1 00:00:01,930 --> 00:00:03,789 [PIANO MUSIC PLAYING] 2 00:00:24,002 --> 00:00:25,913 [SOFT GLISSANDO PLAYING] 3 00:00:29,090 --> 00:00:30,890 PROFESSOR: Volumetric techniques-- 4 00:00:30,890 --> 00:00:32,600 measuring, essentially. 5 00:00:32,600 --> 00:00:35,330 Have you ever added too much pepper to a recipe? 6 00:00:35,330 --> 00:00:37,310 I know, it's not so great afterwards, 7 00:00:37,310 --> 00:00:38,960 but it's an innocent mistake. 8 00:00:38,960 --> 00:00:41,030 But in the lab, you have to be sure to have 9 00:00:41,030 --> 00:00:42,480 precise measurements. 10 00:00:42,480 --> 00:00:47,020 So we're going to learn how to get those now. 11 00:00:47,020 --> 00:00:54,500 We'll be using the volumetric pipette, the burette, 12 00:00:54,500 --> 00:00:58,085 the volumetric flask, and the syringe. 13 00:01:01,630 --> 00:01:04,239 Now for some basic rules. 14 00:01:04,239 --> 00:01:07,990 First and foremost, keep all glassware clean. 15 00:01:07,990 --> 00:01:10,780 You want to be able to clearly read the markings on all 16 00:01:10,780 --> 00:01:11,800 your equipment. 17 00:01:11,800 --> 00:01:14,520 Therefore, keep it clean. 18 00:01:14,520 --> 00:01:18,750 Also, you always need to read at the bottom of the meniscus. 19 00:01:18,750 --> 00:01:20,640 The meniscus is the curved interface 20 00:01:20,640 --> 00:01:23,040 between the air and the liquid. 21 00:01:23,040 --> 00:01:25,320 You need to read at eye level and at the bottom 22 00:01:25,320 --> 00:01:29,680 of the meniscus in order to get a correct reading. 23 00:01:29,680 --> 00:01:32,800 Now for the basics of washing your equipment. 24 00:01:32,800 --> 00:01:35,860 First, use soap solution to clean it. 25 00:01:35,860 --> 00:01:38,080 Then rinse with tap water. 26 00:01:38,080 --> 00:01:42,470 Then rinse with distilled water, rinsing thoroughly each time. 27 00:01:42,470 --> 00:01:48,600 Finally, rinse with solvent if appropriate and let dry. 28 00:01:48,600 --> 00:01:51,041 Now let's cover the equipment. 29 00:01:51,041 --> 00:01:52,514 [SOFT GLISSANDO PLAYING] 30 00:01:54,970 --> 00:01:58,630 Pipettes are used to measure small quantities of volume, 31 00:01:58,630 --> 00:02:01,240 usually up to 10 milliliters. 32 00:02:01,240 --> 00:02:04,990 They work on the principle of creating a vacuum. 33 00:02:04,990 --> 00:02:08,460 Notice the pipette's gradation marks. 34 00:02:08,460 --> 00:02:11,400 Now let's learn all about the bulb. 35 00:02:11,400 --> 00:02:15,400 Here is the bulb of a volumetric pipette. 36 00:02:15,400 --> 00:02:19,720 Squeeze A, and then squeeze this section of the bulb, 37 00:02:19,720 --> 00:02:22,080 and you'll create a vacuum. 38 00:02:22,080 --> 00:02:23,820 If you want to suction up liquid, 39 00:02:23,820 --> 00:02:31,590 squeeze A. If you want to expel liquid, squeeze E. 40 00:02:31,590 --> 00:02:36,690 Here's a demonstration of creating and then releasing 41 00:02:36,690 --> 00:02:38,362 the vacuum. 42 00:02:38,362 --> 00:02:39,745 [ALARM SOUNDING] 43 00:02:41,130 --> 00:02:42,630 MALE PROFESSOR: Caution. 44 00:02:42,630 --> 00:02:46,440 Never use your mouth to suction up liquids. 45 00:02:46,440 --> 00:02:48,480 PROFESSOR: Now, for some basic pipetting. 46 00:02:51,040 --> 00:02:53,110 First you need to create a vacuum. 47 00:02:53,110 --> 00:02:55,930 Squeeze A and push in the bulb to do this. 48 00:02:58,480 --> 00:03:03,070 To draw up liquid, squeeze S. There it goes. 49 00:03:06,070 --> 00:03:09,190 And to expel your liquid, you then 50 00:03:09,190 --> 00:03:17,020 want to squeeze E. Down it goes. 51 00:03:17,020 --> 00:03:20,920 When you're all done, squeeze A again to release the vacuum. 52 00:03:24,430 --> 00:03:27,450 Now for filling a pipette. 53 00:03:27,450 --> 00:03:29,760 First, create a vacuum. 54 00:03:29,760 --> 00:03:33,120 Then draw up past the 0 mark. 55 00:03:33,120 --> 00:03:35,850 This is to coat the interior walls. 56 00:03:35,850 --> 00:03:38,730 Then expel all your liquid. 57 00:03:38,730 --> 00:03:41,610 Draw up past the 0 mark once again, 58 00:03:41,610 --> 00:03:46,650 but this time, slowly release to the 0 mark. 59 00:03:46,650 --> 00:03:52,524 Or you may choose to slowly draw up to the 0 mark instead. 60 00:03:52,524 --> 00:03:53,988 [ALARM SOUNDING] 61 00:03:54,970 --> 00:03:57,070 MALE PROFESSOR: Caution-- never allow 62 00:03:57,070 --> 00:03:59,860 any liquid to enter the bulb. 63 00:03:59,860 --> 00:04:02,560 PROFESSOR: Finally, cleaning the pipette-- 64 00:04:02,560 --> 00:04:05,860 you want to rinse with soap and water and solvent as usual. 65 00:04:05,860 --> 00:04:08,743 But remember, don't get anything in the bulb. 66 00:04:08,743 --> 00:04:10,675 [SOFT GLISSANDO PLAYING] 67 00:04:12,610 --> 00:04:16,970 Volumetric flasks are used to dilute solutions. 68 00:04:16,970 --> 00:04:19,870 What would we need for this process? 69 00:04:19,870 --> 00:04:26,710 The flask, powder or concentrated solution instead, 70 00:04:26,710 --> 00:04:30,160 a funnel and stirring rod for guiding in the solution, 71 00:04:30,160 --> 00:04:35,190 solvent for rinsing, solvent for pouring in and diluting, 72 00:04:35,190 --> 00:04:38,430 and finally a pipette to add the last drops up 73 00:04:38,430 --> 00:04:41,010 to the gradation mark. 74 00:04:41,010 --> 00:04:44,290 If you're going to make the solution from powder, 75 00:04:44,290 --> 00:04:48,610 uncap the flask and add your whey powder into the flask 76 00:04:48,610 --> 00:04:51,680 carefully. 77 00:04:51,680 --> 00:04:55,520 Alternatively, you may choose to use concentrated solution 78 00:04:55,520 --> 00:04:56,570 instead. 79 00:04:56,570 --> 00:04:58,850 Use a funnel and possibly a stirring rod 80 00:04:58,850 --> 00:05:00,695 to guide the solution into the flask. 81 00:05:04,730 --> 00:05:07,150 Now it's very important that you rinse 82 00:05:07,150 --> 00:05:09,640 with the appropriate solvent. 83 00:05:09,640 --> 00:05:12,010 In our case, we're diluting with water. 84 00:05:12,010 --> 00:05:14,590 But you may be using something else. 85 00:05:14,590 --> 00:05:19,330 Be sure to rinse the beaker, the stirring rod, and the funnel, 86 00:05:19,330 --> 00:05:23,450 three times each. 87 00:05:23,450 --> 00:05:25,715 Add these washings directly to the flask. 88 00:05:29,140 --> 00:05:30,655 Now for adding the solvent. 89 00:05:37,250 --> 00:05:40,430 Take your solvent and fill the flask half full. 90 00:05:46,160 --> 00:05:50,000 Swirl or invert to facilitate the solution. 91 00:05:50,000 --> 00:05:54,680 Then add more solvent, but be sure not 92 00:05:54,680 --> 00:05:56,390 to fill to the gradation mark. 93 00:06:00,460 --> 00:06:04,420 Notice here how we didn't fill it up to the mark. 94 00:06:04,420 --> 00:06:06,700 Let the flask sit to allow drainage 95 00:06:06,700 --> 00:06:09,020 from the interior walls. 96 00:06:09,020 --> 00:06:10,460 [ALARM SOUNDING] 97 00:06:10,960 --> 00:06:14,710 MALE PROFESSOR: Important-- make sure your solute is completely 98 00:06:14,710 --> 00:06:17,290 dissolved. 99 00:06:17,290 --> 00:06:19,510 PROFESSOR: Here is some undissolved solute. 100 00:06:19,510 --> 00:06:23,110 Make sure you swirl and invert to dissolve this before you 101 00:06:23,110 --> 00:06:25,210 continue with your dilution. 102 00:06:25,210 --> 00:06:27,790 After you know all is dissolved, and you've 103 00:06:27,790 --> 00:06:30,790 allowed 1 minute for drainage, use a pipette 104 00:06:30,790 --> 00:06:33,310 to add the last few drops of solvent up 105 00:06:33,310 --> 00:06:34,450 to the gradation mark. 106 00:06:40,930 --> 00:06:44,560 And finally, be sure to swirl or invert. 107 00:06:44,560 --> 00:06:47,050 You'll notice that the bottom of the meniscus lines 108 00:06:47,050 --> 00:06:50,340 up with the gradation mark. 109 00:06:50,340 --> 00:06:52,200 Now, for storage. 110 00:06:52,200 --> 00:06:54,810 Use a clean, dry storage bottle. 111 00:06:54,810 --> 00:06:58,860 You may choose to rinse it with a small amount from the flask. 112 00:06:58,860 --> 00:07:02,580 Swirl and invert the flask to make sure it's all dissolved, 113 00:07:02,580 --> 00:07:05,040 then pour it into the storage bottle. 114 00:07:09,320 --> 00:07:13,860 Be sure to cap firmly before setting aside. 115 00:07:13,860 --> 00:07:15,480 Finally, cleaning the flask. 116 00:07:18,440 --> 00:07:20,710 Wash with soap and water, as usual. 117 00:07:20,710 --> 00:07:23,690 And if desired, clamp upside-down to facilitate 118 00:07:23,690 --> 00:07:25,052 drying. 119 00:07:25,052 --> 00:07:27,410 [SOFT GLISSANDO PLAYING] 120 00:07:27,410 --> 00:07:30,350 Burettes are used to measure and precisely dispense 121 00:07:30,350 --> 00:07:33,890 small quantities, as seen here in titrations. 122 00:07:36,530 --> 00:07:39,590 Let's address the proper hand position. 123 00:07:39,590 --> 00:07:42,440 Wrap your hand around the burette, as shown. 124 00:07:42,440 --> 00:07:45,680 Gently pushing forward the top portion with your forefinger 125 00:07:45,680 --> 00:07:47,780 allows titrant to flow. 126 00:07:47,780 --> 00:07:50,270 Gently pushing forward the bottom portion 127 00:07:50,270 --> 00:07:55,010 with your middle finger seizes the flow of titrant. 128 00:07:55,010 --> 00:07:56,480 Now, for filling the burette. 129 00:08:00,430 --> 00:08:03,690 Here is your titrant. 130 00:08:03,690 --> 00:08:08,130 Take your burette and add a few milliliters of titrant to it. 131 00:08:12,080 --> 00:08:14,420 Then tilt and rotate your burette 132 00:08:14,420 --> 00:08:18,180 to coat the interior walls with titrant. 133 00:08:18,180 --> 00:08:20,610 Allow all the titrant to drain out. 134 00:08:23,340 --> 00:08:26,640 Then fill your burette to above the 0 mark. 135 00:08:29,420 --> 00:08:31,670 But wait, we need to get rid of air bubbles. 136 00:08:34,330 --> 00:08:37,039 So what's wrong with this burette? 137 00:08:37,039 --> 00:08:38,549 Well, you guessed it. 138 00:08:38,549 --> 00:08:40,470 There are air bubbles in the tip. 139 00:08:40,470 --> 00:08:42,350 This could be a major problem. 140 00:08:42,350 --> 00:08:44,810 To get rid of air bubbles, quickly rotate 141 00:08:44,810 --> 00:08:46,640 the valve back and forth, allowing 142 00:08:46,640 --> 00:08:50,850 small amounts of liquid to pass through intermittently. 143 00:08:50,850 --> 00:08:52,950 Look, no more air bubbles. 144 00:08:52,950 --> 00:08:57,730 Now that they're gone, we can proceed to drain the burette. 145 00:08:57,730 --> 00:09:00,670 Remember, you filled it to above the 0 mark. 146 00:09:00,670 --> 00:09:04,210 Now you'll slowly drain it to the 0 mark. 147 00:09:04,210 --> 00:09:07,000 But you don't have to reach it exactly. 148 00:09:07,000 --> 00:09:10,420 Just make sure you record the starting value, regardless 149 00:09:10,420 --> 00:09:14,020 of where it is, before you do anything else. 150 00:09:14,020 --> 00:09:17,980 Now let's learn about proper meniscus reading. 151 00:09:17,980 --> 00:09:20,560 Remember to read at the bottom of the meniscus 152 00:09:20,560 --> 00:09:23,950 and to avoid parallax, which is inaccurate reading, 153 00:09:23,950 --> 00:09:26,170 always read at eye level. 154 00:09:26,170 --> 00:09:31,990 Here, the burette can easily be read as 3.50 milliliters. 155 00:09:31,990 --> 00:09:34,630 But what happens if you read from below? 156 00:09:34,630 --> 00:09:39,610 Well, it's 3.55 milliliters-- more than the actual amount. 157 00:09:42,800 --> 00:09:47,440 And if we read from above, it appears as 3.45 milliliters-- 158 00:09:47,440 --> 00:09:49,900 less than the actual amount. 159 00:09:49,900 --> 00:09:52,000 Moral of the story-- 160 00:09:52,000 --> 00:09:56,400 avoid parallax and read at eye level. 161 00:09:56,400 --> 00:09:58,320 Now, cleaning the burette. 162 00:10:01,200 --> 00:10:04,770 Use a long burette brush, as shown here. 163 00:10:04,770 --> 00:10:07,350 Wash with soap and water, as usual. 164 00:10:07,350 --> 00:10:11,544 And make sure that you wash through the tip. 165 00:10:11,544 --> 00:10:14,060 [SOFT GLISSANDO PLAYING] 166 00:10:14,060 --> 00:10:18,510 Syringes are used to measure and transfer very small quantities, 167 00:10:18,510 --> 00:10:21,230 such as those in microliters. 168 00:10:21,230 --> 00:10:23,645 So let's explore transfer via the syringe. 169 00:10:26,870 --> 00:10:31,010 Take your syringe, and with a curved needle, as shown here, 170 00:10:31,010 --> 00:10:35,390 draw up more solution than you actually need. 171 00:10:35,390 --> 00:10:37,730 You'll have an air bubble in your barrel. 172 00:10:37,730 --> 00:10:39,710 Tap it until it reaches the top. 173 00:10:44,210 --> 00:10:46,400 There's the air bubble at the top. 174 00:10:46,400 --> 00:10:49,760 Now expel some solution until you get to the amount 175 00:10:49,760 --> 00:10:52,720 that you actually need. 176 00:10:52,720 --> 00:10:54,820 After you expel some of the solution, 177 00:10:54,820 --> 00:10:56,860 you've pushed out the air, so your needle 178 00:10:56,860 --> 00:10:58,840 is entirely full of solution. 179 00:10:58,840 --> 00:11:02,140 And there should be a little drop at the end. 180 00:11:02,140 --> 00:11:04,660 In order not to lose anything from the needle, 181 00:11:04,660 --> 00:11:08,830 you need to withdraw a cushion of air. 182 00:11:08,830 --> 00:11:11,095 Now you're ready for transfer. 183 00:11:11,095 --> 00:11:13,300 Transfer the solution to the receiving vessel. 184 00:11:15,940 --> 00:11:19,210 But wait, even though you think you've transferred it all, 185 00:11:19,210 --> 00:11:21,940 you still have liquid in your needle. 186 00:11:21,940 --> 00:11:25,200 You need to expel this excess liquid. 187 00:11:25,200 --> 00:11:28,590 Invert your syringe, and by withdrawing and releasing 188 00:11:28,590 --> 00:11:31,290 the plunger, get rid of the excess liquid 189 00:11:31,290 --> 00:11:34,680 by pushing it out. 190 00:11:34,680 --> 00:11:36,810 Finally, cleaning the syringe. 191 00:11:36,810 --> 00:11:41,010 Before washing, disassemble the syringe into its components-- 192 00:11:41,010 --> 00:11:44,250 needle, barrel, and plunger. 193 00:11:44,250 --> 00:11:46,830 Wash with soap and water separately. 194 00:11:46,830 --> 00:11:49,050 Rinse with solvent and allow to dry. 195 00:11:54,010 --> 00:11:58,920 Now that you have the skills, go forth and measure. 196 00:11:58,920 --> 00:12:01,500 Remember, this video is intended to help 197 00:12:01,500 --> 00:12:04,410 you prepare for lab by providing a demonstration 198 00:12:04,410 --> 00:12:07,110 of the proper experimental technique. 199 00:12:07,110 --> 00:12:09,060 It is not intended as a replacement 200 00:12:09,060 --> 00:12:13,110 for reading your lab manual or the supplementary material. 201 00:12:13,110 --> 00:12:15,510 In order to become a great experimentalist, 202 00:12:15,510 --> 00:12:17,940 it is important that you understand both theory 203 00:12:17,940 --> 00:12:19,380 and technique. 204 00:12:19,380 --> 00:12:20,640 Now it's your turn. 205 00:12:20,640 --> 00:12:22,430 Good luck.