IXDUSTRIAL AND ENGIiVEERING CHEMISTRY
April, 1927
and the United Kingdom together take about one-half the exports. The average valuation of exports in 1926 was $22.51 per barrel, as against $16.11 in 1925. Spirits of turpentine were exported to the extent of 11,587,000 gallons, practically the same as in the year before. The value was $10,636,000, about 6 per cent less than in 1925. Imports of gums, resins, and balsams continued to increase in 1926, amounting to a value of $34,048,000 against 330,751,000 in 1925. The largest single item in point of value was shellac, the total quantity of which was 31,296.000 pounds,
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50 per cent more than in 1925. The value, however, totaling $10,515,000, was but little higher than in the year before. Both dammar, 15,156,000 pounds, and kauri, 5,456,000 pounds, were well above the 1925 imports. Synthetic camphor imports increased from 1,835,000 pounds valued a t $921,000 in 1925 to 2,944,000 pounds valued a t 81,558,000 in 1926, all from Germany. Natural crude camphor imports were 2,019,000 pounds, valued a t Sl,l58,000, somewhat less than in 1926, and refined 1,170,000 pounds valued at $783,000, also a decrease.
Commercial Gelatins‘ Their Jelly Strength, Gold Number, and Hydrogen-Ion Concentration By Paul Serex and M. W. Goodwin MASSACHUSETTS AGRICULTURAL COLLEGE,
D
.4MHERSf,
MASS.
*THIS J O C R X A L , 15, 699 (1921).
distilled water mere heated in a 400-500-cc. Pyrex beaker. During the heating, 2.5 cc. of a AuCls. HCl. 3Hz0 solution (6 grams per liter) and 3.5 cc. of an 0.18 N potassium carbonate solution were added. The resultant solution was then heated to the boiling point, and was constantly stirred to insure uniformity. 4 s soon as the solution started to boil, one or two drops of a 40 per cent solution of formaldehyde were added, the solution being stirred rapidly all this time. Upon the appearance of a red coloration the solution was removed from the heater and allowed t o cool. A sufficient quantity of this red gold sol was prepared, and thoroughly mixed, so that the necessary number of determinations might be made without further preparation of new samples. Gold numbers vary with the nature and concentration of gold sol and the protective colloid. The values are comparative only, the hydrophile with the lower gold number being the better protective colloid. The gold number, which represents the relative protective power, is defined by Zsigmondy5 as the number of milligrams of a protective colloid that just fails to protect 10 cc. of a colloidal gold sol against precipitation by 1 cc. of a 10 per cent sodium chloride solution. Determination of Gold Number One gram of gelatin was added to 500 cc. of conductivity water and heated to 75” C. in 20 minutes. It was allowed to cool to about 38” C. and then aged a t a constant temperture for exactly 24 hours. From this solution the required dilutions were prepared. Then to absolutely clean glass tubes was added 1 cc. of the various dilutions-i. e., 0.1, 0.01, and 0.001 mg., etc.-and to each of these were added 10 cc. of the gold hydrosol. Each tube was thoroughly shaken and allowed to stand 3 minutes. After this interval 1 CC. of the sodium chloride solution was added, shaken thoroughly, and allowed to stand 2 minutes before observations were made. By means of intermediate dilutions the maximum amount of the gelatin which just failed to protect the gold hydrosol from precipitation was readily determined. The value of this amount expressed in milligrams is the gold number of the sample of gelatin. Great care was taken to have all glassware absolutely clean, as there was only a very slight difference between the gold numbers of widely different samples of gelatin. Preparation of Gelatin Dispersions for Jelly Strength Determinations Seven-gram samples of gelatin were weighed out and placed in glass containers which had the following speci-
J. P h y r . Chem., 29, 792 (1925). J. D u i v y Sci.. 8, 500 (1925).
Zsigmondy-Spear, “Chemistry of Colloids,” p. 106, John Wiley & Sons, I n c , 1917.
URIKG recent years numerous investiqations have been carried out on the physical and chemical characteristics of gelatin. From the standpoint of the manufacturer and the consumer the important characteristics of gelatin are jelly strength, riscosity, hydrogen-ion concentration, ash content, protective power, color, clarity, odor, and purity. Since the ice cream trade has required the manufacturer to make a smoother product, the practice of adding gelatin or some other protective colloidal dispersion to the ice cream mix has become universal throughout the industry. The authors realize that the determination of the gold number and the hydrogen-ion concentration is impracticable for the majority of ice cream manufacturers, but the determination of jelly strength is practicable because it can be carried out very successfully by the non-technical worker. The object of this investigation, therefore, was to ascertain whether or not any relationship exists between the jelly strength, the gold number, and the hydrogen-ion concentration of various commercial gelatins used in the manufacture of ice cream. Elliot and Sheppard2 found very little difference in the protective action of seventeen different gelatins of all grades and methods of manufacture. They also found that any classification of gelatins according to their gold numbers was too rough and did not bear any simple relation to the properties of chief interest to the users of gelatins. Tartar and Lorak3 found that between p H values of 8 and 5 the hydrogen-ion concentration had practically no influence on the protective action; below a p H of approximately 4.7, the protective action decreased very rapidly with increase of hydrogen-ion concentration. Some time after the beginning of the present investigation, Moore, Combs, and Dahle4 published their results, from which they concluded that there was no direct relationship between gold numbers, hydrogen-ion concentration, and jelly strength. They used six different gelatins. Samples of commercial gelatins were obtained from nine of the leading gelatin manufacturers, and their high-, medium-, and low-grade gelatins were selected for this investigation. Preparation of Gold Sol
For the determination of the gold number, Zsigmondy’s red sol was prepared in the following manner: 120 cc. of re-
’ Received 3
4
January 27, 1927.
I S D U S T R I A L AA4TD ENGINEERI,VG CHEMISTRY
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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).
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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.
