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THE JOURNAL OF INDUETRIAL AND ENGINEERING CHEMISTRY
tion values) of heavy naphthas, neutral oils, paraffin. J . A m . Chem. Soc., 21 (1899), 1084.
Mabery: Bromine values (Allen’s method) of crude oils. A m . Chem. J . , 18 (18961, 215; 19 (1897), 796; 8 1 (1904), 16; 82 (1904), 185; 86 (I906), 266.
Richardson: Bromine values (method not mentioned) of petroleum residues. Allen, “Commercial Organic Analysis,” 4th edition, 111, 93. Weger: Bromine values (titration with an aqueous solution of KBr and KBrOa) of lamp oils. Z . Petroleum, 2 (1906), 101.
Vol. 14, No. 4
Utz: Bromine values (same method as Weger) of lamp oils. Z . 6 t h Zeum, 2 (1906), 43. Graefe: Bromine values (same method as Weger) of lamp oils. Z . angew. Chem., 18 (1906), 1580. Routala: Bromine values (same method as Weger) of mixes of gasoline with amylene, etc. Chem. Zentr., 1912, 11, 638. Dean and Hill: Bromine values (McIlhiney) of gasolines. Bur Mines, Tech. Paper 181 (1917). Grun and Wirth: Z . angew. Chem., 88 (1920), 295.
Time and Concentration Factors in the Combination of Tannin with Hide Substance”a I-Gambier.
11-Quebracho
By Arthur W. Thomas3 and Margaret W. Kelly DEPARTMENT OF CHEMISTRY, COLUMBIA UNIVERSITY, NEWYORK, N . Y.
Despite the fact that oegetable tanning is the oldest tanning process known, there are no scieptific data concerning the mechanism of thefixation of tannins by hide protein, or the factors which greatly influence the rate and degree of combination. The data given in this paper constitute a beginning in the study of this reaction, and while in themselves they do not serve for interpretation of the mysteries of the complex reactions involved, it is hoped that affer a few years’ experimentation suficient information will be accumulated to clarify the reactions and aid us in a more intelligent control of vegetable tanning. It can be said that while mild gambier shows a smooth adsorption curve, astringent quebracho acts in a strik.ingly different manner, giving greater $xation of tannin and showing a sharp maximum followed by an abrupt decline. A oery decided difference in the action of iypically mild and astringent exfracts is manifested and the value of further study to establish ihe reasons therefor is quite apparent.
The analysis consisted in the determination of moisture, protein (N X 5.614), fat (matter extracted by chloroform), and ash. The sum of the percentages of these constituents subtracted from 100 gave the per cent of tannin according to the definition of Wilson and Kern,4 that tannin is that portion of the water-soluble matter of certain vegetable materials which will precipitate gelatin from solution and which will form compounds with hide fiber which are resistant to washing. The resistance of the protein-tannin compound to washing has been demonstrated by the same authorsa6 DELICACYOF FERRIC CHLORIDETEST The writers considered all nontannin removed when 25 cc. of t,he washings gave no appreciable change of color upon addition of 3 drops of molar ferric chloride solution. The delicacy of this test as applied to solutions of gallic acid and pyrogallol is shown below. COLOR Calli6 Acid 1,000 Greenish black 10,000 Dark greenish yellow 50,000 Greenish yellow 75,000 Faint greenish 100,000 Yellow, as obtained with water
WO commonly used vegetable tans, gambier and quebracho, were selected for examination: gambier on account of its mild action and quebracho on account of its very astringent nature. The fixation of the tannins of these substances through a range of concentration up to saturated solutions and for the intervals of 6 hrs., 72 hrs., and 2 wks. has been measured.
T
1 Part in
Pyrogallol 1,000 Dark brown 20000 Brown 50’000 Slight brown tint 75:OOO Slightly brownish yellow 100,OOQ Very slight deepening of yellow color of blank
GENERALMETHOD Portions of hide powder equal to 10 g. of the absolutely dry material were placed in 400-cc. rubber-stoppered bottles. Six different concentrations of tan solution were poured on the hide powder specimens and the bottles rotated in a tumbling machine for the desired times, at the ends of which the contents mere filtered through muslin bags. The filtrates were saved for gelatin-salt test and the tanned hide powder was washed with running water and transferred back to the bottle, covered with 300 cc. of water, tumbled for 0 . 5 hr., and filtered again. This washing operation was repeated until the filtrate no longer showed a dark color upon addition of a few drops of ferric chloride solution. When the filtrate showed no nontannins present, by means of the ferric chloride test, the washed tanned powder was squeesed out, dried on flat dishes in a current of warm air, and bottled to await analysis. Presented before the Division of Leather Chemistry at the 62nd Meeting of the American Chemical Society, New Yark, N. Y.,September 6 to 10, 1921. * Contribution No. 384 from the Chemical Laboratories of Columbia University. 8 Assistant Professor.
It is evident that this ferric chloride test is delicate to 1 part in 75,000. Consequently there was not more t h h this amount of nontannin present in the last washings of the tanned powders, if gallic acid and pyrogallol are considered typical examples of nontannins. TESTSON GAMBIER SIX-HOUR ADSORPTION-FrOm a gambier paste containing 39.2 per cent of total solids (as determined by A. L. C. A. method), a stock solution was prepared by dissolving 1000 g. in water at 85” C., cooling, and adjusting approximately to 2 liters. It was atered through cheesecloth to remove coarse debris. From this stock solution the various dilutions were prepared. Approximate Concentration Grams Moist Gambier Total Solids per Liter Grams per Liter (Exact)
SOLUTION
1 2
3 4
1
5
6
25 60
100 200 350
600
THISJOURNAL, 12 (1920), 465. 6 Ibid., 12 (1920), 1149. 4
9.8 23.5 39.2 78.4 137.2 196.0
T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
April, 1922
Volumes of 200 cc. each of the above solutions were placed on portions of 1920 hide powder, equal to 10 g. of absolutely dry powder and rotated at room temperature for 6 hrs. FILTRATE No. Gelatin-&& Test No. of Washings
Practically +++ +
1 2 3 4 5 6
9 12 30 61 41 41
293
sufficient tannin present to form the insoluble, imputrescible, protein-tannin chemical compound. Approximate Concentration Total Solids FILTRATE Grams Moist Grams per Liter Gelatin-Salt No. of SOLUTIONGambier per Liter (Exact) Test Washinas 9.15 1 1 25 2 60 21.96 ill 3 100 36.6 Slight 43 53 4 200 73.2 53 5 350 128.1 53 6 500 183.0 1 Badly decomposed and hence discarded. 2 Slight decomposition.
-- +
I n the column headed “NO. of Washings” are indicated the number of times the samples were washed to get a nega35,
+++
Analytical data for this series of experiments are recorded in Table 111. TABLE 111-COMPOSITION AFTER 2-WK. ADSORPTION
......................... 2 Per cent water.. ................. 18.84 Fat ............................. 0.25 SAMPLE
............................. ......................... ................. ......
Ash Protein Tannin (by diff.) G. tannin per 100 g. protein..
0.24 75.31 5.36 7.12
3 4 16.28 17.16 0.15 0.30 0.60 0.66 76.09 71.93 6.88 9.95 9.04 13.83
5 16.37 0.20 0.53 72.32 10.58 14.63
6 16.45 0.18 0.59 69.71 13.07 18.75
TESTSON QUEBRACHO SIX-HOUR ADSORPTION-A stock solution was prepared by dissolving 150 g. of dry quebracho extract at 85” C., cooling, and making up to about 1500 cc. with distilled water. The total solid content of the dry extract was 80.5 per cent. Six solutions were made as noted below, and weights of hide powder equal to 10 g. absolutely dry substance plus 200 cc. Of the solutions were placed in bottles and rotated, etc., as previously described.
3 “0
8
26
50
I00
75
I25
GRAMSTOTALSOLIDS PER LITER
150 I75 OF SOLUTION
200
--
FIG.1
tive ferric chloride test. Under the heading “GelatinSalt Test,” it is seen that all the tannin present in solutions No. 1 and No. 2 was removed by the hide powder. The analytical data are given in Table I and plotted in Fig. 1. TABLE I-COMPOSITION SAMPLE 1 Per cent water. ........... 14.37
................. Fat ...................... Ash.. .................... Protein .................. Tannin (by diff.). . . . . . . . . . G. tannin per 100 g. protein.
...................
6-HR. ADSORPTION 2 3 4 5 6 13.86 10.75 15.33 14.25 14.04 0.65 0.72 0.57 0.40 0.80 0.67 0.16 0.15 0.22 0.30 0.21 0.26 83.66 80.30 83.01 79.33 79.76 80.06 1.16 4.97 5.45 4.64 4.98 4.97 1.39
AFTER
6.19
6.57
5.85
6.24
6.21
ADSORPTION-The filtrates from Samples 1 and 2 gave a negative gelatin-salt test, showing that all the tannin had been removed from solution by the hide protein. Filtrate 3 gave a slightly positive test, while all t.he rest were strongly positive. The number of washings required to remove all nontannins from the hide powders were: No. 1, 18; No. 2, 35; No. 3, 60; Nos. 4, 5, and 6, 66. Table I1 records the analytical data obt.ained. SEVENTY-TWO-HOUR
TABLE 11-COMPOSITIONAFTER 72-HR. ADSORPTION SAMPLE .................. 1 2 3 4 5 6 Per cent water ............ 9.70 11.16 12.01 10.65 10.48 10.20 Fat ...................... 0.71 0.68 0.47 0.38 0.43 0.30 Ash ...................... 0.22 0.21 Protein . . . . . . . . . . . . . . . . . . 87.61 83.17 1.76 4.78
Tannin (by diff.). . . . . . . . . . G. tannin per 100 g. protein ......................
2.01
5.75
0.24 0.29 0.24 81.29 81.92 81.97 5.99 6.76 6.88 7.37
8.25
8.39
Approximate Concentration Total Solids FILTRATE Grams Quebracho Grams per Liter Gelatin-Salt No. of SOLUTION Der Liter (Exact) Test Washines 6.3 5.07 11 17.0 13.7 11 35.0 28.1 44 50.0 40.2 44 75.0 60.3 44 80.4 100.0 44
0.27 82.24 6.99 8.50
TWO-WEEK ADSORPTIOK-NeW solutions of gambier were prepared as nearly as possible like the first described, and 1921 instead of 1920 hide powder was used. The definition that formation of leather is the conversion of hide substance to an insoluble imputrescible substance is illustrated here. I n Solutions 3 to 6, where an excess of tannin is shown by the gelatin-salt test, there was no decomposition as in the case of l and 2, where there was not
++ ++
It should be noted that Solutions 1 and 2 were completely detannized. The analytical results are listed in Table IV. TABLE IV-COMPOSITION AFTER 6-HR. ADSORPTION SAMPLE 1 2 3 4 5 6 Per cent water ............ 15.53 15.78 14.99 15.09 15.54 15 67 Fat ...................... 0.51 0.63 0.39 0.32 0.31 0 26
..................
Ash.
.................... .................
Protein Tannin (by diff.) ........ G. tannin per 100 g. protein
....................
0.22 0.25 0.29 0.24 80.50 72.88 68.92 70.84 3.24 10.46 15.41 13.51 4.03
14.35 22.36
19.07
0 25 0 25 72.86 75.12 11.04 9.70
15.15 12.91
A notable difference in the amount of tannin combined with the collagen at different concentrations of liquors is shown by this, and the 72-hr. and 2-wk. adsorptions, Inspection of Fig. 1 brings this out very strikingly. SEVENTY-TWO-HOUR ADSORPTION-The liquors were identical with those used in the 6-hr. experiment. FILTRATE Gelatin-Salt Test 1
2 3 4 5 6
-
++ + +
Slightly
No. of Washings 18 18 60 60 60 60
Solutions 1 and 2 were completely detannized, whereas Solution 3 showed but a trace of tannin left, in contradistinction to the 6-hr. experiment where a definite excess of tannin in the filtrate was noted. Table V contains the analytical data. TABLE V-COMPOSITION AFTER 72-HR. ADSORPTION SAMPLE 1 2 3 4 5 6 Per cent water.. . . . . . . . . . . 17.73 16.60 12.52 12.22 12.13 12.63 Fat. .................... 0 . 4 7 0.62 0.65 0.53 0.49 0.46 Ash ...................... 0.22 0.22 0.35 0.25 0.23 0.25 Protein. . . . . . . . . . . . . . . . . . 78.49 71.53 69.77 68.52 71.58 73.74 Tannin (by diff ,) . . . . . . . . . . 3.09 11.03 16.71 18.48 15.57 12.92
..............
G. tannin per 100 g . protein. . . . . . . . . . . . . . . . . . . .
3.94. 15.42 23.95
26.97
21.75
17.52
