84
INDUSTRIAL AND ENGINEERING CHEMISTRY
purification of the gas is almost impossible, or prohibitive in cost. The way has probably been opened for using these oils through two recent developments. The liquid purification process for removing hydrogen sulfide from gas, developed by the Koppers Company, has been perfected by the Pacific Gas & Electric Company, so that, instead of releasing the hydrogen sulfide into the air from the solution, it is now possible to recover all of the sulfur in a high state of purity and in a form in which it may have some valuable uses. The organic sulfur, which also increases with an increase in the sulfur content of the oil, and which, in quantities of over 30 grains per 100 cubic feet, becomes highly objectionable, is successfully reduced in quantity with the oil-washing process used in Portland. Since the cost of the oil is such a large part of the manufacturing cost, i t is not possible to make any radical change in the situation by improvements in plant processes or increased efficiency of operation. However, these have not been neglected, and the companies are spending money freely for research work. One of the companies has made improvements in spraying oil into a generator; another has carried on tests on a continuous process for gas-making; another is experimenting with the use of silicon carbide, fused spinel, and other brick having special properties of value for checker brick in a gas generator. Search for New Gas-Making Materials
Prolonging the life of a process by various expedients, which at the time of their adoption are recognized to be but of short duration, is far from satisfactory, and the gas utilities are taking measures to find a gas-making material that will be more permanent in supply and stable in price than fuel oil. In the southern part of the state a considerable quantity of natural gas is now supplied to the industries during the off-peak periods in competition with oil. A gradual restriction in the industrial use of the natural gas supplemented, as now, with oil gas during peak periods will take care of the domestic requirements for some time, and no rapid change to another process may be necessary as in the northern part of the state where the companies will be more immediately affected. The status of our fuel situation would be serious if it were not for the fact that there are large quanti'ties of lignites and sub-bituminous coals in the northern part of the state that may be available for gas-making. Treatment of the coal and special gas-making apparatus may be necessary, however. Other surrounding states and Alaska also have coals that may have to be considered. An investigation is already under way to determine the value of the coal resources of this and neighboring states for purposes of gas-making. An appropriation of $20,000 has been made to start the work, a technical staff has been organized, and laboratory facilities have been arranged. The cooperation of the U. S. Bureau of Mines has also been secured, and they have assigned a n engineer to work with the California utilities on this problem. Realizing fully that important changes must be made in our gas-making processes, the gas company executives are earnestly seeking means whereby the readjustments may be brought about with the least shock to their organizations and the least disturbance in the quality or cost of gas to their consumers.
Vol. 18, No. 1
Effect of Vegetable Tanning upon the Combination of Collagen with Acid' By John Arthur Wilson and Armond W. Bear A. F. GALLUN& SONSCo., MILWAUKEE, WIS.
A
CCORDING to the Procter-Wilson theory of vegetable
tanning12when the skin protein collagen is bathed in tan liquor, it first combines with hydrogen ion, becoming positively charged, and then neutralizes the negatively charged tannin molecules by combining with them, The resulting compound is very stable, being hydrolyzed only slightly, if at all, by continued w a ~ h i n g . ~This view of the mechanism of tanning suggests that the tannin attaches itself to those groups in the protein molecule which are capable of combining with hydrogen ion. Conversely, one would expect the capacity of the protein to combine with hydrogen ion to decrease as the amount of combined tannin increases. No practical way has yet been found for measuring the amount of acid combined with collagen in contact with a n acid solution of known strength, as has been done for gelatin, because collagen is insoluble and has a complicated, fibrous structure, and the acid distributes itself between three phases not easily separable for analysis: (1) the solid phase not in solution; (2) the solution absorbed by the protein jelly; and (3) the solution surrounding the jelly structure. It occurred to the writers, however, that i t would be valuable to know, even in a qualitative way, if the power of collagen to combine with hydrogen ion is really decreased by a n increasing degree of vegetable tannage. Fat-free hide powder was tanned in a solution of oak-bark extract for different lengths of time so as to producea series of powders of different degrees of tannage. The tanned powders were washed in running distilled water in WilsonKern extractors' until the wash water gave no color upon the addition of one drop of dilute ferric chloride solution. It was demonstrated that this washing was sufficient to remove any sulfuric acid previously added to the tanned powder, so that it may reasonably be assumed that all powders were free from combined acid. After washing, the powders were dried and analyzed for water and hide substance, the latter being taken as 5.62 times the per cent of nitrogen. The difference between 100 and the sum of these two values was taken as per cent of combined tannin. An amount of each tanned powder was taken containing exactly 1.000 gram of hide substance and put into a widemouth bottle. Over each was poured 50 cc. of 0.01 N sulfuric acid and the bottle was stoppered and shaken a t intervals for 24 hours to reach equilibrium. Then the hydrogen-ion concentration of the residual acid solution was determined by means of the hydrogen electrode. The results, shown in the table, indicate clearly that an increasing degree of vegetable tannage does lower the capacity of collagen to combine with acid. Combined tannin per 100 grams hide substance Grams None
6.84 7.59 7.86
Table I Concentration of Combined tannin Concentration of per 100 grams acid solution acid solution hide substance at equilibrium at equilibrium PH Grams PH
3.39 3.37 3.23 3.14
10.45 12.17 12.61 14.24 17.47
Solution without tanned powder
Snia Viscosa Shares to Be +sued in America-The Snia Viscosa, of Turin, Italy, apparently plans to establish a n international business in artificial wool. To this end plants will be opened in t h e United States and England and a group of American bankers will soon offer for public subscription 600,000 American shares at $16 per share.
3.07 2.96 2.86 2.80 2.72 2.05
Presented by J. A. Wilson before the Division of Leather and Gelatin Chemistry at the 09th Meeting of the American Chemical Society, Baltimore, Md., April 6 to 10, 1925. 2 Procter and Wilson, J . Chcm. SOC.(London), 109, 1327 (1916). 8 Wilson and Kern, THIS JOURNAL, 11, 1149 (1920). 4 Ibid.. 13. 772 (1921). 1
'
