January, 1927
IA'D USTRIAL A 9 D ENGINEERIXG CHESIISTR Y
would probably have unsuitable optical properties. The method is therefore offered as a general method for the determination of oils, using the word oil in its more restricted sense. Possible Application of Method
While the method has been devised for a particular purpose, and a definite type of determination, the fact that it makes use of only physical properties, those which are common to most oils, makes it a method capable of adaptation to a rather wide range of determinations. It should prove useful for the estimation of oils whenever the extraction of the oil is necessary, and when at the same time the volatility of the oil is sufficient to require consideration. An example would be the determination of fats in many kinds of food products. I n this case the method could be considerably simplified, and consequently shortened, since the concentration of the oil would usually be higher, and the volatility less pronounced, than in the case of flotation oil
81
emulsions. Compared to the standard fat determination used for food material (involving drying of the sample, extraction with dry ether, evaporation of the ether from the extract, and subsequent heating or drying to constant weight), such an optical method might offer distinct advantages. The length of time required for the analysis should be somewhat less than for the standard method. I n addition the loss of volatile oils, occasioned by drying of the sample and evaporation of the ether extract, would be largely avoided. For oils not soluble in alcohol, some preliminary experiments indicate that acetone may be satisfactorily substituted. Most of the fixed and volatile oils commonly found in food products which have been tested so far have been found readily soluble in acetone. However, the volatile oils, such as are found in spices, are usually readily soluble in alcohol, and i t is for such cases that this method should prove most useful. The possibilities offered by such an adaptation of the method are now under investigation in these laboratories.
Nature of One-Bath Chrome-Tanning Processes' By K. H. Gustavson WIDEN-LORD TANNINGCo., DANVERS,MASS.
T
HE basic sulfates and chlorides of chromium are the are kept intact. On the other hand, the anionic chromeprincipal tanning agents in the manufacture of chrome tanned hide protein must contain a smaller number of releather by the one-bath method. As a rule, these active basic groups. If this view is correct, however, the salts contain cationic chromium in the form of hydroxo- acidic groups have not been acted upon. To obtain addiacido-chromi complexes. Stiasny and others2 have shown tional information on this problem, the fixation of cationic that chromium compounds containing anionic chrome and anionic chromium by cationic chrome-tanned hide complexes also are fixed by the hide protein. protein and hide protein proper and the reverse reactions The mechanism of the fixation of the constituents of have been studied. chrome tanning agents by hide protein has not yet been Experimental Procedure adequately explained. The very complex nature of this t a n n a g e indicates that a Portions of hide powder number of factors, chemie q u i v a l e n t to 5 grams of cal and colloidal, are incollagen in sets of three were The mechanism of cationic chrome fixation by hide volved. The mechanism of tanned for 48 hours with powder is shown to differ from that of anionic chrome the cationic chromium fixasolutions of various chrofixation. Cationic chromium complexes probably react tion is best explained by the m i u m compounds. The by means of the acidic groups of the protein, with the chemical concept. Accordtreated specimens of hide formation of primary valency compounds. The fixation ing to Wilson13the principal powder were washed free of anionic chromium probably involves the formation process is the formation of a f r o m s o l u b l e chromium of molecular compounds by means of the basic protein primary valency compound salts and taken to dryness on groups. between the electropositive Biichner filters (70 to 72 per chrome complexes and the cent moisture). The total hide Drotein bv means of the weight was ascertained. A acidic protein groups. The mechanism of the anionic quantity of each sample equivalent to 1 gram of protein chrome fixation, however, cannot be explained upon this was kept. Thus a quantity equivalent to 4 grams of collagen basis. The occurrence of the maximum chrome fixation was used in the tanning series. Hide powder in portions of these compounds in the region of the isoelectric point equivalent to 4 grams of collagen was soaked in water for of hide protein is irreconcilable with the primary valency 12 hours and brought to about the same moisture content compound view. The formation of molecular compounds as the chrome-tanned specimens. All samples were then by means of the basic protein groups seems the most likely brought to the maximum total weight recorded by the explanation. According to this view, the two kinds of addition of water, and 200-cc. portions of the chrome solution chrome tannages would differ widely. The results of the were added. The tanning processes lasted 48 hours under investigation here reported support this assumption. continuous rotation. All comparative tests were conducted It would be expected that part of the acidic groups in the at the same time. This method was superior to that emhide protein in combination with cationic chromium are not ploying alcoholic dehydrated hide powder, as great difficulty available for further reactions, but that the basic groups was encountered in soaking such chrome-tanned stock back to a normal degree of hydration. After washing 1 Received August 18. 1926. * 2. a n g m . Chem., 37, 913 (1924); Collegium, 660, 190, 200 (1925); and drying, the samples were analyzed. The analytical 661, 270 (1925); 670, 41 (1926); J. A m . Leafher Chem. Assoc., 20, 383 procedure was the same as that described in a previous paper.' (1925); 21, 22 (1926). * J . A m . Leafher Chem. Assoc., 12, 108 (1917). Gustavson and Widen, THISJOURNAL, 17, 577 (1925).
INDUSTRIAL AND ENGINEERISG CHEMISTRY
82
Vol. 19, No. 1
Basic sulfates of chromium prepared from C.P. sodium uct had the following composition: Crz03, 7.33 per cent; bichromate and sulfuric acid were used to show the action collagen, 70.7 per cent; Cr203 on collagen basis, 10.37 per of cationic chromium. Oxalato and sulfito compounds cent. Table IV served as anionic chrome tanning agents. The stock solution 1 PRETASNED HIDE HIDE POWDER of sodium oxalato chromiate was brought to a final pH POWDER of 4.90 by adding alkali and then diluted to contain 8 grams T ox*- T 66cj, ACID T 6642 A C I D Crz03 per liter. The sulfito compound was prepared from LATO CHROMIC CHROMIC COLISULFATE SULFATE a 63 per cent acid chromic sulfate by the addition of sodium POUND (10.6 O./L. sulfite in a quantity to make the ratio of ?u'a2S03t o crpo3 CRaOs) CR203) Per cent Per cent Per c e n t as 3 to 1. The formation of anionic chromium is complete 8.12 7.41 4.21 7.17 under these conditions, according to Stiasny and S ~ e g o e . ~CraO3 Collagen SI.; 72.3 ii.2 69.0 ~~
CrzOa on collagen basis
Results
SERIES I-Hide powder tanned with a basic chromic sulfate was employed. The solution for this cationic pretannage had a concentration of 2.1 grams Cr& per liter and a n acidity of 66 per cent. Analysis of the pretanned stock gave the results shown in Table I. Table I Per cent 3.25 84.8 3.82 54.2
CrzOa Collagen CrzOa on collagen basis Acidity of chrome-collagen compound
This cationic tanned stock was treated with the anionic oxalato solution containing 8 grams Cr203 per liter and having a p H value of 4.90. Blanks with hide powder were run simultaneously. The results of t,his experiment are shown in Table 11. Table I1 CATIONICCHROME- REGULAR HIDE TANNED STOCK POWDER OXAOXALATO COMPOUND LATO COMPOUND Per cent Per cent
+
6.53 77.0 8.48 4.81
Crz03 Collagen CrzOa on collagen basis p H of filtrate
+
4.22 82.0 5.15 5.02
Assuming that the two processes involve different protein groups and thus are independent of each other, the theory 5.15, or 8.97 per cent Crz03 on collagen requires 3.82 basis, which corresponds with the value obtained, 8.48. The agreement is actually still better, because the pH of the pretanned stock solution is lower, corresponding to lower Cr203 figure of the stock from the experiment with the hide powder blank, as this change in pH occurs on the declining Crz03 curve. The decrease in pH is due chiefly to the displacement of sulfuric acid, held in combination with the basic protein groups, by the oxalato anions. SERIES11-Hide powder tanned with the chromic sulfate used in series I, but having a concentration of 5.2 grams Cr203per liter, was employed. Table I11 shows the composition of this cationic chrome-tanned stock.
+
Table 111 CrrOa Collagen
SO8 CnOs on collagen basis
Per cent 5.32 75.0 5.50 7.09
Table IV shows the results of this experiment. Independent anionic chrome fixation by the cationic 7.09, or 12.55 chrome-tanned hide powder requires 5.46 per cent Cr203 on collagen basis, against the value 11.36 per cent obtained. For the 66 per cent acid chromic sulfate, the theory requires 7.09 10.38, or 17.47 per cent CrzOa on collagen basis. Only 10.25 per cent was obtained, however. Hide powder tanned with the oxalato complex (anionic) was treated with this chromic sulfate. The resulting prod-
i
s Collegium, 670, 41 (1926).
... ...
5.46
10.38
4.98
...
...
...
+
Theoretically, 10.38 5.45, or 15.83 per cent Crp03 on collagen basis, is required. The value obtained was 10.37 per cent. SERIES 111-The pretanning basic sulfate liquor used in series 11, in a concentration of 10.6 grams Cr203 per liter, gave a tanned product containing 10.76 per cent Crz03 on collagen basis. After interaction with the oxalato compound it analyzed 15.14 per cent CrpOs on collagen basis. The pretanned stock treated with this sulfate liquor gave 12.04 per cent Crz03 on collagen basis. The theoretical value for an additive process in the oxalato compound was 15.79 per cent, against the 15.14 per cent Cr203 on collagen basis found. Under the same assumption, the basic sulfate figure should be 21.20 per cent, but only 12.04 per cent Cr203 on collagen basis was recorded. The oxalato pretanned hide powder gave with the same cationic sulfate liquor 10.37 per cent CrzOa on collagen basis, 15.41 per cent being required by theory. SERIESIV-Hide powder, containing chromium from a 45 per cent acid chromic sulfate solution in a concentration of 11.8 grams c1-203per liter, was studied next. The result,ng product had the composition given in Table V. This solution showed the presence of anodic chrome complexes. Table V Per cent 17.43 11.56 42.0
CrzOs on collagen basis SO3 on collagen basis Acidity of chrome-collagen compound
The results of this experiment are given in Table VI. Table VI STOCK
+
OXALATO
COXPOUND Per cent Cr203 on collagen basis SOa on collagen basis
STOCKC 63% ACID dHRoMic S X F A T E ( 2 7 . 6 G./L. CmO3) Per cent
20.96 2.09
17.53
...
I n the fixation of the oxalato compound, the theory re17.43, or 22.58 per cent Crz03 on collagen quires 5.15 basis, compared to 20.96 per cent found. For the 63 per cent acid chrome liquor follows a theoretical value of 13.35 17.43, or 30.78 per cent Cr203 on collagen basis. The amount obtained was 17.53 per cent.
+
+
Table VI1
+
+
10.25
11.36 0 . .52
+
STOCK ANIONIC SULFITO COMPOUND Per cent
CrzOs Collagen Total inorganic sulfur (as SOa) Combined sulfate (as SOa) CrzOn on collagen basis
16.49 63.1 12.49 5.56 26.13
+
STOCK CATIONIC CHROMIUM SULFATE ( 2 7 . 6 G./L. C R Z O ~ ) Per cent 9.65 76.1
...
12:68
SERIESV-Hide powder tanned with a 63 per cent acid chromic sulfate, showing 11.93 per cent CrzOa on collagen
83
January, 1927 basis, was treated with a sulfito compound having a concentration of 13.2 grams CrzOa, with entirely anodic migration. Tanning with a 63 per cent acid sulfate liquor containing 27.6 grams Ci-203 per liter was also conducted. The composition of the chrome retanned stock is given in Table VII. Examination of these liquors with regular hide powder gave the results in Table VIII.
the sulfito compound used in series 1'11. With the anionic sulfito compound it gave 17.02 per cent Cr& on collagen basis and with the anionic oxalato compound, 7.24 per cent, against 24.84 and 11.40 per cent for the sulfito and oxalato compounds, respectively. Discussion
The fixation of anionic complexes in the form of oxalato chromiate by hide powder tanned with cationic chromium Table VI11 (basic chromic sulfates) gives practically the same fixed HIDE POWDER HIDEPOWDER+ +ANIONIC 63% ACIDCHROMIC anionic chromium values as are obtained from the same SULFITO SULFATE solutions with regular hide powder. Probably, therefore, COMPOUND ( 2 7 . 6 G . / L . CRaOs) Per cent Per cent the cationic chrome tanning process does not involve the same protein groups as the anionic tannage. This difference CrzOs 13.09 8.98 Collagen 76.0 6S.4 is strikingly illustrated by the experiments in which 17.5 ... 9.60 Total inorganic sulfur (as SOa) 8.26 4.54 per cent of Crz03was incorporated by the use of an extremely Total sulfate (as sos) 11.82 Cr208 on collagen basis 19.14 basic chromic sulfate. Treating this highly tanned hide powder with cathodic basic sulfates leads to no additional The theory for sulfito compound requires 11.!33 4- 19.14, chrome fixation. On the other hand, the anionic compound, or 31.07 per cent CrlOz on collagen basis, against the 26.13 although possessing only about half the tanning capacity per cent found. The theory for cationic chromium sulfate of the cationic salt, shows nearly the same additional chrome requires 11.93 11.82, or 23.75 per cent Crz03 on collagen fixation as with regular hide powder. This retannage basis against the 12.68 per cent found. SERIESVI-A sulfito-tanned hide powder showing 19.6 with oxalato compounds reduces markedly the amount of sulfuric acid or combined sulfate held by the protein, probper cent Crz03on collagen basis, treated with a 63 per cent ably by means of its basic groups. The anionic complexes chromic sulfate in a concentration equal to 14 grams Cr203 and vegetable tannins react similarly, with hide powder, and per liter, which was fixed under the same experimental the fixation of tannins by cationic tanned stock is indeconditions by regular hide powder to 9.65 per cent Crz03 pendent of the degree of chrome tannage. Thomas and his on collagen basis, gave the figures shown in Table IX. collaborators6 proved that the basic protein groups participate in this type of tannage. A number of experimental Table IX Per cent findings substantiate the concept of the basic protein groups 13 19 as the vehicle in the formation of oxalato chromiate collagen 67 4 9 39 compounds. 7 89 19 57 The affinity of anionic chrome-tanned hide protein for cationic salts is much less than that of untreated hide protein. The fixation of cationic chromium by the anionic pretanned Such reactions, affecting the basic protein groups, seem t o hide powder, if an independent reaction, requires 19.60 inhibit the fixation of cationic chromium. This applies 9.65, or 29.25 per cent Crz03 on collagen basis. SERIESVII-A cationic chrome-tanned stock of high to deaminized hide powder and to the same powder tanned Cr203 content was prepared by treating hide powder with a with formaldehyde, tannins, and quinone. The fixation of basic chromic sulfate by hide protein 45 per cent acid chromic sulfate containing some anionic chromium, having 11.8 grams Cr& per liter. The com- comprises two separate, but mutually influenced, processesthe combination of cationic chromium by means of the acidic position of the pretanned stock is given in Table .X. protein groups and the combination of the hydrolyzed acid Table X by means of the basic protein groups. Chemical inactivation Per cent of basic protein groups reduces the acid-fixative capacity of Crz03 12.83 Collagen 73.6 the protein. The hydrolysis of the chromic salt is thereby SO3 7.98 repressed. Consequently the chrome fixation is decreased. Cr&s on collagen basis 17.43 Simultaneous structural rearrangements and redistributio'n The results of this experiment are given in Table XI. of valency forces induced by chemical interaction with the basic protein groups are possible factors. Table XI No strictly additive relationship in the quantities of STOCK -t CATIONIC STOCK ANIONIC 637, ACIDCHROMIC chromium in the cationic pretanned powders retanned with SULFITO SCLPATE ( 2 7 . 6 G /I,. C R ~ O ~ ) the sulfito compound is evident. Even in this case, however, COMPOUND Per cent Per cent the sulfito compounds have a greater affinity toward the CrzOa 17.92 12.13 cationic tanned hide powder than the cationic compounds. Collagen 61.7 139.2 These compounds, which contain both sulfito and sulfato CrtOa on collagen basis 29 04 17.53 Total inorganic sulfur (as SOs) 11 32 ... complexes and are colloidal, are so complicated that they Combined sulfate (as sod 5.45 7 X.. R are less suitable for the problem in question. I n a general The fixation of the anionic sulfito compound, if independent way, however, the data here given also support the view of the cationic chrome process, requires 17.43 19.10, or of the dual nature of the cationic and anionic chrome fixation. 36.53 per cent Crz03 on collagen basis, against the 29.04 Conclusion per cent found. For cationic chromic sulfate, under the same assumption, Cationic chromium combines with the acidic groups of the theory requires 17.43 11.82, or 29.25 per cent Cr203 the hide protein, forming a very stable salt. Anionic chroon collagen basis, against 17.53 per cent found. mium forms molecular compounds with the basic protein SERIESVIII-Stock pretanned with oxalato compound, groups. containing 5.70 per cent Cr20a on collagen basis, was treated 8 T H I S JOURNAL, 16, 1148 (1923); 16, 800, 925 (1924); J . Am. Chcm. with the oxalato compound used in the pretannage and with Soc., 48, 489 (1926).
+
+
+.
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