SAMPLING AND ANALYSIS OF CRUDE GLYCERIN
APPARATUS
1. Pycnometer, Gay-Lussac type or any other suitable pycnometer, preferably 50 mL capacity. The pycnometer should be
equipped with a thermometer graduated in 0.1°C with a range of from 10°C to 40°C (e Figure 1). The thermometer should be calibrated against a National Institute of Standards and Technology (NIST) certified thermometer over the work-ing range of the thermometer.
2. Water bath regulated at the required temperature ±01°
REAGENTS
1. Water, freshly distilled and then cooled to a temperature slightly below the temperature at which the determination will be
made.
2. Acetone.
PROCEDURE
1. Carry out each weighing to the nearest 0.1 mg.
2. Bring the substance (either water or glycerin) to a temperature slightly below the temperature at which the determination
will be made.
Caution—During all testing operations, the test portion must be protected against loss of moisture by evaporation or gain of moisture due to the hygroscopic nature of glycerin.
3. Empty the pycnometer (Apparatus, 1), rin with acetone (Reagents, 2) and dry. After 2–3 minutes weigh it empty, but with
stopper and thermometer in place.
4. Fill the pycnometer with the substance (either water or glycerin), avoiding the formation of bubbles (e Notes, 3). Inrt the
thermometer. Rin the outside with distilled water (Reagents, 1). Immer the pycnometer in the water-bath (Apparatus, 2) at the temperature of measurement to a depth half way up the ground portion of the neck, leaving it there for 30 minutes.
5. While keeping the pycnometer in the water-bath, remove any excess liquid from the neck so that the level is exactly flush
with the end of the capillary tube in the neck of pycnometer.
6. Place the stopper on the neck of the pycnometer and remove the pycnometer from the water-bath and hold it for 1 minute
in a stream of water at a temperature below the required temperature. Dry the outside of the pycnometer with a lint-free
cloth. Leave to cool if necessary and wipe with a cloth lightly soaked in acetone.
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SAMPLING AND ANALYSIS OF CRUDE GLYCERIN
Ea 7-95 • D etermination of the Relative Density 20/20 in Air
7. After 2–3 minutes, reweigh the pycnometer. Calculate, by difference, the conventional mass of substance (water or glycerin) it contains (e Notes, 4).CALCULATIONS
1. Relative density 20/20 in air—The relative density 20/20 in air (d 20/20) is given by the formula:
d m
m 20/20=2
1
Where—
m 1 = the conventional mass in g, of water (Reagents, 1) contained in the pycnometer (Apparatus, 1) at 20°C as determined by Procedure;
m 2 = the conventional mass, in g, of glycerin contained in the pycnometer at 20°C, as determined by Procedure.
2. Mass per unit volume at temperature t —The mass per unit volume at temperature t(p t ), g/mL, is given by the formula:
p t m V t
=3
Where—
m 3 = the conventional mass of glycerin, in g, contained in the pycnometer at temperature t , as determined by Procedure;V t = the volume of the pycnometer at temperature t , in mL (e Notes, 5). Note —If the mass per unit volume has to be expresd in kg/m 3 (SI units), the value found has to be multiplied by 103. 3. Express the results to three decimal places.
PRECISION
1. Repeatability—Duplicate determination on the same day by the same analyst using the same apparatus should not differ by
more than 0.0002.
2. Reproducibility—Single determinations made in different laboratories should not differ by more than 0.0005.
NOTES
1. The relative density 20/20 in air is in current u for the qualification of purified glycerins. It is also a measure of g lycerol content.
T o convert the relative density in air to glycerol content, the T able of Bosart and Snoddy has been included. (T able 2). The conven-tional mass per unit volume of glycerins is ud to convert volumes to mass (not taking into account buoyancy due to air).
2. The expressions “relative density” (d ) and “specific gravity” are equivalent. When the term “relative density” includes, for
example, the notation 20/4, the measurement has been carried out at 4°C for the reference substance (water) and at 20°C for the substance to be examined (glycerins). The conversion d 20/20 to d 20/4 may be calculated using the following formula:
d 20/4 = d 20/20 × 0.99823
3. Water and test sample must be free of air bubbles. If bubbles are prent, they may be removed by centrifuging.
4. If it is necessary to carry out numerous determinations, it may be practical not to calibrate the pycnometer at each measure-ment, but merely to check that its mass and volume remain constant with time. The volume of the pycnometer (Apparatus, 1) at a given temperature t (V t ), in mL, is given by the formula:
Vt mt
p t =
(H O)2Where—
m 1 = the conventional mass, in g, of water (Reagents, 1)
contained in the pycnometer (Apparatus, 1 ) at the temperature t , as determined in Procedure; p t (H 2O) = the conventional mass per unit volume of water at temperature t , in g/mL
5. If the pycnometer is calibrated at 20°C, the volume the pycnometer at t °C can be calculated using the formula:
V t = V 20[1 + α(t − 20)]
天蝎座水瓶座
Where— V t = the volume of the pycnometer at t °C, in mL; V 20 = the volume of the pycnometer at 20°C, in mL; α = the cubic expansion coefficient of the glass of the pycnometer, in °C −1.Some values of α:
Boro-silicate glass D50: 10 × 10−6 °C −1Boro-silicate glass G20: 16 × 10−6 °C −1Sodium glass: 15 − 30 × 10−6 °C −1 REFERENCE
1. Industrial and Engineering Chemistry 19:506 (1927), Bosart and Snoddy Table.
SAMPLING AND ANALYSIS OF CRUDE GLYCERIN Ea 7-95 • D etermination of the Relative Density 20/20 in Air
Table 1
Water, conventional mass per unit volume p
t , (H
2
O) at temperature t.
(From Draft Proposal ISO/DP 6883-Doc. ISO/TC34/SC 11N 186)
t(°C) p t H2O(g/mL) t(°C) p t H2O(g/mL) t(°C) p t H2O(g/mL)
15 0.99807 32 0.99399 49 0.98746
16 0.99791 33 0.99367 50 0.98701
17 0.99774 34 0.99334 51 0.98656
18 0.99756 35 0.99300 52 0.98609
19 0.99737 36 0.99265 53 0.98563
20 0.99717 37 0.99230 54 0.98515
21 0.99696 38 0.99193 55 0.98467怎么更新系统
22 0.99674 39 0.99156 56 0.98419
23 0.99651 40 0.99119 57 0.98369
24 0.99627 41 0.99080 58 0.98319
25 0.99601 42 0.99041 59 0.98269
26 0.99575 43 0.99001 60 0.98213
27 0.99548 44 0.98960 61 0.98166
28 0.99520 45 0.98918 62 0.98114
29 0.99491 46 0.98876 63 0.98061
30 0.99461 47 0.98834 64 0.98007
31 0.99431 48 0.98790 65 0.97953
Table 2
Specific Gravity vs. Glycerol Concentration by Bosart and Snoddy a
五军营
100 1.26557 1.26532 1.26362 1.26201 1.26526 1.26501 1.26331 1.26170 99 1.26300 1.26275 1.26105 1.25945 1.26270 1.26245 1.26075 1.25910 98 1.26045 1.26020 1.25845 1.25685 1.26010 1.25985 1.25815 1.25655 97 1.25785 1.25760 1.25585 1.25425 1.25755 1.25730 1.25555 1.25395 96 1.25525 1.25500 1.25330 1.25165 1.25495 1.25470 1.25300 1.25140 95 1.25270 1.25245 1.25075 1.24910 1.25240 1.25215 1.25045 1.24800 94 1.25005 1.24980 1.24810 1.24645 1.24975 1.24950 1.24780 1.24615 93 1.24740 1.24715 1.24545 1.24380 1.24710 1.24685 1.24515 1.24350 92 1.24475 1.24450 1.24280 1.24115 1.24445 1.24420 1.24250 1.24085 91 1.24210 1.24185 1.24020 1.23850 1.24185 1.24155 1.23985 1.23825 90 1.23950 1.23920 1.23755 1.23585 1.23920 1.23895 1.23725 1.23560 89 1.23680 1.23655 1.23490 1.23320 1.23655 1.23625 1.23460 1.23295 88 1.23415 1.23390 1.23220 1.23055 1.23390 1.23360 1.23195 1.23025 87 1.23150 1.23120 1.22955 1.22790 1.23125 1.23095 1.22930 1.22760 86 1.22885 1.22855 1.22690 1.22520 1.22860 1.22830 1.22670 1.22495 85 1.22620 1.22590 1.22420 1.22255 1.22595 1.22565 1.22395 1.22230 84 1.22355 1.22325 1.22155 1.21990 1.22330 1.22300 1.22120 1.21965 83 1.22090 1.22055 1.21890 1.21720 1.22060 1.22030 1.21860 1.21695 82 1.21820 1.21790 1.21620 1.21455 1.21795 1.21765 1.21595 1.21430 81
1.21555 1.21525 1.21355 1.21190 1.21520 1.21500 1.21330 1.21165 80 1.21290 1.21260 1.21090 1.20925 1.21265 1.21235 1.21065 1.20900 79 1.21015 1.20985 1.20815 1.20655
78 1.20740 1.20710 1.20540 1.20380
77 1.20465 1.20440 1.20270 1.20110
76 1.20190 1.20165 1.19995 1.19840
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SAMPLING AND ANALYSIS OF CRUDE GLYCERIN
Ea 7-95 • D etermination of the Relative Density 20/20 in Air
Table 2 (continued)
Glycerol Apparent specific gravity True specific gravity 15/15°C 15.5/15.5°C 20/20°C 25/25°C 15/15°C 15.5/15.5°C 20/20°C 25/25°C 75 1.19915 1.19890 1.19720 1.19565 1.19890 1.19865 1.19700 1.19540 74 1.19640 1.19615 1.19450 1.19295
73 1.19365 1.19340 1.19175 1.19025
72 1.19090 1.19070 1.18900 1.18755
71 1.18815 1.18795 1.18630 1.18480
70 1.18540 1.18520 1.18355 1.18210 1.18515 1.18495 1.18330 1.18185 69 1.18260 1.18240 1.18080 1.17935
心脏病怎么治68 1.17985 1.17965 1.17805 1.17660
67 1.17705 1.17685 1.17530 1.17385
66 1.17430 1.17410 1.17255 1.17110
65 1.17155 1.17130 1.16980 1.16835 1.17135 1.17110 1.16960 1.16815 64 1.16875 1.16855 1.16705 1.16560
63 1.16600 1.16575 1.16430 1.16285
62 1.16320 1.16300 1.16155 1.16010
61 1.16045 1.16020 1.15875 1.15735
60 1.15770 1.15745 1.15605 1.15460 1.15750 1.15725 1.15585 1.15445 59 1.15490 1.15465 1.15325 1.15185
58 1.15210 1.15190 1.15050 1.14915
57 1.14935 1.14910 1.14775 1.14640
56 1.14655 1.14635 1.14500 1.14365
55 1.14375 1.14355 1.14220 1.14090 1.14360 1.14340 1.14205 1.14075 54 1.14100 1.14080 1.13945 1.13815
53 1.13820 1.13800 1.13670 1.13540
52 1.13540 1.13525 1.13395 1.13265封一
51 1.13265 1.13245 1.13120 1.12995
50 1.12985 1.12970 1.12845 1.12720 1.12970 1.12955 1.12830 1.12705 49 1.1271
0 1.12695 1.12570 1.12450
48 1.12440 1.12425 1.12300 1.12185
47 1.12165 1.12150 1.12030 1.11915
46 1.11890 1.11880 1.11760 1.11650
45 1.11620 1.11605 1.11490 1.11380 1.11605 1.11595 1.11475 1.11365 44 1.11345 1.11355 1.11220 1.11115
43 1.11075 1.11060 1.10950 1.10845
42 1.10800 1.10790 1.10680 1.10575
41 1.10525 1.10515 1.10410 1.10310
40 1.10255 1.10245 1.10135 1.10040 1.10240 1.10235 1.10125 1.10030 39 1.09985 1.09975 1.09870 1.09775
38 1.09715 1.09705 1.09605 1.09510
37 1.09445 1.09435 1.09335 1.09245大便多
36 1.09175 1.09165 1.09070 1.08980
35 1.08905 1.08895 1.08805 1.08715 1.08895 1.08885 1.08790 1.08705 34 1.08635 1.08625 1.08535 1.08455
33 1.08365 1.08355 1.08270 1.08190
32 1.08100 1.08085 1.08005 1.07925
31 1.07830 1.07815 1.07735 1.07660
30 1.07560 1.07545 1.07470 1.07395 1.07550 1.07535 1.07460 1.07385 29 1.07295 1.07285 1.07210 1.07135
28 1.07035 1.07025 1.06950 1.06880
27 1.06770 1.06760 1.06690 1.06625
26 1.06510 1.06500 1.06435 1.06370
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SAMPLING AND ANALYSIS OF CRUDE GLYCERIN
Ea 7-95 • D etermination of the Relative Density 20/20 in Air
Table 2 (continued)
Glycerol Apparent specific gravity True specific gravity 15/15°C 15.5/15.5°C 20/20°C 25/25°C 15/15°C 15.5/15.5°C 20/20°C 25/25°C 25 1.06250 1.06240 1.06175 1.06115 1.06240 1.06230 1.06165 1.06110 24 1.05985 1.05980 1.05915 1.05860
23 1.05725 1.05715 1.05655 1.05605
22 1.05450 1.05455 1.05400 1.05350
21 1.05200 1.05195 1.05140 1.05095
20 1.04935 1.04915 1.04880 1.04840 1.04930 1.04925 1.04875 1.04830 19 1.04685 1.04660 1.04630 1.04590
18 1.04435 1.04430 1.04380 1.04345
17 1.04180 1.04160 1.04135 1.04100
八百标兵奔北坡绕口令16 1.03930 1.03925 1.03885 1.03850
15 1.03675 1.03675 1.03635 1.03605 1.03670 1.03670 1.03630 1.03600 14 1.03425 1.03420 1.03390 1.03360
13 1.03175 1.03170 1.03140 1.03100
12 1.02920 1.02920 1.02890 1.02865
11 1.02670 1.02665 1.02640 1.02620
市场营销专业10 1.02415 1.02415 1.02395 1.02370 1.02415 1.02410 1.02390 1.02370
9 1.02175 1.02175 1.02155 1.02135
8 1.01935 1.01930 1.01915 1.01900
7 1.01690 1.01690 1.01675 1.01660
6 1.01450 1.01450 1.01435 1.01425
5 1.01210 1.01205 1.01195 1.01185 1.01205 1.01205 1.01195 1.01175
4 1.0096
5 1.00965 1.00955 1.00950
3 1.00725 1.00725 1.00700 1.00710
2 1.00485 1.00485 1.00480 1.00475
1 1.00240 1.00240 1.00240 1.00235
a References, 1.
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