I S D U S T R I A L AA4TD ENGINEERI,VG CHEMISTRY
474
fications, but are not exactly the same as those adopted as standard by the National Association of Glue Manufacturers :6 Capacity Height over all Height of body of bottle Inside diameter of body Outside diameter of body Requires No. 9 rubber stopper
100 cc. 65 mm. 50 mm. 55 mm. 64 mm.
Xinety-eight cubic centimeters of redistilled water were then added to the gelatin and the contents stirred thoroughly with a metal rod. This resulted in a 1 to 14 dispersion, which proved very satisfactory for all the gelatin under examination. The samples were then placed in a cooling box a t a temperature of 10" to 15" C. and allowed to soak for 7 to 8 hours. After this soaking period the samples were put in a melting bath the temperature of which was not allowed to exceed 70" C., and the gelatins were then brought to 62" C. in about 15 minutes. The samples were cooled in the air to about 35" C. and then placed in a constant-temperature chill bath at 10" C. for 16 to 18 hours. The samples then were removed from the chill bath, and the jelly strength was determined with the Bloom gelometer, according to the method adopted by the National Association of Glue Manufaeturersa6 All the samples of gelatins were run in duplicate and carried out under identical conditions. Determination of pH Values The gelatin dispersions were made up in the same general manner as for the gold numbers, with the exception of the concentration, which in this case was 0.5 per cent. The p H measurements were made in duplicate, using the Clark electrode assembly with motor-driven shaker, hydrogen electrodes, and Leeds and Northrup Type K potentiometer. Results
The experimental results are presented in the accompanying table. Twenty-three different gelatins of varying grades showed very slight differences in gold numbers. The gold numbers ranged from 0.0085 with samples ill and HI to 0.015 with sample A+ 6
TEIISJ O U R X A L , 16, 310 (1974).
T'ol. 19, No. 4
Jelly Strengths, Gold Numbers and pH Values of Commercial Geiatins JELLY STRENGTH GOLD SAMPLE (BLOOM) NUMBER PH 268 0,0085 A1 4.7 181 0.0090 4.0 A2 130 0.0100 A3 6.3 58 5.7 A4 0.0150 0.OORO 4.0 339 BI 259 0.0100 Bz 4.0 246 0.0125 3.99 B3 0.0105 300 C1 4.3 103 4.05 c2 0.0115 189 0.3 Di 0.0100 113 5.95 0.0140 Dz 21 8 5.75 0.0090 EI 132 6.30 0.0097 E2 247 5.95 0.0094 A 170 6.70 0.0099 Fz 146 6.1 0.0100 Fa 241 5.7 0.0092 GI 150 0.0090 5.8 G2 5.75 0.0095 33 G3 265 5.9 Hi 0.0085 H? 5.6 70 0.0100 251 4.4 I1 0,0099 170 I2 4.85 0.0130
The jelly strength values varied from 33 with sample G3 to 339 with sample B1. Sample Ad with the largest gold number showed a low jelly-strength value of 58 and a p H of 5.7. The gelatin showing the lowest jelly strength value (G3) had a gold number of 0.0095, which was very close to the gold number of the gelatin with the highest jelly strength value, BI, its gold number being 0.0090. There was a considerable difference in jelly strength between the various grades of any one manufacturer. The jelly strength values showed large variations between the similar grades, so-called, of different manufacturers. The high-grade gelatin of manufacturer B1 had a jelly strength of 339, whereas the high-grade gelatin of manufacturer D, had a jelly strength of 189. The pH values ranged from 3.99 in case of sample BS to 6.70 with sample F2. Conclusion
Judging from the results obtained in this investigation, there is no direct relation between jelly strength, gold number, and the hydrogen-ion concentration of gelatins used in the ice cream trade.
Properties of Diethylene Glycol' By Wm. H. Rinkenbach PITTSBURGH
EXPERIMENT STA'CIOX, U. s. BUREAUO F
ECENT developments in the manufacture and use of ethylene glycol2 and its dinitrate3 insure a corresponding interest in derived or homologous compounds. A study of the dinitrate of diethylene glycol in the Explosives Chemical Laboratory of the Bureau of Mines necessitated the purification of a quantity of the diethylene glycol, and a search of the literature revealed a striking lack of fundamental data for this compound. As it appears highly probable that diethylene glycol, CH,OH. CH,. 0.CH, . CH,OH, will assume some importance in the explosives industry in the near future, it was considered desirable to study the chief physical properties of the pure compound, and the results of such a study are given in this paper. Preparation Wurtz4 prepared diethylene glycol by treating ethylene
R
1
Received January 27, 1927.
Published with approval of the Director,
M I N E S , PITTSBURGH,
PA.
oxide with water and also6 from ethylene oxide and glycol. Lourenco6 used glycol with ethylene dibromide or bromohydrin. Mohs' heated monosodium glycollate with glycol monoacetate a t 130-140" C. for 12 hours. At present it can be obtained on a large scale by a process similar to that used in the manufacture of ethylene glycol. The material used by the writer was supplied by the Carbide and Carbon Chemicals Corporation as a mixture of diethylene glycol with about 5 per cent of ethylene glycol, and perhaps some tri- and tetraethylene glycols. PURIFICATION-1650 cc. of this material were distilled under reduced pressure. The first fraction of 480 cc. was discarded. The second fraction of 1000 cc. was refractionated by freezing and gave a portion having a volume of 700 cc. that was used for subsequent work. Analysis gave: C, 45.0 per cent (calcd. 45.26); H, 9.6 per cent (calcd. 9.5).
1 ) . S. Bureau of Mines. 2
3 4
Taylor and Rinkenbach, THIS JOURNAL, 18, 676 (1926). Rinkenbach, Ibid., 18, 1195 (1926). C o m b f . r e n d . , 49, 813 (1859).
5 6
7
A n n . c h i m , [31 69, 317 (1863). I b i d , [3] 67, 257 (1863). Z . Chem., 1866, 495; Chem. Z e n f r . , 1866, 865; Jahresbev., 1866, 505.
IdVDUSTRIAL .4ND ENGIilrEERIA'G CHEMISTRY
April, 192T
Physical Properties
COLOR-The crude material possessed a distinctly bluish tint. but the purified material retained none or a very slight trace of this; it was not perceptible when a layer 6 inches deep was viewed by transmitted white light. ODOR-Diethylene glycol is odorless. Tasm-The pursed compound was found to possess a slightly sweet, somewhat burning taste. DENSITY--WUrtZ6 reported the density of diethylene glycol as 1.132 a t 0" C. By means of a Westphal balance, a cylinder containing about 125 cc. of the material, a 1-liter beaker as a constanttemperature bath, and a calibrated thermometer, thirty determinations of specific gravity at temperatures between 1.7" and 33" C. were made. When plotted, they were found t o give a straight line, from which the following values were read off: TEMPERATVRE
c.
SP.GR. C.) 1.1318 1.1283 1.1248
(rO/15O
0.0 3.0
10.0 15.0
1.1212
TEXPERATURE O
c.
The value obtained for 0" C. checks T-ery well with that given by R u r t z . FREEZIXG POI ST-^^ cc. of pure diethylene glycol were placed in a transparent Dewar flask of 50 cc. capacity and with a long, narrow neck. A calibrated thermometer reading from -36" t o +54" C. in 0.2-degree divisions and a copperwire stirrer were used. The bulb of the Dewar flask was immersed in a cooling bath of acetone and carbon dioxide snow. It was found that, although stirred continuously, the material supercooled before freezing, in one case to -25' C. Freezing point values of -10.55" and -10.35' C. (average -10.45' j= 0.05" C.) were obtained, as compared with from -17.4' to -11.5' C. for glycol.2 YAPORPRESSURE-This was determined by boiling under reduced and atmospheric pressures. Temperatures were read by means of calibrated, short-stem thermometers immersed in the vapor. Pressure readings were direct to 0.5 mm. of mercury. The train of apparatus consisted of distilling flask, condenser, manometer, receiving flask, 20-liter reservoir, and pump. It was found that excessive bumping and fluctuations in temperature readings resulted when heating in the usual way, so dried air was bubbled slowly through the liquid in the distilling flask in order to promote even ebullition. I n all, eighty-three readings of temperature and pressure mere taken and the values, when plotted, were found to give a smooth, continuous curve. From this the following values were read off: 'rEIP.
C.
130.0 135.0
140.0 146.0 148.5 150.0 155.0 160.0 165.0
PRESSURE
Hg
.\3m
8 12 16 21 25 27 34 43 54
TEMP. C. 170.0 175.0 180.0 185.0 190.0 195.0 200.0 205.0
PRESSURE
Mm. Hg 66 80 96 116 135 165 195 228
TEVP C 210.0
215.0 220.0 225.0 230.0 235.0 240.0 243.0
vapor pressure curve derived as stated above is extrapolated to a pressure of 760 mm., a value of 244.5" C. is obtained for the boiling point under standard pressure. This extrapolation includes the value obtained as the boiling point under atmospheric pressure, which was determined with no air bubbling through the liquid. VrscosITY-The viscosity of diethylene glycol was determined by means of a calibrated viscometer of the pipet, type. For purposes of comparison, similar determinations were made for ethylene glycol; only one value (0.1733 a t 25" C.)s for this substance a t ordinary temperature is known. The results obtained, expressed in c. g. s. units, follow: TEMP5R4TURE
C.
l5,O 17.5 20.0 22.5 25.0 27.0
ETHYLENE GLYCOL
DIETHYLENE GLYCOL Seconds Potses 138.0 0.50 122.3 0.44 110,o 0.38 100.5 0.33 91.8 0.30 85.5 0.27
.'econds 86.0 80.1 54.9 70.9 67.0 64.2
Poises 0.26 0.23 0.21 0.19
0.17 0.16
SP.GR. (r0/15" C . ) 1,1177 1,1141 1.1106 1.1071
20.0 25.0 30.0 35.0
475
PRESSURE
M m . Hg 268 316 370 430 $99 ,377 669 734
The boiling point value under a pressure of 25 mm. is given for purposes of comparison, as values for the tetra-, penta-, and hexaethylene glycols6 are given under this pressure. When the boiling points of these three substances, glycol, and diethylene glycol under a pressure of 25 mm. are plotted with the number of ethylene groups, a straight line results. According t o this, triethylene glycol, which has not been studied as yet, should boil a t about 190" C. under 25-mm. pressure. BOILIKGP o ~ s ~ - W u r t zstated ~ that the boiling uoint of diethylene glycol is about 250" C. When the boil& point-
These values show that diethylene glycol is considerably more viscous than ethylene glycol, the viscosity of the former closely approximating that of nitroglycerin. REFRACTIVEIxmx-The refractive index of diethylene glycol was observed a t thirty-eight points between 8" and 40" C. by means of a water-jacketed Zeiss refractometer employing sodium light and a calibrated thermometer. The values were plotted against temperature readings and found to represent a straight-line function. From this the following values were read off a t regular temperature intervals: REFRACTIVE INDEX
TEMPERATURE
c.
0.0 5.0 10.0 15.0
20.0
REFRACTIVE TEXPER.ATURE O
1.4334 1.4619 1.4504 1,449n 1.44i5
c.
25.0 30.0 35.0 40.0
INDEX
1.4461 1,4446 1.4131 1.4417
The refractive index of diethylene glycol is seen to be approximately the same as that of ethylene glycol, found2 to be 1.4311 a t 20" C. HEAT OF ComuwIox-Calorimetric determinations of the heat of combustion of diethylene glycol gave the following results: Cal / g u m 5335.6 5341
At constant volume At constant pressure
Kg cal /gram mol 566.11 566 69
These values are higher than those for glycol:2 283.293 kg. calories a t ordinary pressure as found by Louguinine,g 281.700 kg. calories a t constant pressure as given by Stohmann and Langbein,loand 282.2 kg. calories at constant pressure as reported by Parks and Kelly." HEATOF FoR~faTIoN-Calculation from the above values for heat of combustion of diethylene glycol gives the following values for heat of formation: Cal./gtam 1404 3 1398 9
At cowtant volume At constant pressure
Kg. cal./gram mol 149.00 148 42
HEATOF VAPORIZATION-Byusing data furnished by the vapor-pressure curve, the latent heat of vaporization a t the boiling point was calculated by the CIausius-Clapeyron equation and found to be approximately 150 calories per gram. This is much lower than the value of 190.9 calories per gram reported by Louguinine'* for glycol. HEAT OF DILuTrox-This was found to be positive, as is Z . phylik. Chem , 61, 732 (1905). Ann (him.. BO. 558 (1880). 10 J . prakl. Chem., 45, 305 (1892). " J . Am. Chem. Sac., 41, 2089 (1925). 12 Ann. chim., 171 26, 234 (1902). 8
9
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I X D USTRIAL AND ENGINEERING CHEMISTRY
476
generally the case with alcohols and glycols. It is probable that, like ethylene glycol, diethylene glycol forms a molecular complex with water, and this has a positive heat of solution. SOLUBILITY-At ordinary temperatures diethylene glycol was found to be freely miscible with water, methanol, ethanol, ethylene glycol, glacial acetic acid, acetone, furfuraldehyde, pyridine, glycol diacetate, chloroform, nitrobenzene, and aniline. It is immiscible with ether, benzene, toluene, carbon bisulfide, and carbon tetrachloride. An attempt to determine the molecular weight of diethylene glycol with benzene as a solvent indicated a solubility of 0.51 gram of the former in 100 grams of the latter a t 0" C. INFLAMMABILITY-Like glycol, diethylene glycol is nonflammable in the air a t ordinary temperatures. If, however, each is slowly heated in a shallow dish, glycol becomes in-
Vol. 19, No. 4
flammable in the air a t a temperature of 100" C. and diethylene glycol a t 130" C. Each burns with a clear, bluish flame. HYGRoscoPIcITY-Diethylene glycol is very hygroscopic and appears to be even more so than ethylene glycol. A sample in a flat vessel was placed in a closed space over water a t room temperature and found to absorb more than its own weight of water in 9 days. De Forcrand foundI3 that ethylene glycol appeared to reach a maximum after absorbing 60 per cent of its own weight in 2 weeks. STABILITY-Admixture with water does not appear to hydrolyze diethylene glycol. Determinations of molecular weight with water as the solvent in an 8 per cent solution gave results of 99.3 and 118.8, which would indicate that no hydrolysis to ethylene glycol had taken place. 13
Comfit. rend., 132, 688 (1901).
Viscosity of Cellulose Solutions' Modifications in Small's Cuprammonium Method By C. R. Genung SOUTHERN CHEMICAL COTTON Co., CHATTANOOGA, TENN.
HE increasing use of cellulose as a raw material in the
T
industries has made manufacturers, especially those making nitrocellulose, realize the importance of a reliable method for determining its viscosity. The most accurate method so far developed which is applicable to all grades of cellulose is that described by Small.2 He uses a cuprammonium solution containing 3.0 * 0.2 per cent copper by weight and 165 grams of ammonia per liter, and his cellulose solution contains 2.5 or 5 grams of cotton in 97 cc. of solution, depending on the probable viscosity of the cellulose under examination. The cuprammonium solution is made by bubbling air up through a tower containing clean copper turnings over which 28 per cent ammonia 8
Received December 31, 1925. Resubmitted January 3, 1927. THISJOURNAL,17, 515 (1925).
containing 1 per cent sucrose is allowed to trickle. To fill the cellulose bulb with the cuprammonium solution the vacuum is created by means of a mercury reservoir similar to that used in gas analysis. The method proposed by the writer is a modification of Small's procedure, which gives greater ease in manipulation and increased accuracy of results. The vacuum is created by means of a filter pump and the air is removed from the bulb by repeatedly washing with hydrogen. Electrolytic hydrogen of 99.6 per cent purity gives excellent results. Note-If a Kipp generator is used for the generation of hydrogen, it will be necessary to use an elevated reservoir for the storage of the solvent.
The apparatus has been further simplified by replacing the cuprammonium storage bulb and buret by a measuring pipet, filled by using hydrogen under a pressure of 50 to 75 mm. of mercury. By enlarging one end of the dissolving bulb so that it takes a No. 4 rubber stopper the time required to fill the bulbs with the weighed cotton sample is shortened. I n the writer's experience greater - accuracy is obtained by limiting the range of copper concentration of the cuprammonium solution to between 2.95 and 3.05 per cent by weight. Except for these modifications the procedure is similar to that given by Small. The modified apparatus is shown in the accompanying figure. Viscosities of C e l l u l o s e - C u p r a m m o n i u m S o l u t i o n s by Original a n d Modified S m a l l M e t h o d
.
SAMPLE
1 2 3 4 5
Apparatus f o r Filling Dissolving Bulbs f o r U s e with Hydrogen u n d e r Pressure
MODIFIED METHOD (1) (2)
5 25 84 176 680
5 24 84 172 720
ORIGINALMETHOD (1) (2) 6
24 89 167 671
6 27 86 162 640
I n order to compare the accuracy of the two procedures, 2.5-gram samples were dried and the viscosities of portions of each sample determined by both methods. The figures in the table show not only the relative accuracy of the two methods, but also that the results of two determinations of the modsed method agree more closely than those by the original method. The higher viscosities by the modified method are due to the complete removal of oxygen by this method.
