19,990 --> 00:19:22,840
to prevent the runoff
from reaching--

298
00:19:22,840 --> 00:19:25,120
the agricultural runoff
from reaching the lake,

299
00:19:25,120 --> 00:19:27,460
and it's actually working.

300
00:19:27,460 --> 00:19:30,490
So there are ideas
out there that you

301
00:19:30,490 --> 00:19:32,605
can come up with an idea
and solve a problem.

302
00:19:38,680 --> 00:19:41,850
So some of these cyanobacteria,
some of the fresh water

303
00:19:41,850 --> 00:19:46,050
bacteria produce
very toxic chemicals.

304
00:19:46,050 --> 00:19:50,070
One form of these
are the microcystins.

305
00:19:50,070 --> 00:19:53,910
There are something like 50
different micocystins that

306
00:19:53,910 --> 00:19:56,220
have been identified to date.

307
00:19:56,220 --> 00:19:59,320
It's a cyclic peptide here.

308
00:19:59,320 --> 00:20:01,950
And this is a hepatotoxin.

309
00:20:01,950 --> 00:20:06,310
So once this gets through
your skin into your body,

310
00:20:06,310 --> 00:20:09,660
your liver is going
to get attacked,

311
00:20:09,660 --> 00:20:11,850
and you're pretty much gone.

312
00:20:11,850 --> 00:20:14,080
There's not much
you can do about it.

313
00:20:14,080 --> 00:20:16,020
The article mentions the dogs--

314
00:20:16,020 --> 00:20:19,480
one woman had three
dogs in North Carolina.

315
00:20:19,480 --> 00:20:21,840
She let them go for
a swim in a pond.

316
00:20:21,840 --> 00:20:25,860
All three dogs died
within a few hours.

317
00:20:25,860 --> 00:20:28,670
So this is really nasty stuff.

318
00:20:28,670 --> 00:20:33,020
And I challenge you to
think about coming up

319
00:20:33,020 --> 00:20:34,400
with an antidote for this.

320
00:20:36,960 --> 00:20:39,090
There's your startup
company right here.

321
00:20:39,090 --> 00:20:40,290
I'm giving it to you.

322
00:20:43,890 --> 00:20:47,220
When this stuff is active, you
go out to the Charles River,

323
00:20:47,220 --> 00:20:50,700
you'll see these signs posted
warning people and pets

324
00:20:50,700 --> 00:20:52,460
to stay out of the water.

325
00:20:55,950 --> 00:20:57,310
Here's another example.

326
00:20:57,310 --> 00:21:00,720
This is the summer of 2014.

327
00:21:00,720 --> 00:21:04,440
This is a satellite
picture of Lake Erie, one

328
00:21:04,440 --> 00:21:07,680
of the five Great
Lakes in this country.

329
00:21:07,680 --> 00:21:13,170
And the lake actually borders
Canada on one side, separates

330
00:21:13,170 --> 00:21:16,320
Canada from the US near
Ontario, and then there

331
00:21:16,320 --> 00:21:20,250
are several states
that border the lake.

332
00:21:20,250 --> 00:21:25,380
Out here to the west is
Toledo, Ohio, and Toledo,

333
00:21:25,380 --> 00:21:28,260
fourth largest city in
Ohio, has a population

334
00:21:28,260 --> 00:21:30,570
of about a half million.

335
00:21:30,570 --> 00:21:35,130
This was their
tap water in 2014.

336
00:21:35,130 --> 00:21:40,590
And I had a 5.310 student
in class four years ago who

337
00:21:40,590 --> 00:21:43,200
remembers this.

338
00:21:43,200 --> 00:21:46,380
I mean, this is
serious business.

339
00:21:46,380 --> 00:21:48,580
And it's happening all
over, all over the world.

340
00:21:51,230 --> 00:21:52,280
Here's another picture.

341
00:21:52,280 --> 00:21:58,710
This is the largest landlocked
body of water on the Earth.

342
00:21:58,710 --> 00:22:01,290
Anybody from Europe
here recognize this?

343
00:22:07,440 --> 00:22:07,940
What?

344
00:22:07,940 --> 00:22:09,350
Who said that?

345
00:22:09,350 --> 00:22:12,710
Yes, Sean, exactly correct,
that's the Caspian Sea.

346
00:22:12,710 --> 00:22:14,750
It's bordered by five countries.

347
00:22:14,750 --> 00:22:19,670
But look at the massive,
massive algal growth

348
00:22:19,670 --> 00:22:21,410
from this satellite picture.

349
00:22:21,410 --> 00:22:26,030
Here's the Volga River, Europe's
longest river, pouring into it.

350
00:22:26,030 --> 00:22:29,250
It's a 2,000 mile long river.

351
00:22:29,250 --> 00:22:33,870
Here's a new word for
you, eutrophication.

352
00:22:33,870 --> 00:22:37,220
It's from the Greek
meaning well nourished.

353
00:22:40,580 --> 00:22:45,410
So how much phosphorus
is acceptable?

354
00:22:45,410 --> 00:22:48,530
The EPA came out in 2000--

355
00:22:48,530 --> 00:22:50,930
that was almost 20 years ago--

356
00:22:50,930 --> 00:22:55,760
and said 0.0238
milligrams per liter.

357
00:22:55,760 --> 00:23:00,230
Well, we know today that
if you have anything

358
00:23:00,230 --> 00:23:09,530
greater than or equal to
0.016 milligrams per liter,

359
00:23:09,530 --> 00:23:15,260
you're going to have
really a large algal growth

360
00:23:15,260 --> 00:23:18,890
proliferating in your water.

361
00:23:18,890 --> 00:23:23,590
Now, these concentrations
of phosphorus, they're low.

362
00:23:23,590 --> 00:23:26,890
And it's going to be
challenging to measure those.

363
00:23:26,890 --> 00:23:29,150
This is what we're going to do.

364
00:23:29,150 --> 00:23:31,390
The other thing that
makes it challenging

365
00:23:31,390 --> 00:23:38,690
is phosphates are colorless.

366
00:23:38,690 --> 00:23:41,630
So how are we going to
use UV vis to measure

367
00:23:41,630 --> 00:23:43,040
these concentrations?

368
00:23:46,700 --> 00:23:47,890
Anybody have an idea?

369
00:23:57,310 --> 00:23:58,480
Yes?

370
00:23:58,480 --> 00:24:01,240
Maybe we can react
them with something

371
00:24:01,240 --> 00:24:03,090
that will make them colorful?

372
00:24:03,090 --> 00:24:05,340
Maybe we can react
them with something

373
00:24:05,340 --> 00:24:06,570
that can make them colorful.

374
00:24:06,570 --> 00:24:08,040
Very good.

375
00:24:08,040 --> 00:24:09,000
Very good.

376
00:24:09,000 --> 00:24:11,220
Yeah, I like that.

377
00:24:11,220 --> 00:24:12,650
Keisha, right?

378
00:24:12,650 --> 00:24:14,865
AUDIENCE: Gizelle.

379
00:24:14,865 --> 00:24:15,740
JOHN DOLHUN: Gizelle.

380
00:24:15,740 --> 00:24:17,270
I'm sorry, Gizelle.

381
00:24:17,270 --> 00:24:18,810
Where's Keisha?

382
00:24:18,810 --> 00:24:19,670
There she is.

383
00:24:19,670 --> 00:24:20,960
OK.

384
00:24:20,960 --> 00:24:23,540
All right, so react
them with something

385
00:24:23,540 --> 00:24:26,180
that makes it colorful.

386
00:24:26,180 --> 00:24:30,410
So here comes chemistry
to the rescue, right?

387
00:24:30,410 --> 00:24:34,280
So phosphates are very reactive.

388
00:24:34,280 --> 00:24:39,560
So we can actually take river
water and this method here,

389
00:24:39,560 --> 00:24:42,590
this is the ammonium
metavanadate method.

390
00:24:42,590 --> 00:24:48,320
When I tried to develop this
Charles River water testing,

391
00:24:48,320 --> 00:24:50,660
I started with this
method because it

392
00:24:50,660 --> 00:24:54,440
was written up as the
method to detect phosphorus

393
00:24:54,440 --> 00:24:56,000
in river water.

394
00:24:56,000 --> 00:24:57,860
So you would take
the river water,

395
00:24:57,860 --> 00:25:01,850
mix it with molybdate,
ammonium metavanadate,

396
00:25:01,850 --> 00:25:07,340
and you create this color
heteropoly molybdic acid

397
00:25:07,340 --> 00:25:10,250
that has a yellow color
and it absorbs light

398
00:25:10,250 --> 00:25:14,240
at 400 nanometers.

399
00:25:14,240 --> 00:25:19,160
What I found is that this
method was not sensitive enough

400
00:25:19,160 --> 00:25:21,980
to actually measure
the phosphorus

401
00:25:21,980 --> 00:25:25,130
levels in the Charles River.

402
00:25:25,130 --> 00:25:28,700
It's a great method for
measuring phosphorus in sewage,

403
00:25:28,700 --> 00:25:30,560
but not the rivers.

404
00:25:30,560 --> 00:25:32,690
So I looked around
and I found what's

405
00:25:32,690 --> 00:25:38,120
called the ascorbic acid method,
an EPA-approved method where

406
00:25:38,120 --> 00:25:43,340
you actually took
river water, mixed it

407
00:25:43,340 --> 00:25:47,210
with molybdate,
sulfuric acid, and you

408
00:25:47,210 --> 00:25:53,090
create this heteropoly molybdic
acid, which is colorless.

409
00:25:53,090 --> 00:25:59,090
But the good thing is this
heteropoly molybdate anion

410
00:25:59,090 --> 00:26:03,260
can accept electrons
and be reduced down

411
00:26:03,260 --> 00:26:07,620
and ascorbic acid can
cause that reduction.

412
00:26:07,620 --> 00:26:11,600
And you end up getting this
molybdenum blue complex,

413
00:26:11,600 --> 00:26:14,810
a mixed valence complex
that absorbs light

414
00:26:14,810 --> 00:26:19,630
at 880 nanometers.

415
00:26:19,630 --> 00:26:22,450
So this is great because
the concentration

416
00:26:22,450 --> 00:26:25,450
of the phosphorus
in the complexes

417
00:26:25,450 --> 00:26:27,340
is proportional
to the absorbance

418
00:26:27,340 --> 00:26:30,620
of the light in these things.

419
00:26:30,620 --> 00:26:34,060
So this is what you're
actually making.

420
00:26:34,060 --> 00:26:35,020
It's beautiful.

421
00:26:35,020 --> 00:26:36,970
This is a Keggin structure.

422
00:26:36,970 --> 00:26:41,770
It captures the phosphorus in
the center, surrounded by 12

423
00:26:41,770 --> 00:26:45,790
molybdenums and 40 oxygens.

424
00:26:45,790 --> 00:26:49,360
I want you to take a
moment and look at this.

425
00:26:49,360 --> 00:26:52,120
And I'd like you all to
close your eyes for a moment

426
00:26:52,120 --> 00:26:54,490
and think about this image.

427
00:26:54,490 --> 00:26:55,390
Close your eyes.

428
00:27:02,260 --> 00:27:05,770
OK, open your eyes, please.

429
00:27:05,770 --> 00:27:09,010
I want you to carry
this image with you

430
00:27:09,010 --> 00:27:13,690
into the lab when you
do this experiment.

431
00:27:13,690 --> 00:27:17,280
You're actually going to be
making this in your beakers

432
00:27:17,280 --> 00:27:21,330
when you add the color
developer to your water samples.

433
00:27:21,330 --> 00:27:26,310
You're creating this in about
15 minutes in your beaker.

434
00:27:26,310 --> 00:27:28,695
This is inorganic
chemistry at its best.

435
00:27:31,490 --> 00:27:36,410
Now, I want to spend the next
several slides showing you

436
00:27:36,410 --> 00:27:39,080
how we're going to
actually measure

437
00:27:39,080 --> 00:27:43,080
the concentrations of this.

438
00:27:43,080 --> 00:27:47,240
So we're going to be shining
electromagnetic energy

439
00:27:47,240 --> 00:27:49,710
on a sample.

440
00:27:49,710 --> 00:27:52,640
And if you look at
the visible light

441
00:27:52,640 --> 00:27:57,020
here that I broke out of this
electromagnetic spectrum,

442
00:27:57,020 --> 00:28:01,100
on the red end of
this, we're going

443
00:28:01,100 --> 00:28:04,760
to be looking at our
samples on that far red end

444
00:28:04,760 --> 00:28:07,010
in the near IR.

445
00:28:07,010 --> 00:28:08,720
So that's where
you're going to be--

446
00:28:08,720 --> 00:28:10,670
where you're going to
be taking your readings.

447
00:28:10,670 --> 00:28:15,585
Now, what can happen when you
shine radiation on your sample?

448
00:28:15,585 --> 00:28:16,085
Anyone?

449
00:28:19,590 --> 00:28:20,655
Yes, Kim.

450
00:28:20,655 --> 00:28:24,904
AUDIENCE: Photobleaching

451
00:28:24,904 --> 00:28:25,696
JOHN DOLHUN: Sorry?

452
00:28:25,696 --> 00:28:28,080
AUDIENCE: Some of your sample
could get photobleached.

453
00:28:28,080 --> 00:28:30,840
JOHN DOLHUN: Some of your sample
could get photobleached, yeah.

454
00:28:30,840 --> 00:28:33,020
That's a possibility.

455
00:28:33,020 --> 00:28:35,910
What else?

456
00:28:35,910 --> 00:28:36,410
Yes?

457
00:28:36,410 --> 00:28:39,679
AUDIENCE: [INAUDIBLE]

458
00:28:43,420 --> 00:28:44,480
JOHN DOLHUN: Exactly.

459
00:28:44,480 --> 00:28:46,600
I mean, electrons
could get chewed up

460
00:28:46,600 --> 00:28:48,490
to a higher energy levels.

461
00:28:48,490 --> 00:28:51,190
Little nuclei could see
that happen and get nervous

462
00:28:51,190 --> 00:28:53,320
and start to
rearrange themselves.

463
00:28:53,320 --> 00:28:56,980
And the molecule, as Kelly said,
could burst into vibration.

464
00:28:56,980 --> 00:29:06,030
And your UV is
actually monitoring

465
00:29:06,030 --> 00:29:08,850
all of those electronic
transmissions

466
00:29:08,850 --> 00:29:12,570
that we can't see with our eye.

467
00:29:12,570 --> 00:29:17,980
And what the UV does is it draws
you a smooth curve through all

468
00:29:17,980 --> 00:29:21,400
of those electronic transitions
and you end up somewhere

469
00:29:21,400 --> 00:29:24,550
with your lambda max.

470
00:29:24,550 --> 00:29:28,390
What UV vis is,
a good definition

471
00:29:28,390 --> 00:29:31,810
is it's just the interaction
of light with matter

472
00:29:31,810 --> 00:29:33,991
as a function of wavelength.

473
00:29:37,760 --> 00:29:39,820
So here's your UV cuvette.

474
00:29:39,820 --> 00:29:43,040
Here's the radiation
hitting that cuvette.

475
00:29:43,040 --> 00:29:45,640
What happens?

476
00:29:45,640 --> 00:29:47,583
What do you see up
there happening?

477
00:29:53,270 --> 00:29:54,070
Yes, Ryan?

478
00:29:58,855 --> 00:30:00,070
Yeah, the lights focused.

479
00:30:00,070 --> 00:30:01,945
And what's happening
to the sample?

480
00:30:11,080 --> 00:30:13,300
I'm sure it's heating up, yeah.

481
00:30:13,300 --> 00:30:14,570
Yes, Autumn?

482
00:30:14,570 --> 00:30:17,300
AUDIENCE: It absorbs sunlight
and transmits sunlight and also

483
00:30:17,300 --> 00:30:17,800
re-emits.

484
00:30:20,190 --> 00:30:21,190
JOHN DOLHUN: Yeah, good.

485
00:30:21,190 --> 00:30:22,920
So some of the
light's going through

486
00:30:22,920 --> 00:30:24,930
and some's getting absorbed.

487
00:30:24,930 --> 00:30:27,790
So let's look at
that for a minute.

488
00:30:27,790 --> 00:30:31,920
So we've got absorbance
minus the log

489
00:30:31,920 --> 00:30:36,180
of the transmitted light,
which is i over i0.

490
00:30:38,895 --> 00:30:45,660
Now, absorbance
is-- we're actually

491
00:30:45,660 --> 00:30:47,070
monitoring the absorbance.

492
00:30:47,070 --> 00:30:49,440
We're not monitoring
the transmittance

493
00:30:49,440 --> 00:30:51,840
because absorbance
is actually directly

494
00:30:51,840 --> 00:30:57,220
proportional to
concentration by Beer's law.

495
00:30:57,220 --> 00:31:00,600
So we have this relationship.

496
00:31:00,600 --> 00:31:04,260
And E, the extinction
coefficient,

497
00:31:04,260 --> 00:31:07,440
is the molar
absorptivity constant,

498
00:31:07,440 --> 00:31:12,840
is simply the amount of
light absorbed per unit

499
00:31:12,840 --> 00:31:17,140
concentration of your sample.

500
00:31:17,140 --> 00:31:18,840
Let me just rewrite this.

501
00:31:18,840 --> 00:31:20,500
Let me get rid of the logarithm.

502
00:31:20,500 --> 00:31:22,060
I want to show you
something here.

503
00:31:22,060 --> 00:31:26,040
So I'm going to rewrite this.

504
00:31:35,140 --> 00:31:41,470
Let's actually
graph the intensity

505
00:31:41,470 --> 00:31:45,180
of the incoming radiation here.

506
00:31:45,180 --> 00:31:56,090
We're going to graph that as
a function of concentration.

507
00:31:56,090 --> 00:32:02,740
If you do that, you're going
to see from that equation

508
00:32:02,740 --> 00:32:06,820
that the transmitted light
decreases exponentially

509
00:32:06,820 --> 00:32:09,940
as the concentration increases.

510
00:32:09,940 --> 00:32:14,110
I want you to keep that
in the back of your mind.

511
00:32:14,110 --> 00:32:16,450
This equation fascinated me.

512
00:32:16,450 --> 00:32:19,480
I like Beer's law.

513
00:32:19,480 --> 00:32:22,030
What this tells you, this
extinction coefficient

514
00:32:22,030 --> 00:32:25,610
tells you, that it
has to be a constant.

515
00:32:25,610 --> 00:32:27,970
So if you cut your
concentration in half,

516
00:32:27,970 --> 00:32:30,710
absorption should
be cut in half.

517
00:32:30,710 --> 00:32:32,390
So I wanted to prove this.

518
00:32:32,390 --> 00:32:35,590
So I went out and I
made this compound,

519
00:32:35,590 --> 00:32:38,230
hexacyanoferrate(III).

520
00:32:38,230 --> 00:32:41,830
And I made up five
solutions of this,

521
00:32:41,830 --> 00:32:45,440
and then I measured the
absorbance of each solution.

522
00:32:45,440 --> 00:32:49,120
It absorbed light
at 420 nanometers.

523
00:32:49,120 --> 00:32:53,505
And if you look here, 10
times e to the minus 4,

524
00:32:53,505 --> 00:32:58,600
if I cut that in half to 5
times e to the minus 4, indeed,

525
00:32:58,600 --> 00:33:02,900
the absorption gets cut
in half as it should.

526
00:33:02,900 --> 00:33:07,690
So I graph this, got
a nice, straight line.

527
00:33:07,690 --> 00:33:10,840
The change in absorption over
the change in concentration

528
00:33:10,840 --> 00:33:11,980
is my slope.

529
00:33:11,980 --> 00:33:17,770
And it's 1,056.7 so that's
my extinction coefficient.

530
00:33:17,770 --> 00:33:21,610
And this worked really well.

531
00:33:21,610 --> 00:33:24,670
But I want to caution you--

532
00:33:24,670 --> 00:33:30,640
if you try this, and
you're graphing absorption

533
00:33:30,640 --> 00:33:34,510
versus concentration, and
you're doing Beer's law,

534
00:33:34,510 --> 00:33:36,820
you've got this
nice, straight line,

535
00:33:36,820 --> 00:33:40,180
you might end up with
something like this,

536
00:33:40,180 --> 00:33:43,600
where Beer's law falls apart.

537
00:33:43,600 --> 00:33:47,690
And it all comes
back to this here--

538
00:33:47,690 --> 00:33:49,790
the intensity of the
transmitted light

539
00:33:49,790 --> 00:33:53,190
decreases exponentially
with concentration.

540
00:33:53,190 --> 00:33:56,930
So eventually, if the
concentration is too high

541
00:33:56,930 --> 00:34:01,400
your sample becomes
saturated, and you're not

542
00:34:01,400 --> 00:34:04,310
going to be-- this
Beer's law falls apart.

543
00:34:04,310 --> 00:34:06,530
I just want you to
be aware of that.

544
00:34:06,530 --> 00:34:10,310
What I did is I made up all of
my concentrations are very low.

545
00:34:10,310 --> 00:34:13,920
Beer's law worked fine.

546
00:34:13,920 --> 00:34:21,350
So now we're going to get
to some serious business.

547
00:34:21,350 --> 00:34:25,230
This is what you have to do
for this lab, for it to work.

548
00:34:25,230 --> 00:34:27,110
Otherwise, you will be a goner--

549
00:34:27,110 --> 00:34:28,489
gonzo.

550
00:34:28,489 --> 00:34:31,719
You've got to clean
this glassware.

551
00:34:31,719 --> 00:34:34,880
This is a list of the glassware
that you'll need to clean.

552
00:34:34,880 --> 00:34:38,630
And you've got to do it with
10% hydrochloric acid, triple

553
00:34:38,630 --> 00:34:41,199
rinsed with Milli-Q Water.

554
00:34:41,199 --> 00:34:43,150
Why do you think
you need to do that?

555
00:34:47,860 --> 00:34:48,949
Yes.

556
00:34:48,949 --> 00:34:51,580
AUDIENCE: Any contamination
might change the products

557
00:34:51,580 --> 00:34:55,150
concentration.

558
00:34:55,150 --> 00:34:56,860
JOHN DOLHUN: Any
contamination is going

559
00:34:56,860 --> 00:34:59,590
to just destroy the experiment.

560
00:34:59,590 --> 00:35:01,740
It's kind of like
the Nano Building.

561
00:35:01,740 --> 00:35:05,260
You've seen them in there
with their bunny suits on.

562
00:35:05,260 --> 00:35:10,060
One speck of dust, even
a dander from your hair,

563
00:35:10,060 --> 00:35:13,510
is like a wrecking
ball to the experiment.

564
00:35:13,510 --> 00:35:18,760
Well, one speck of
phosphate from any detergent

565
00:35:18,760 --> 00:35:21,920
is going to wreck
this experiment.

566
00:35:21,920 --> 00:35:24,340
So you've got to
judiciously sit down.

567
00:35:24,340 --> 00:35:27,500
There'll be two of you-- you'll
be partnered up for this.

568
00:35:27,500 --> 00:35:29,650
So you clean this up.

569
00:35:29,650 --> 00:35:33,310
And you'll do this on day two
after the dissolved oxygen

570
00:35:33,310 --> 00:35:34,455
testing.

571
00:35:34,455 --> 00:35:35,830
This is what you're
going to need

572
00:35:35,830 --> 00:35:38,860
for day three for the
phosphate testing.

573
00:35:38,860 --> 00:35:42,070
So you can leave this
glassware in the top drawer

574
00:35:42,070 --> 00:35:43,570
above your locker.

575
00:35:43,570 --> 00:35:45,070
It's not locked.

576
00:35:45,070 --> 00:35:47,020
And it'll be nice
and ready for when

577
00:35:47,020 --> 00:35:50,570
you come in to do the testing.

578
00:35:50,570 --> 00:35:55,490
So this is what you
have to do in this lab.

579
00:35:55,490 --> 00:35:58,780
First of all, we need to
make up a set of standards

580
00:35:58,780 --> 00:36:00,670
that we can
interpolate our river

581
00:36:00,670 --> 00:36:04,960
samples against to find the
concentrations of the phosphate

582
00:36:04,960 --> 00:36:06,260
and phosphorus.

583
00:36:06,260 --> 00:36:08,710
So you're going to make
seven standards up.

584
00:36:08,710 --> 00:36:13,240
And you're going to be
using a stock solution.

585
00:36:16,580 --> 00:36:19,820
And the formula to use
in all these tables

586
00:36:19,820 --> 00:36:23,900
is you're going to use
this M1V1 equals M2V2.

587
00:36:27,810 --> 00:36:37,260
So if you have a 10 to the
minus 1/3 molar stock solution,

588
00:36:37,260 --> 00:36:45,810
and you're taking 1 milliliter
of it out, out of the bottle,

589
00:36:45,810 --> 00:36:48,255
how much molarity
do you want to make

590
00:36:48,255 --> 00:36:53,850
to make up 100 mil solution?

591
00:36:53,850 --> 00:36:56,130
You'll be diluting
this 1 mil to 100,

592
00:36:56,130 --> 00:36:59,400
and you'll see that your
x is 10 to the minus 5.

593
00:36:59,400 --> 00:37:01,470
That's your stock
solution of phosphate

594
00:37:01,470 --> 00:37:03,140
that you're going to create.

595
00:37:06,540 --> 00:37:09,300
So you just use that
formula for all these.

596
00:37:09,300 --> 00:37:11,640
You're taking this
much out of your 10

597
00:37:11,640 --> 00:37:14,220
to the minus 5 molar
stock solution,

598
00:37:14,220 --> 00:37:16,800
and you're diluting
it up to 10 mils.

599
00:37:16,800 --> 00:37:19,230
What's my concentration?

600
00:37:19,230 --> 00:37:20,730
Perfect.

601
00:37:20,730 --> 00:37:22,590
What you'll do is you'll
come into the lab,

602
00:37:22,590 --> 00:37:25,170
and the TAs will go
through this with you.

603
00:37:25,170 --> 00:37:27,990
You'll make up your
stock solutions.

604
00:37:27,990 --> 00:37:31,410
And then you'll go to the
river to get your water.

605
00:37:31,410 --> 00:37:36,690
And when you bring the
water back to the lab,

606
00:37:36,690 --> 00:37:38,260
there'll be two of you.

607
00:37:38,260 --> 00:37:41,070
So one of you will
go over to the hoods

608
00:37:41,070 --> 00:37:43,320
and get the color developer.

609
00:37:43,320 --> 00:37:47,190
And these are the four
chemicals that we talked about

610
00:37:47,190 --> 00:37:48,930
in the color developer--

611
00:37:48,930 --> 00:37:54,150
the ammonium molybdate,
sulfuric acid, ascorbic acid,

612
00:37:54,150 --> 00:37:56,910
potassium antimonyl-tartrate.

613
00:37:56,910 --> 00:38:01,080
Potassium antimonyl-tartrate
is there to actually speed up

614
00:38:01,080 --> 00:38:05,190
the reduction that's going
on with ascorbic acid.

615
00:38:05,190 --> 00:38:07,110
That's important.

616
00:38:07,110 --> 00:38:11,460
If I didn't mention that before,
that's the purpose of that.

617
00:38:11,460 --> 00:38:13,830
The ammonium molybdate,
sulfuric acid,

618
00:38:13,830 --> 00:38:16,380
you're creating that
Keggin structure,

619
00:38:16,380 --> 00:38:20,460
that heteropoly,
colorless, molybdic acid.

620
00:38:20,460 --> 00:38:23,520
You also have to take this
color developer in the order

621
00:38:23,520 --> 00:38:25,050
that it's written here.

622
00:38:25,050 --> 00:38:28,230
It'll be set up in
burettes in the hood.

623
00:38:28,230 --> 00:38:31,620
If you, for example,
take it in a wrong order,

624
00:38:31,620 --> 00:38:34,170
you could have a side
reaction, and not

625
00:38:34,170 --> 00:38:39,280
get the color developer that
you want to put in your sample.

626
00:38:39,280 --> 00:38:40,540
So it's important.

627
00:38:40,540 --> 00:38:43,860
So one of you will go to the
hood, get the color developer.

628
00:38:43,860 --> 00:38:47,910
The other one will go to the
river water you brought back,

629
00:38:47,910 --> 00:38:51,210
use a clean pipette,
10 mL pipette,

630
00:38:51,210 --> 00:38:55,095
and pipette five beakers
with river water, five

631
00:38:55,095 --> 00:38:56,790
10-mL beakers.

632
00:38:56,790 --> 00:39:02,790
So you'll end up with 12-- seven
standards and five samples.

633
00:39:02,790 --> 00:39:04,920
And then you add
the color developer,

634
00:39:04,920 --> 00:39:10,240
and you wait 20 minutes,
and you're ready to go.

635
00:39:10,240 --> 00:39:15,450
Just a couple other precautions
that you should take--

636
00:39:15,450 --> 00:39:18,020
we're going to be
using 4-mL cuvettes.

637
00:39:18,020 --> 00:39:19,290
These are big inside.

638
00:39:19,290 --> 00:39:22,410
Don't use the 1 and
1/2 mL cuvettes.

639
00:39:22,410 --> 00:39:26,940
The other thing is all these
cuvettes have a fill line.

640
00:39:26,940 --> 00:39:30,000
It becomes frosted at one point.

641
00:39:30,000 --> 00:39:33,900
And you want to stop pouring
when you get to that line.

642
00:39:33,900 --> 00:39:35,490
You're going to
take your beakers,

643
00:39:35,490 --> 00:39:37,620
and you're going to
swirl them gently.

644
00:39:37,620 --> 00:39:39,720
And you're going to
pour them by hand

645
00:39:39,720 --> 00:39:41,760
until you reach the fill line.

646
00:39:41,760 --> 00:39:43,410
Don't go beyond that.

647
00:39:43,410 --> 00:39:48,090
Also, all of these UV cuvettes
have an arrow on one side.

648
00:39:48,090 --> 00:39:50,220
You want to be sure
that the arrow is

649
00:39:50,220 --> 00:39:53,580
in the light beam when you
put these cuvettes in the UV

650
00:39:53,580 --> 00:39:54,960
spectrometer.

651
00:39:54,960 --> 00:39:56,960
A lot of people
have made mistakes,

652
00:39:56,960 --> 00:39:58,710
put them in the wrong
way, and then you're

653
00:39:58,710 --> 00:40:01,080
not going to get
very good readings.

654
00:40:01,080 --> 00:40:02,880
So the arrow's clear to see.

655
00:40:02,880 --> 00:40:05,790
What I usually do is
arrange all my cuvettes

656
00:40:05,790 --> 00:40:07,770
in a box ahead of time.

657
00:40:07,770 --> 00:40:10,590
And then I pour my samples
and put them in the box,

658
00:40:10,590 --> 00:40:12,970
and I know the arrow's
in the right place.

659
00:40:12,970 --> 00:40:15,780
And when I go to the UV, I just
lift them up and put them in.

660
00:40:18,300 --> 00:40:23,160
Also, keep in mind what
Dr. Sarah Hewett told you

661
00:40:23,160 --> 00:40:27,120
the other day that there's two
kinds of pipettes in the lab.

662
00:40:27,120 --> 00:40:29,910
This one is a blowout pipette.

663
00:40:29,910 --> 00:40:33,480
You've got to blow it all
out to get your 10 mLs.

664
00:40:33,480 --> 00:40:36,660
This one is a to
deliver pipette.

665
00:40:36,660 --> 00:40:38,430
You only go up to
that last line.

666
00:40:38,430 --> 00:40:42,750
You don't blow the tip in,
otherwise you put too much--

667
00:40:42,750 --> 00:40:44,560
going to wreck your experiment.

668
00:40:44,560 --> 00:40:46,860
So make sure you look at
the pipettes carefully.

669
00:40:49,880 --> 00:40:53,910
So you're going to get your
graph here, a nice graph.

670
00:40:53,910 --> 00:40:55,610
And what you're
going to do is you're

671
00:40:55,610 --> 00:40:58,250
going to interpolate
now your river

672
00:40:58,250 --> 00:41:01,760
absorbances against the
curve so you can read off

673
00:41:01,760 --> 00:41:03,050
the concentrations.

674
00:41:12,820 --> 00:41:19,330
So the concentrations in
that graph are in micromolar.

675
00:41:19,330 --> 00:41:21,760
So you're going to want
to take those and convert

676
00:41:21,760 --> 00:41:24,440
them to milligrams per liter.

677
00:41:24,440 --> 00:41:26,230
So you want to
convert this first

678
00:41:26,230 --> 00:41:31,780
to a molarity, moles per liter.

679
00:41:34,930 --> 00:41:44,740
Then you take that, and you want
to go down to grams per liter,

680
00:41:44,740 --> 00:41:47,440
and then finally
milligrams per liter.

681
00:41:52,110 --> 00:41:54,550
So you're going to be
calculating two things.

682
00:41:54,550 --> 00:42:02,110
You want to calculate the
phosphate concentration in ppm,

683
00:42:02,110 --> 00:42:04,510
which is milligrams per
liter, and the phosphorus

684
00:42:04,510 --> 00:42:06,050
concentration.

685
00:42:06,050 --> 00:42:10,630
So you'll take your mass
from the curve in milligrams

686
00:42:10,630 --> 00:42:16,090
per liter, and take it times
the ratio for phosphate of PO4

687
00:42:16,090 --> 00:42:18,040
over KH2PO4.

688
00:42:18,040 --> 00:42:20,770
And that ratio is 0.70.

689
00:42:20,770 --> 00:42:23,680
And then for phosphorus,
do the same thing.

690
00:42:23,680 --> 00:42:26,410
The ratio there is 0.23.

691
00:42:26,410 --> 00:42:29,380
And this is the most
important part of this lab--

692
00:42:29,380 --> 00:42:32,290
this is the whole
thing, calculating

693
00:42:32,290 --> 00:42:35,140
these concentrations in the end.

694
00:42:35,140 --> 00:42:39,650
So it's important to
know how to do that.

695
00:42:39,650 --> 00:42:42,070
So once you get
your concentrations,

696
00:42:42,070 --> 00:42:45,550
you've got a series of
things to go through here

697
00:42:45,550 --> 00:42:48,190
for your data analysis.

698
00:42:48,190 --> 00:42:52,210
There's no error propagation
on this part of the lab, which

699
00:42:52,210 --> 00:42:54,680
is good for you.

700
00:42:54,680 --> 00:42:57,370
You will have to use
the LINEST equation

701
00:42:57,370 --> 00:43:01,570
that Sarah talked about,
which is pretty easy to use.

702
00:43:01,570 --> 00:43:04,750
And that'll help you calculate
the errors of your slope

703
00:43:04,750 --> 00:43:07,070
intercept and y values.

704
00:43:07,070 --> 00:43:10,120
And then you find your
average and standard deviation

705
00:43:10,120 --> 00:43:14,080
of the five measurements,
calculate the 95% confidence

706
00:43:14,080 --> 00:43:15,520
interval.

707
00:43:15,520 --> 00:43:18,460
Most importantly, report
the final concentration

708
00:43:18,460 --> 00:43:20,980
of P and PO4.

709
00:43:20,980 --> 00:43:26,260
Make sure all these results
show up in your abstract.

710
00:43:26,260 --> 00:43:28,570
First thing I do when
I get lab reports is I

711
00:43:28,570 --> 00:43:29,920
look at the abstract.

712
00:43:29,920 --> 00:43:35,890
I want to see a line
that shows my results.

713
00:43:35,890 --> 00:43:39,670
And they also should
appear in your conclusion,

714
00:43:39,670 --> 00:43:43,970
and then you can discuss them
in your discussion of your lab

715
00:43:43,970 --> 00:43:44,470
report.

716
00:43:47,700 --> 00:43:51,390
So any questions about this?

717
00:43:51,390 --> 00:43:55,320
I know you're going to have
a busy weekend because you're

718
00:43:55,320 --> 00:43:58,980
going to be working on your
ferrocene lab, your first lab

719
00:43:58,980 --> 00:44:00,360
report.

720
00:44:00,360 --> 00:44:02,340
And I want to tell
you that please,

721
00:44:02,340 --> 00:44:05,370
feel free to reach
out to me or Sarah

722
00:44:05,370 --> 00:44:07,680
if you have any questions.

723
00:44:07,680 --> 00:44:09,930
I'm going to be here tomorrow.

724
00:44:09,930 --> 00:44:13,620
I probably will be here
Saturday and Sunday.

725
00:44:13,620 --> 00:44:16,290
So if there's a last
minute question,

726
00:44:16,290 --> 00:44:20,910
just send me an email, and
I'm happy to invite you in,

727
00:44:20,910 --> 00:44:24,240
and we can answer your question.

728
00:44:24,240 --> 00:44:26,400
I should be here in the
afternoon, probably,

729
00:44:26,400 --> 00:44:29,190
on Saturday and Sunday.

730
00:44:29,190 --> 00:44:39,510
Now, I'd like to end the lecture
today by doing a demonstration.

731
00:44:39,510 --> 00:44:41,080
Actually, did I turn that off?

732
00:44:41,080 --> 00:44:42,930
I can show you this here.

733
00:44:42,930 --> 00:44:47,100
I'm going to do this
Briggs-Rauscher reaction.

734
00:44:47,100 --> 00:44:54,300
Actually, we're going to
make this iodomalonic acid.

735
00:44:54,300 --> 00:44:57,480
We're going to actually attach
an iodine to malonic acid.

736
00:44:57,480 --> 00:45:00,120
We're going to create
this in a beaker.

737
00:45:00,120 --> 00:45:01,980
The reason I'm showing
you this reaction

738
00:45:01,980 --> 00:45:06,720
is because it has everything
in it, including starch.

739
00:45:06,720 --> 00:45:09,000
And it has a lot of colors.

740
00:45:09,000 --> 00:45:12,000
And these colors are
things that we're

741
00:45:12,000 --> 00:45:16,140
going to talk about in the
next lecture, what starch does

742
00:45:16,140 --> 00:45:17,290
and how it works.

743
00:45:17,290 --> 00:45:21,540
And this is kind of
a preview to that.

744
00:45:21,540 --> 00:45:23,160
This reaction that
you're going to see

745
00:45:23,160 --> 00:45:28,410
was actually discovered by two
high school chemistry teachers.

746
00:45:28,410 --> 00:45:31,860
They're Briggs and Rauscher
from Galileo High School,

747
00:45:31,860 --> 00:45:34,680
my favorite city, San Francisco.

748
00:45:34,680 --> 00:45:39,370
So these guys came up with
this back in, I think, 1973.

749
00:45:39,370 --> 00:45:43,290
They published a paper in the
Journal of Chemical Education.

750
00:45:43,290 --> 00:45:48,690
And they had every scientist
in the country puzzled.

751
00:45:48,690 --> 00:45:50,940
And it took about
10 years to work out

752
00:45:50,940 --> 00:45:53,130
all the and sundry
reactions that

753
00:45:53,130 --> 00:45:56,140
are going on in this reaction.

754
00:45:56,140 --> 00:46:00,300
So I'm going to put on
some safety glasses.

755
00:46:00,300 --> 00:46:07,400
And what I'm going
to be doing is

756
00:46:07,400 --> 00:46:12,270
going to be mixing three
colorless solutions in here.

757
00:46:12,270 --> 00:46:14,280
This is my first one.

758
00:46:14,280 --> 00:46:17,580
And I'm going to use
kitchen chemistry, which

759
00:46:17,580 --> 00:46:20,668
means I'm kind of looking
at that scale over there

760
00:46:20,668 --> 00:46:21,960
and I'm going to pour these in.

761
00:46:32,080 --> 00:46:35,820
So let's put a little more.

762
00:46:35,820 --> 00:46:38,050
That's colorless, right?

763
00:46:38,050 --> 00:46:40,485
OK, next colorless solution.

764
00:46:55,610 --> 00:46:58,780
That's about right.

765
00:46:58,780 --> 00:47:02,120
And the final colorless
solution-- keep your eye on it.

766
00:47:10,480 --> 00:47:14,530
Oh my goodness, wow.

767
00:47:14,530 --> 00:47:15,940
It wasn't supposed to do that.

768
00:47:22,380 --> 00:47:24,690
What?

769
00:47:24,690 --> 00:47:25,590
Are you kidding me?

770
00:47:32,400 --> 00:47:33,440
What's going on here?

771
00:47:37,010 --> 00:47:38,450
Get your clock out.

772
00:47:38,450 --> 00:47:40,120
This is a clock reaction.

773
00:47:40,120 --> 00:47:41,630
You can keep time with this.

774
00:47:53,600 --> 00:47:56,770
So I'll give you a little hint.

775
00:47:56,770 --> 00:48:00,940
There iodide in there, I minus.

776
00:48:04,060 --> 00:48:06,550
And I minus is colorless.

777
00:48:11,560 --> 00:48:15,580
There is iodine in there,
and iodine is amber.

778
00:48:22,030 --> 00:48:27,520
When they're both
present, it's blue-black.

779
00:48:27,520 --> 00:48:30,610
And we're going to see why
that is in the next lecture.

780
00:48:36,650 --> 00:48:40,180
So there's a lot of
reactions going on in there.

781
00:48:40,180 --> 00:48:45,640
When these reactants react,
they form hypoiodous acid.

782
00:48:45,640 --> 00:48:50,890
And sometimes, the
hypoiodous acid actually

783
00:48:50,890 --> 00:48:54,170
oxidizes iodide to iodine.

784
00:48:54,170 --> 00:48:56,720
So you've got collarless
going to amber.

785
00:48:56,720 --> 00:49:00,650
But sometimes, there's so
much hypoiodous acid formed,

786
00:49:00,650 --> 00:49:02,520
you can't handle everything.

787
00:49:02,520 --> 00:49:05,690
And what happens is you
have a little bit of I

788
00:49:05,690 --> 00:49:08,300
minus and I2 present
at the same time.

789
00:49:08,300 --> 00:49:09,957
And you get blue-black.

790
00:49:09,957 --> 00:49:11,540
This is kind of the
color you're going

791
00:49:11,540 --> 00:49:13,250
to get when you
do your titrations

792
00:49:13,250 --> 00:49:15,710
and you add the
starch, because there

793
00:49:15,710 --> 00:49:19,670
is starch present in this.

794
00:49:19,670 --> 00:49:21,950
So I'm going to
leave you with that.

795
00:49:21,950 --> 00:49:26,000
And I'll see some of
you up in the lab.

796
00:49:26,000 --> 00:49:27,170
Yes, you have a question.

797
00:49:27,170 --> 00:49:29,120
AUDIENCE: [INAUDIBLE]

798
00:49:29,120 --> 00:49:32,630
JOHN DOLHUN: She just asked
me if this will ever stop.

799
00:49:32,630 --> 00:49:35,470
Can someone--
Hannah wants to know

800
00:49:35,470 --> 00:49:37,520
if this is going to ever stop.

801
00:49:37,520 --> 00:49:43,050
Who can tell me, anyone?

802
00:49:43,050 --> 00:49:43,550
Aisha?

803
00:49:43,550 --> 00:49:46,175
AUDIENCE: I feel like it won't,
because it's not releasing gas.

804
00:49:48,393 --> 00:49:50,810
JOHN DOLHUN: Aisha says it
probably won't because it's not

805
00:49:50,810 --> 00:49:52,700
releasing gas.

806
00:49:52,700 --> 00:49:54,320
But in a minute, it's going to.

807
00:49:54,320 --> 00:49:57,080
Iodine vapor is going to
start pouring out of it,

808
00:49:57,080 --> 00:50:00,470
and Tristan is going to carry
it up to the lab in a bucket

809
00:50:00,470 --> 00:50:02,780
quickly.

810
00:50:02,780 --> 00:50:10,700
But in answer to Hannah's
question is, will this stop?

811
00:50:10,700 --> 00:50:12,020
AUDIENCE: [INAUDIBLE]

812
00:50:12,020 --> 00:50:14,180
JOHN DOLHUN: Limiting
reagent, right?

813
00:50:14,180 --> 00:50:17,220
There's always a
limiting reagent.

814
00:50:17,220 --> 00:50:19,690
OK, see you.