April, 1926
I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
383
erize cyclopentadiene, but BiC13 does. The trichloride high molecular weight polymers which are white, amorphous powders insoluble in alcohol. of vanadium has no effect. I n Group VI the chlorides of sulfur and selenium as well Isoprene and the butadiene homologs are also converted as thionyl and sulfuryl chloride react very energetically with by means of tin tetrachloride into new hydrocarbons of high cyclopentadiene, apparently polymerizing and then adding molecular weight, which are different from those obtained by on to the polymerization product. heating or by the sodium method. None of the halides of the Group VI1 elements polymerized If cyclopentadiene were cheap-at present it costs about cyclopentadiene. eighty dollars per pound-its polymerization product might I n Group VI11 only FeC13 and FeBra worked. FeC12, find some practical uses as a lacquer, not as a rubber. FeF3, as well as CoClz and NiC12, were inactive. A benzene solution of cyclopentadiene rubber when allowed The organic acid halides, such as acetyl chloride, acetyl to evaporate deposits a resinous film which absorbs oxygen bromide, oxalylchloride, etc., had no polymerizing effect. and forms a hard, glassy, absolutely insoluble finish. The field is quite large for further work of this kind, Other Possibilities especially as the crude amylenes resulting from the cracking ,hot only does tin tetrachloride polymerize cyclopentadiene, of petroleum oils can probably be converted into solid resins but also indene, styrene, and phenylbutadiene, to give new by means of these catalysts.
Further Studies of Quinone Tannag
elsz
By Arthur W. Thomas and Margaret W. Kelly COLT-MBIA
I
UNIVERSITY. NEWY O R K , N. Y.
N COSTINUATION of the authors’ investigations of ing light upon the influence of such salts upon the tanning the tanning effect of benzoquinone, further information action of vegetable extracts in alkaline solutions. is submitted in this paper concerning this tanning agent, Effect of Sodium Chloride dealing with the effect of simple salts, the behavior of quinonetanned leather in contact with alcohol and tannic acid tanSince quinone solutions cannot be electrometrically tinage of quinone leather. trated by means of the hydrogen electrode, the pH of the The previously published paper3 showed that quinone solutions was fixed by means of buffer solutions.’ I n view tans hide substance only in of previous results in quinone tannage,3 pH values alkaline solutions. Since of 7 , 9, and 11 were chosen p u r e g a l l o t n n n i n (tannic The addition of sodium chloride retards the rate of acid) has been shown to upon which to superimpose quinone tanning in alkaline solutions. In neutral tan only in acid solution^,^ the effect of added salt. A solutions, although sodium chloride retards the the tanning action of commixture of M/l5 Na2HP04 tanning, sodium sulfate aids it. Alcohol extraction of mercial vegetable tanning and M / l 5 KHzPO?was used quinone leathers removes considerable amounts of extracts shown in alkaline for pH = 7 , M / l 5 Na2HP04 fixed “tannin,” more from undried than from dried for pH = 9, and M/15 Naz solutions was suggested to leathers, and more as the initial tannage is more be due to the presence of HPOd plus M/10 NaOH for alkaline, just as i n the case of vegetable-tanned pH = 11. All were adbodies of quinone nature.6 leathers. Quinone leather combines with very little The shapes of the curves justed e l e c t r om e t r i c a l l y gallotannin. wherein rate of tanning was with the hydrogen electrode. plotted as a function of the Pure quinone, 2.74 grams UHof the tanning solutions in weight. was ulaced in bffered striking eiidence in support of this suggestion. each of a series of 400-cc. bottles contaikng 200-ci. portions A study of the action of salts upon the rate of fixation of buffer solution. Weighed portions of pure sodium chloride of vegetable tannins by hide substance6 has shown that were then added to each to give the desired molarities noted sodium chloride and sulfate inhibit the tannage on the acid in Table I, following which, portions of defatted hide powder and alkaline sides of the isoelectric point of collagen, the equal to 2.000 grams of absolutely dry substance were latter being more effective than the former. This effect added. The bottles were rotated at room temperature is to be expected in tanning solutions on the acid side of for 24 hours, and the contents were then filtered quantitathe isoelectric point of collagen in view of the Procter-Wilson tively in Wilson-Kern extractors. When the samples were theory of vegetable tanning. The mechanism of the effect completely washed, as shown by negative tests for quinone in alkaline solutions is not so readily amenable to expla- and sodium chloride, they were air-dried, followed by drying nation, however. in vacuo a t 100’ C. The increase in weight of the tanned Experiments involving the effects of neutral salts upon samples was calculated as “tannin fixed.” The weight of quinone tannage have been planned with the view of throw- 2.74 grams of quinone was selected since this amount forins a saturated solution in 200 cc. of water. The results are 1 Presented before the Division of Leather and Gelatin Chemistry at the given in Table I. 6Sth Meeting of the American Chemical Society, Ithaca. N. Y., September Exclusive of the p H = 9 values, which are doubtful owing 8 to 13, 1924. Received October 30, 1925. 2 Contribution No. 498 from the Department of Chemistry, Columbia to filtration difficulties, it is seen that sodium chloride deUniversity. creases the rate of tanning. 8 Thomas and Kelly, THISJOWRNAL, 16, 925 (1924). It is a well-known fact that sodium chloride increases I b i d . , 16, 800 (1924). the hydrogen-ion activity of acid solutions. Therefore, 6 I b i d , 16, 1148 (1923). it appeared probable that the decrease in the rate of tanning e l b i d . , 15 1262 (1923).
INDUSTRIALAND ENGINEERING CHEMISTRY
384
might be ascribed to this effect upon the alkaline solutionsnamely, t o an increase in hydrogen-ion activity or diminished pH. To ascertain whether the amounts of sodium chloride employed might have affected the pH values of the buffer solutions, varying amounts of sodium chloride were added to the pH = 7 phosphate bdffer solution and the pHvalues then determined by means of the hydrogen electrode. The effects were as follows: no NaC1, p H = 7.04; 0.5 M NaC1, pH = 6.68; 1 M NaC1, p H = 6.47; and 2 M NaCl, pH = 6.19. Table I-Effect
of S o d i u m Chlorlde u p o n Quinone Tannage Grams
Molarity of NaCl present
NO.
“tannin fixed” b y 2 grams hide substance
PH 1 7.04 0 0.509 2 7.04 0.429 0.5 3 1 7.04 0.332 4 7.04 0.204 2 5 8.99 0.586 0 6 8.99 0.602’ 0.5 7 8.99 1 0.588’ 8 8.99 2 0 . 489’ 0.622 9 10.96 0 10 10.96 0.648 0.5 11 10.96 1 0.523 12 2 10.96 0.448 a These specimens clogged the filters resulting in an extremely slow rate of filtration which is paramount to a 1ong)er period of tannage. Hence these figures are too large.
Vol. 18, No. 4
tions of quinone. The pH of these solutions was undoubtedly slightly more acid than pH = 5.7, the pH of ordinary laboratory distilled water. The results are given in Table 111. The technic was identical with that described in connection with the data in Tables I and 11, except for the absence of buffer salts. A plus (+) sign means positive gain in weight of the hide powder whereas a minus (-) sign signifies a loss in weight. of Salts u p o n Quinone Tannage in Distilled Water Grams “tannin fixed” Molarity of by 2 grams CHARACTER OF TANNED No. salt present hide substance POWDERS 1 0 2 0.5 M NaCl 3 1 -0.013 Dark brown; harsh 4 2 -0.014 5 0 $0.004 6 0.5M NazSOc +0.008 Dark brown; softer 7 1 +0.033 Dark brown; well tanned 8 1.5 +O. 048 Dark brown; very well tanned a The duplication of results is,possible to. *5 mg. The temperature of tanning was room temperature in all experiments. Table 111-Effect
+::8”1
1
These data show a striking contrast between the effects of sodium chloride and sulfate. The latter definitely promotes quinone tannage in pure water solution, resulting in the formation of a well-tanned leather as far as can be judged from hide powder results.
Addition of salt sufficient to render the pH = 10.96 buffer Alcoholic Extraction of Quinone Leather solution 2 molar with respect to sodium chloride reduced the p H to 9.95. I n previous experiments with the extraction of vegetableIt was apparent from these measurements that whether or not the effect of the salt was actually exerted upon the tanned leathers7 it was found that when leathers that had tannage or just upon been tanned in alkaline solutions were extracted with hot a change in pH was alcohol there was an increase in the weight of the leather open t o q u e s t i o n . although tannin was a t the same time removed by alcohol. The salt was, there- This paradoxical situation was suggested to be due to the fore, dissolved in the oxidation of ethyl alcohol to aldehyde and to the fixation buffer s o l u t i o n a n d of the latter by the leather. Quinone-tanned leathers should then retitrated with do the same thing. Portions of defatted hide powder equal to 1.000 gram of buffer to reestablish absolutelv drv substance were tanned in 100-cc. Dortions t h e desired pH, whereupon the qui- of phosphate buffer solutions containing 1.37 grams quinone none was added. fol- by rotating in 400-cc. bottles a t room temperature for 24 lowed bv the ’hide , hours. They were then washed with distilled water in powder. ?he tannage Wilson-Kern extractors. The tannages a t each p H were was carried out as done in duplicate. One set of these duplicates (a series) was dried in vacuo a t 100” C., in order to measure the amounts Fi$ure 1-Effect of S o d i u m Chloride before and the u p o n Quinone Tannage a t p H of 7.0 are showninTable 11 of “tannin” fixed. These were then extracted with alcohol a n d 11.0 and in Figure 1. Ex- as examples of the alcoholic extraction of dried quinone periments a t pH = 9 were omitted on account of the previous leathers. The other set of duplicates (b series) was taken while wet from the extractors and submitted directly to unsatisfactory experience. alcoholic extraction as examples of alcoholic extraction of Table 11-Effect of S o d i u m Chloride u p o n Quinone Tannage undried leathers. This was done since marked differences C.rams in the stability of raw and desiccated leathers to alcoholic “tannin fixed” Molarity of by 2 grams extraction have been shown previously.’ DH NaCl present hide substance No. Y
1 2 3 4 5 6 7
7.04 6.98 6.95 6.96 10.96 11.02
8
10.96
11.01
0 0.5 1 2 0
0.5 1 2
0.503 0.527 0.488 0.376 0.602 0.598 0.557 0.452
These results remove all doubt concerning the influence of sodium chloride upon quinone tannage. It progressively decreases the rate of tannage with increase in its concentration at pH = 11, and likewise at pH = 7, except in low concentration, where it increases the rate slightly. This latter effect is similar to the action of sodium chloride upon gambier and hemlock bark tannagese at pH = 5 . The fact that sodium chloride may act directly upon the hide powder as a catalyst for hydrolysis previous to tanning by quinone .is shown in experiments wherein this salt and sodium sulfate were added to distilled water tanning solu-
Y
Table IV-Alcoholic Extraction of Quinone Leathers Grams “tannin REMOVED pH of fixed” by 1 P E R CENT OF FIXEDTANNIN tanning gram hide From wet KO. soln. substance leathers From dried leathers la lb
2a 2b 3a 3b
4a 46 5a 5b X Y
7 7 8
0.33i
8
9 9 10 10
X
Y
43
29
36
28
32
29
32
24
0.279 0.339
0.iii
11 0.iii 11 21 15 = from weight of extracted material. = from weight of dried extracted leathers.
...
X 11 9.1 7.5 6.2 6.0
Y 4.1 (gain) 5.5 (gain) 8.9 (gain) 7.9 (gain) 11
(gain)
The alcoholic extractions, in which the extracted specimen was submitted to the hot vapors as well as to liquid alcohol, 7
THISJOURNAL, 16, 31 (1924).
INDUSTRIAL A N D ENGINEERING CHEMISTRY
April, 1926
were continued until no more material appeared to be removed from the samples, as evidenced by the color of the extract. This required 493 hours total extraction time for the ram leathers and 128 hours for the dried samples. The results are summarized in Table IV. It should be carefully noted that all percentages are calculated on the amounts of tannin fixed by the hide substance and not on the basis of the leathers. The results shown in Table IV agree with those found Tvith hemlock bark and gambier leathers; namely, as the amounts of tannin removed are compared with the pH values of the tanning solutions in which the leathers were made, it is found that alkaline tanned leathers are more resistant to alcoholic treatment as the pH value of tannage is greater. Also, where the percentages of extracted material determined from the weight of extract and from loss in weight of the leather are compared, i t is seen that simultaneously with the removal of fixed tannin something else is being fixed by the leather. This must be acetaldehyde. It would appear that part of the mechanism of alcoholic extraction of alkaline tanned leathers is the reduction of fixed tannin in the leather, which upon being reduced is no longer a tannin and is washed out by alcohol. Hydroquinone has no tanning properties. Hence if the quinone in combination with the hide protein is reduced, i t will be promptly removed by the alcohol and the aldehyde formed will combine with the protein. The presence of air also aids in this oxidation. This mechanism is more strikingly shown in the data for the alcoholic extraction of the dried leathers, which incidentally are more stable toward alcohol than the moist raw leathers, just as has been found for gambier and hemlock leathers. Vegetable Retannage of Quinone Leather
Table V-Gallotannin Fixation b y Quinone Leather Change in weight Change in weight of quinone leather pH of of quinone leather Gram solution Gram + O 068 7 + O . 117 +0.053 8 +0.178 +0.069 9 -0.175 +0.070 10 - 0.554 +0.095 11 -0.638 12 -0.814 +0.089
p ~ o f 1
2
3 4 5
The data show in the pH range of 1 to 8 that the general trend of rate of tannin fixation as a function of pH is masked by the quinone tannage and that very little gallotannin is fixed by quinone leather-i. e., the experimental results support the chemical theories of gallotannin and of quinone tannages. The loss of weight on the alkaline side of pH 8 was not expected. While quinone tannage was known to be slightly reversible-i. e., "quinone tannin" is always found in traces when quinone leather is treated with distilled water-the large losses in the alkaline gallotannin solutions pointed to the necessity for the following experiment. Portions of quinone-tanned hide powder equal to 1.426 grams dry'basis were agitated with 100-cc. portions of buffer solutions for 24 hours, filtered and washed with distilled water in Wilson-Kern extractors, dried in vacuo at 100" C., and weighed. The results given in Table VI and Figure 2 showed the marked reversibility of this quinone leather in alkaline solutions, thus accounting for the losses in the alkaline gallotannin solutions. Table VI-Aqueous pH of buffer solution 2 3 4 5
e /
Since quinone combines with amino groups after oxidation of the same, according to Meunier's theory, and vegetable tannins combine with the same groups, quinone leather should not show any marked fixative capacity for gallotannin.
385
7.5 8 9
10 11 12
Extraction of Quinone Leather -LOSS
Gram 0.029 0.027 0.033
IN WBIGHT-
0.037
0.040 0.056
0.077 0.080 0.088 0.098 0.185
0.374
Per cent 2.0 2.0
2.3 2.6 2.8
3.9 5.4
5.6 6.2 6.9 13.0 26.2
I n Figure 2 the rate of gallotannin tannage of hide powder is included for comparison with the curve for tannage of quinone leather. It is apparent that quinone tannage takes place a t the same groups of the collagen molecule as vegetable tannage. Acknowledgment
The authors are indebted to A. F. Gallun and Sons Company for grants in aid of this investigation.
Calendar of Meetings
p n Figure 2-Aqueous
of soLuriow Extraction of Q u i n o n e Leather
Portions of quinone-tanned hide powder weighing 3.985 grams (equal to 3.566 grams dry basis and containing exactly 2.000 grams hide substance) were subjected to the tanning action of 100-cc. portions of tannic acid solution (4 grams tannic acid per 100 cc.) a t various p H values for 24 hours. The mixtures were filtered and washed in Wilson-Kern extractors, dried completely in vacuo at 100" C., and weighed. The quinone leather used had been made by 10 days' tannage in a saturated quinone solution a t p H 10.5. The results are submitted in Table V and in Figure 2.
American Chemical Society-7lst Meeting, Tulsa, Okla., April 5 to 9, 1926. 72nd Meeting, Philadelphia, Pa., September 3 t o 8, 1926. 73rd Meeting, Richmond, Va., April 12 to 16, 1927. American Electrochemical Society-Spring Meeting, Chicago Beach Hotel, Chicago, Ill., April 22 to 24, 1926. Fall Meeting, Washington, D. C., October 7 to 9, 1926. Association of Chemical Equipment Manufacturers-2nd Chemical Equipment Exposition, Cleveland, Ohio, May 10 to 15, 1926. American Leather Chemists Association-23rd Annual Convention, Traymore Hotel, Atlantic City, N. fl., June 2 to 4, 1926. American Institute of Chemical Engineers-Berlin, N. H., June 21 to 23, 1926. Fourth Annual Colloid Symposium-Massachusetts Institute of Technology, Cambridge, Mass., June 23 to 25, 1926.
