June, 1925
I-VD USTRIAL AND ENGINEERI-VG CHEMISTRY
583
type of curves for chrome exchange, as a function of the demonstrating the justification of extending the ionic concept concentration of the liquors, with maxima in the vicinity to reactions of proteins. of 15 grams Crz03 per liter. The extremely basic liquors Bibliography were also investigated, but the results are omitted on account 1-Davison, J . Phrs. Chem., 21, 190 (1917). of inaccuracies in data caused by the instability of these 2-Griliches, Collegium, Nos. 605-606, 416, 471 (1920) ; compare also liquors as acid is removed by the permutite. They indicated Stiasny, Ibid., No. 606, 479 (1920). Wilson and Kern, THISJOURNAL, la, 465 (1920); ( b ) Thomas, the same type of curves, however. As permutite only J . A m3-(a) . Leafher Chem. iissoc., 18, 423 (1923); (c) Wilson, “The Chemistry of reacts with cations, these curves illustrate the mechanism Leather Manufacture,” A. C. S. Monograph, The Chemical Catalog Co., of reactions for electropositive chromium. d study of the New York, 1923. 4-(a) Baldwin, J . A m . Leafher Chem. Assoc., 14,433 (1919); (b) Thomas per cent basicity of the chrome complex, given for the 37 per cent basic liquor, reveals a steady increase in acidity and Kelly, THISJOURNAL, 13,31 (1921); (c) Ibid., 14,621 (1922); ( d ) Thomas, J . A m . Leafher Chem. Assoc., 16, 423 (1923). up to the maximum exchange, but thereafter a decrease is 5 S c h o r l e m m e r , Collegium, No. 607, 536 (1920); J . A m . Leather Chem. noted, caused by the transference of sulfate complex into a ilssoc., 19, 574 (1924). G W i n k l e r , 2. angew. Chem., 26, 231 (1913); I b i d . , 27, 630 (1914); negatively charged complex, which does not take part in Scales and Harrison, THIS J O U R N A L , 12, 350 (1920). the reaction with permutite. ’?-Thomas, J . A m . Leafher Chem. Assoc., 15, 504 (1920). The amphoteric character of collagen will, however, make 8-Gustavson, Ibid., 19, 446 (1924). possible a coprecipitation of electropositive collagen and 9-Kubelka, Kohler, and Berka, Collegium, No, 663, 307 (1924), theoelectronegative chrome, and the difference in chrome fixation retical part. 10-Berzelius, Lehrbuch der Chemie, 9, 372 (1845). at higher concentration by permutite and collagen will be 11-Burton, J . Soc. Leather Trade Chem., 6, 183, 244 (1921); I b i d . , 6, explained. Electrophoresis experiments, using the stock 6 (1922). liquors, gave in all cases both anodic and cathodic migration, 12-Ref. 36, p. 308. 13-Werner, “Neuere Anschauungen auf dem Gebiete der anorganischen and particularly strong negative chrome migration occurred in the liquors with basicities around 35 to 40 per cent. The Chemie,” 1913, p. 336. F. Vieweg & Sohn, Braunschweig. 14-Procter and Law, J . SOC.Chem. I n d . , 26, 297 (1909). different shape in chrome fixation curves, with a sharp 15-Wilson, J . A m . Leather Chem. Assoc., la, 108 (1917). maximum in extremely basic liquors, may indicate that a t 16-Pauli in “Physics and Chemistry of Colloids,” edited by the Faravery high basicities the hydroxyl groups retard the formation day Society, 1921, p. 16. 17-Thomas and Foster, THIS JOURN.~L, 14, 132 (1922). of such complex or, more probably, that the low H-ion concentration was not favorable for the reaction. We must expect that increase in H-ion concentration to a certain limit would give the optimum for this reaction, and if this reasoning is true it explains the difference in chrome fixation. The formation of negative complexes or micelles in aluBy Louis Sattler minium salts has been investigated by Pauli.’G As the exK E N TCHEMICAL LABORATORIES, UNIVERSITY OF CHICAGO, CEIcAGo, I L L . istence of a chrome anion is a function of concentration, nature of acid radical associated with chromium, basicity, and neutral ISCHER2 describes a vacuum fractionator which has a salt content, and as there is little probability of its formation number of practical objections which the present form in dilute solution as found in tanning, any general theory eliminates, The two traps prevent the distillate from being of chrome tanning based thereupon has no experimental carried into the vacuum pump. In the older form there was basis. A secondary reaction taking place a t higher concen- considerable contamination of the fractions due to the accutration seems reasonable, and explains experimental facts hitherto not understood. Thomas and Foster17found that addition of sodium sulfate to a chrome liquor containing 100 grams Crz03per liter gave a minimum of chrome fixation by hide substance when the solution was unimolal in sodium sulfate. At lower concentrations of the chrome liquor no such point was observed. As the formation of a negative chromium complex will be facilitated by excess of neutral sulfate and also by increase in concentration of the chrome liquor, this trend of the curve may indicate a secondary reaction between positively charged protein and negatively charged chrome anion. A minimum H-ion concentration is further reached in about molal concentration of sodium sulfate, which will compensate any retardation caused by decrease in the actual acidity by addition of neutral sulfate. The behavior of very concentrated chrome liquors in regard to chrome fixation further points t o such a dual nature of the chrome tanning process. Study of electrophoresis of these liquors a t several concentrations and further quantitative data, with establishment of the conditions that influence the formation of the chrome anion and the mechanism of the reaction between this com- mulation of drops of liquid between stopcocks 2 and 4,which plex and hide substance, are desirable before any final theory would drain back into the receiving flask. The reservoir can be advanced. above stopcock 2 is very convenient because the distillate collects there while the receiver is being changed, The coil Conclusion between stopcocks 2 and 4 serves to remove the strain from The data from this investigation cannot be based upon the the apparatus. Stopcocks 1 , 3 , and 4 are of 1-mm. bore, while concept of the combination of chrome and hide substance stopcock 2 is 3 mm. as being an adsorption only involving physical forces, but 1 Received February 21, 192.3 form, instead, an additional link in the chain of evidence 3 Bey., 35, 2160 (1902).
An Improved Fischer Vacuum Fractionator’
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