698
I-VDUSTRIAL A S D ENGINEERING CHEMISTRY
Table I-Fixation of W a t t l e T a n n i n i n Presence of Diverse Acids PHOF TANNIN PHOF TANHIN ADDEDTANNING FIXED BY ADDEDTANNING FIXED BY PRESENT ACID SOLUTION 2 SUBSTANCB GRAMSHIDE ~ & + ~
p&i&2:;-
6 Hrs. 24 Hrs. Grams Grams
Mols per liter
liler
ACETIC ACID
None 0.006 0.059 0.319 1.260 4.770
4.67 4.15 3.69 2.92 2.49 1.86
0.67 0.70 0.95 1.27 1.59 1.57
4.50 4.00 3.41 2.9s 2.44 1.96
0.58 0.66 0.80 1.12 1.29 1.66
0.82 0.90 1.39 1.56 1.93 1.80
h-one 4.77 0.0020b 4 . 2 4 0.0054b 3 . 5 7 0.013b 3.05 0.0430 2 . 4 8 0.1319 2 . 0 3
0.78 0.83 1.28 1.53 1.81 1.99
None 0.0022a 0.00480 0.00760 0.0133d 0.0222d
4.62 4.00 3.53 3.00 2.45 2.10
0.53 0.57 0.73 0.91 1.27 1.58
0.69 0.87 1.05 1.24 1.72 1.86
None 0.0025 0.0087a 0.017” 0.042b 0.127b
4.60 3.88 3.35 2.90 2.47
None 0.003a 0.007a
4.65 4.06 3.78 3.07 2,57 1.99
...
... ... .. ..
0.064a 0.254a
4.63 3.99 3.44 2.98 2.40 2.10
0.62 0.68 0.80 0.90 1.10 1.19
4.85 4.38 3.53 3.01 2.47 2.05
HYDROCHLORIC
0.73 0.87 1.23 1.48 1.74
CITRIC ACID
0.59 0.63 0.66 0.92 1.12 1.44
0.77 0.90 0.98 1.09 1.58 1.51 0.87 0.98 1.01 1.23 1.39 1.77
MONOCHLOROACETIC ACID
SUCCINIC ACID
None 0.008 0.031 0.09;.
0.62 0.63 0.88 0.96 1.26 1.37
OXALIC ACID
FORMIC ACID
Kone 0.004 0.013 0.031 0.166 0.425
24 Hrs. Grams
TARTARIC APTn .~~~ .~~~ ~.
LACTIC ACID
None 0.004b 0.013b 0.048b 0.092b 0.395b
6 Hrs. Grams
Mols per
0.86 1.03 1: il 1.57 1.71
. ,. ., .. ,
,.
..
0.65 0.70 0.85 1.17 1.40 1.61
ACID
None 4.85 0.59 0.71 0.0035 4 . 0 0 0.68 0.75 0.0075’ 3 . 2 3 0 70 0.93 0.0097a 2 . 9 1 0.90 1.04 0 . 0 1 4 ~ 2.41 1.24 1.21 0 . 0 2 4 ~ 1.90 1.22 1.48 Tanning solution was slightly turbid. b Tanning solution was decidedly turbid. c Tanning solution contained slight precipitate. d Tanning solution contained moderate amount of precipitate.
Vol. 21, No. 7
with the nature of the acids used. Taking the p~ range of 2.5 to 3.0, the order of tanning intensity is as given in Table 11, together ~ ~ with ~ the E strengths of the acids. Table 11-Order 6 - H o u ~TANNAGE
of Influence u p o n T a n n i n Fixation 2 4 - H o u ~TANNAGE
Acetic Lactic Formic Tartaric, citric Oxalic Hydrochloric
Acetic Lactjc Succinic Formic Citric Tartaric Oxalic Monochloroacetic Hydrochloric
INVERSBORDEROF ACIDSACCORDING TO DISSOCIATION CONSTANTS 1-Acetic 2-Succinic 3-Lactic 4-Formic 5-Citric &Tartaric. - -. .-.-
7-Monochloroacetic 8-Oxalic 9-Hydrochloric
Table I1 shows, within the limits of acids studied, that the order of tannin fixation a t a given pH value qualitatively is very closely inversely proportional t o the dissociation constants of the acids. Acknowledgment
The authors thank the A. F. Gallun & Sons Corporation, of Milwaukee, for grants in aid of this investigation. Literature Cited (1) I,oeb, “Proteins and the Theory of Colloidal Behavior,” McGraw-Hill Book Co.. New York. 1924. (2) Thomas and Foster, IND. ENG.CHEX.,15, 707 (1923). (3) Thomas and Kelly, Zbid., 15, 1148 (1923); 16, 800 (1924).
Syntan Tannage’s’ Arthur W. Thomas and Margaret W. Kelly DEPARTYENT O F CHEMISTRY, COLUMBIA UNIVERSITY, N E W YORK,N . Y.
HE name “syntans,” a contraction of the words “syn- as a function of the acidity conferred upon tan liquors by thetic tannins,,’ is applied to sulfonated aldehyde con- these strongly acid products has been found. It was theredensation products of hydroxyaromatic compounds fore considered timely t o start such an investigation. This which have tanning action, although chemically they do paper records data on the action of the combination of a synnot resemble the natural vegetable tannins. tan with each of two astringent vegetable extracts, queAs early as 1875 a product with tanning properties was bracho and wattle. The syntan used was an American prodprepared by Schiff (1)* by the action of phosphorus oxychloride uct known as “ L e ~ k a n o l . ’ ~ ~ Analysis of this syntan by the method recommended by upon phenolsulfonic acid, but the first process for the commercial manufacture of a syntan of technical value was Kohn, Breedis, and Crede ( 2 ) gave a total solids (corrected for introduced in 1912 by Stiasny. This product, known as alkali added in the determination) and an ash content of 361 Neradol, and other competing products of similar nature and 222 grams per liter, respectively. Concentrated stock solutions of wattIe and quebracho were extensively used in the Central Empires during the war owing to isolation from sources of vegetable tanning extracts. extracts were prepared by dissolving the dry extract in hot Syntans are not satisfactory tanning agents when used water and allowing t o stand overnight, after which the mixalone, one reason being their hydrolytic action on hide sub- tures were centrifuged and the supernatant liquid filtered by stance, but are claimed to be valuable adjuncts t o vegetable suction through filter paper. Total solids determinations tannins. Possessing lower molecular weight, they diffuse were made on these final solutions by the A. L. C. A. method. into the hide more rapidly than natural tannins. They Experimental Procedure have the property of rendering soluble the difficultly soluble components of certain vegetable tanning extracts and of Samples of defatted hide powder equivalent t o 2.000 grams, inhibiting mold growth. Syntans evert a bleaching action on vegetable-tanned leather and are used also for this reason. absolutely dry weight, were tanned in 200-cc. portions of Several general papers on the merits of the combination tanning solution for 24 hours unless otherwise indicated. of syntans with natural tannins in the production of leather Samples were then filtered in Wilson and Kern extractors and are in the literature, but as yet none comparing the effects washed for 24 hours with distilled water, when a negative test was always obtained for the various components of the 1 Presented b y A W Thomas before the Division of Leather and tanning solution employed. After air-drying, the tanned Gelatin Chemistry at the 74th Meeting of the American Chemical Society, samples were transferred t o weighing bottles and dried for Detroit, Mich , September 5 to 10, 1927 Received March 2, 1929 16 hours a t 100” C. in a vacuum oven. The increase in dry 2 Contribution from the Chemical Laboratories, Columbia University,
T
No. 601. Italic numbers in parenthesis refer to literature cited at end of article.
*
a Kindly furnished by the Rohm and Haas Company.
IXDUSTRIL4L A.VD E,VGIiVE’ERING C H E M I S T R Y
July, 1929 65
I
I
699
I
I
5 PERCENT S Y N T A N B Y VOLUME ..-*‘
I PERCENT SYNTAN BY V O L U M E
I5 PERCENT SYNTAN B Y VOLUME
Fiqure I
LO
a5
0 5
/O
J 5
20 0
5
20 0
15
10
Grams Quebracho Tofu1 Solids p e r 1 = Quebracho
5
L i f et-
-
In Figures 1 to 4, inclusive, the numbers on the curves are to be explained as follows: 4 Satural quebracho, untreated 2 = Quebracho H2SO4 3 = Quebracho HiSol xa?SO4
+ syntan
weight of samples was taken as a measure of tannin fixed from solution. In the preliminary adjustments of p H the hydrogen electrode was used in all cases except for solutions containing the syntan. Since the presence of the syntan interfered with the hydrogen electrode, the quinhydrone electrode was applied with satisfactory results. I n t h e experiments recorded in I I I I Tables I and I1 and Figures 1, 2, and 3, the results obtained from tannage with mixtures of (I) quebracho and varying amounts of Leukano1 (1, 5, 15, and 30 per cent of total volurnc: of tanning solution) are compared aith results from tannage by (2) quebracho titrated, with sulfuric acid, to pH values identical to those obtained by addition of Leuka n o l in (1); ( 3 ) 1 quebracho plus sodium sulfate, ti/O 20 30 40 . t r a t e d with sul‘urns Quebracho Gfu/ furic a c i d to pH So//’ds per L i f e r values identical to those obtained on addition of Leukanol; and (4)quebracho alone at its natural pH. The %.eights of sodium sulfate added in ( 3 ) were such as would be equivalent to the sodium sulfate occurring in Leukanol added to the corresponding quebracho-Leukanol mixtures. The sodium su1f:ite content of Leukanol was estimated from its ash content. Four concentrations of quebrarho, expressed on the total solids basis, as 2.5, 5.0, 10.0, and 20.0 grams total solids per liter. were chosen for the experiments. In most cases the pH of the final tanning filtrate, as well as of the original tanning solution, is recorded, and also the effect of the gelatin-salt test upon the filtrate. The character of tannage, as far as can be judged by appearance and “feel” of hide powder samples, is also included.
I
u
+
+
+
Table I-Fixation
of Quebracho Tannin in 24-Hour T a n n a g e f r o m S o l u t i o n s at Natural pH
PH
QUEBRACHO SOLIDS
Grams per liter 2.5
5.0
10.0 20.0
1
I
Beforea
After
4.6
1
TANNIN FIxEDb
CHARACTER OF TANNAGE
Grams
5.1
0,160.37-
4.7
0.58+ 0.52+
5.3
4.5 4.6 4.6
!
Poor Fair Good Good
“Before” refers to original tanning solution; “after” refers to solution removed from contact with hide powder at end of tanning intervd. b Signs refer to positive and negative gelatin-salt tests on filtrate. a
Although the addition of sulfuric acid and sodium sulfate to quebracho solutions engenders the formation of a finely divided precipitate, the authors feel that no considerable errors in results are hereby produced, as the tanned samples were filtered on the extractors through cambric cloth which permits free passage of this precipitated “sludge,” as estimated by blank determinations. Moreover, the tanned powders were rubbed thoroughly with a glass rod during the early part of the washing in the extractors to facilitate removal of the insolubles held on the surface of the tanned powders. However, no such precipitates formed in the wattle s o l u t i o n s 0.8 and therefore any doubt of the validity of the quebracho experiments should be 3 dispelled by the $i 06 results o b t a i n e d with wattle. Inordertostudy ‘? further the effect of change in con- $0.4 c e n t r a t i o n , conc e n t r a t e d solutions of quebrachoLeukanol and of fQ-R i $Qa z wattle- Leu k a n 01 were prepared in which the ratio of total solids of the U 0 yegetable extract 0 20 40 60 80 /OO to total solids of Grams N/att/e 7 0 h / Leukanol was 100 Soli’ds per L / f e r to 30. These stock 1 = Wattle + syntan solutions were di2 = Wattle + HsSO4 3 = Wattle + HzSOd + XaaSOd luted and 200-cc. 4 = Natural wattle, untreated
2
::
$3 s5 $
p
IhTDUXTRIAL AXD EXGINEERING CHEMISTRY
700
of Q u e b r a c h o - L e u k a n o l T a n n a g e w i t h T a n n a g e b y Q u e b r a c h o w i t h Added S u l f u r i c Acid, and Sulfuric Acid plus Sodium Sulfate
Tab:e 11-Comparison
1% LEUKANOLC
QUEBRACHO
SOLUTION
Added Total materiala solidsd
I;{
PH
Tannin
Before After
fixedb
2:
(1) (2) (3) (1) (2) (3) (1) (2) (3)
5% LEUKANOL
5.0 5.0 5.0 10.0 10.0 10.0 20.0 20.0 20.0
2.2 2.3 2.2 2.4 2.3 2.4 2.5 2.5 2.5 3.1 2.8 3.1
PH Before After
I
Grams 0.46g 0.18p 0.16~ 0.62g
3.3 2.9 3.3 3.8 3.1 3.7 3.6 3.4 3.7 3.8 3.7 4.0
1
24-HoU~T A N K A G E
24-HOUR T A X X A G E
G./L 2.5
(1)
VOl. 21, No. 7
1.8 1.8 1.8 1.8 1 . 8 1.8 1.8 1.8 1.8 1.9 1 . 9 1.9
0.40~
0,57f 0.87g 0.78g
0.66g 0.62g 0.86g 0.53g
1.9 1.8 2.2 1.9 2 . 2 2.0 2.0 2.0 2.1 2.2 2 . 4 2.0
T;;p
I 1
1
Grams I 0.55g 0.12p 0.19~ 0.73g 0.40~
0.5Pp 0.78g 0.63f 0.84g 0.9Og 1.12g
1 . 2 .7 ~.
I
15% LEUKANOL
24-HOUR
1
I
T,a;~p1 5 1 Tannin
n' ;T ;
pH Before After
1.2 1.3 1.2 1.3 1.3 1.3 1.3 1.4 1.3 1.6 l . 5 1.6
30% LECKANOL
14-DAY TANNAGE 124-HOUR T A N N A G E 114-DAY T A N N A G E
TANSAGE
1
... i:i ... ... 1.2 ... ...
1.3
...
. . , 1.6
Before
Grams 032f 0.13f 0.30~ 0.31f 0.33f 0.53f 0.26f O67f 0.70f 0.22f 1.19g 1.12f
Before
IGrams
...
...
... ... ... ... ... ... 1.5 1,s ...
... ...
::: ...
... " '
...
0.4jf 1.3if
... ... ... ...
I... 1
i
...
Grams
... ... ... ... ... ...
:. :. :.
... ...
1.4
0 17f l.?ig
1.4
...
...
fixed
1
::: ...
I
.,,
j
... . I .
...
Grams
... ...
::: , . .
...
, . .
... j
.: :. :.
...
...
+
(1) Syntan, (2) H2S04,(3) HzSOi NazSOA (equivalent to xatSO4 present in Leukanol, calculated from ash content). Refers to character of tanned specimens (g = good, f = fair, p = poor). c All Leukanol concentrations by volume. d Total quebracho solids not including Leukanol solids. a b
T a b l e 111-Effect
of C o n c e n t r a t i o n Using Q u e b r a c h o - S y n t a n Liauors
CONCN.OF TOTAL SOLIDS IN ORIGINALSOLN. Quebracho
Leuk- Added anol SarSO4
G./L G./L 0.075 ,. 0 225 .. 0.375 .. 0.750 .. 1.13 .. 1.88 .. 8.75 2.63 .. 12.50 3.75 .. 18.75 5.63 .. 25.00 7.50 .. 37.50 1 1 . 2 5 50.00 15.00 .. 5.01 10.03 15.04 25.07 37.6 . . . . . . 50.1 . . . . . . 6.25 ...... G./1. 0.25 0.75 1.25 2.50 3.75 6.25
. . . .
18.75 25.00 6.25 18.75 25.00
. . . .
.. .... .... .... ....
...... ...... . . . . 1.16 . . . . 3.47 . . . . 4.62
PH
GELA-
Before After
TEST
T I ~ -
SALT
TANNIN CHARACTER OF FIXED TAXNAGE
Grams 3.9 3.5 3.5 3.0 2.8 2.7 2.6 2.5 2.4 2 3 2.2 2.1
5.7 5 6 5.6 5 2 4.9 4.3 3.9 3.6 3 2 2.9 2.6 2.4
h-a t ural PH, about 4.6 2.7
2.8
2.4
2.8
2.3
2.6
2 . 7 3.6 2.4 3.0 2 . 3 2.9
Slightly
+
+ + +
Undertanned 0:02 Undertanned 0.10 Poor 0 . 2 1 Poor 0 . 3 7 Poor 0 . 7 6 Good 0.70 Good 0.79 Good 0.81 0.94 0.58 0.35 0.20 0.40 0.55 0.48 0.32 0.26 0 . 6 3 Fair (harsh 1black) 0.88 Fair (harsh f black) 0 . 5 3 Fair (harsh black) ' 0 . 5 7 Good 0.68 Good 0 . 5 4 Good
+
A loss of 0.05 gram was found here, evidence of lack of tannin and severe hydrolytic action of syntan. a
portions used for tannage of 2.000-gram samples of hide powder, according to the technic previously described. The results are summarized in Tables I11 and IV and Figures 4 and 5 and include not only data obtained by tanning with the above mixture, but also, for comparison, concentration data, previously reported, in which the vegetable extract alone had been used in tanning a t its natural pH. Further, a study was made of fixation of each extract, both with and without added sodium sulfate (in amount present in corresponding Leukanol mixture) and from solutions which had been titrated to p H values obtained for the corresponding Leukanol mixtures. These results are included in the tables and curves. Discussion of Results
The results show that small amounts of the syntan effect a greater amount of tannin fixed in a given time than that fixed from a pure quebracho solution a t the same pH value as that of the quebracho-syntan liquor. When the amount of the syntan is increased, however, the amount of tannin fixed in a given time is less than that from pure quebracho or from
quebracho plus sodium sulfate, all a t practically the same pH value. I n the case of viattle, it is seen in Figure 5 that the amount of tannin fixed is in general less from wattle-syntan liquors than from pure wattle solutions a t the same pH value, although greater than from wattle-sodium sulfate liquors. T a b l e IV-Concentration
F a c t o r , Using W a t t l e - S y n t a n L i q u o r s
COXCN. OF TOTAL SOLIDS IN ORIGINAL SOLS. Wattle
G./I. 10.0 25.0 50 0 75.0 100.0 150.0 10.0 25 0 50.0 750 100.0 150.0 10.0 25.0 50.0 75.0 100,o 150.0 5.1 12.8 25.6 51.2 89.6 128.0 192.0 a
&;:&:
Leukanol G./1. 3.0
7.5 15.0
22.5 30.0 45.0
..
..
.. .. .. ..
..
..
.. ..
.. .. .. .. ..
After
2.8 2.9 2.9 3.3 3.3 3.3 2.8 2.9 2.9 3.3 3.3 3.3 2.8 2.9 2.9 3.3 3.3 3.3
3.4 3.2 3.1 3.2 3.6 3.8 3.6 3.5 3.7 3.5 3.4 3.8 3.9 3.8 4.0 3.9 3.8
G./l.
.. .. .. .. ..
.. .. .. .. .. .. ..
1.8
....
Before
4.6
9.2 13.8 18.4 27.6
..
.. .. ..
..
.. ..
...
Satural p H about 4.2
TANNIN FIXED=
CHARACTER OF
Grams 0.73+ 0.65+ 0.43+ 0.18+ 0.21+ 0.20+ 0.65+ 0.70+ 0.6010.34+ 0.34+ 0.42+ O.56+ 0.41+ 0.41+ 0.32f 0.25+ 0.20+ 0.200.38-
Good, red-brown Good, red-brown Good, brownish Fair, brownish Fair, light tan Fair, light tan Good, dark brown Good, dark brown Good, dark brown Good, dark brown Good, dark brown Good, dark brown Good, dark brown Good, dark brown Good, dark brown Good, dark brown Good, dark brown Good, dark brown
TANKAGE
0.50+
0.29+ 0.12+ 0.09+ 0.08+
Signs refer to positive and negative gelatin-salt tests on filtrate.
One of the prime reasons for the advantages found for the presence of syntan is that it lowers the pH value of vegetable tannin liquors, thus increasing rate of fixation. It is to be noted, however, that the increase in fixation is greater than that obtained in pure vegetable liquors adjusted to the same pH but also containing sodium sulfate to the same extent as the vegetable-syntan mixtures. Consequently, the addition of syntan to a vegetable liquor confers qualities in addition to mere acidity. This was noted also in the character of the tanned hide powder specimens. Those tanned in vegetable-syntan liquors were softer and more "leathery" than those tanned in vegetable-sodium sulfate liquors, and the latter better than those tanned in pure vegetable liquors, p H being constant throughout. The first-mentioned tanned hide powders were also lighter in color. I n tanning practice it has been found that syntans may inhibit "dead tanning" or casehardening-i. e., excessive surface tannage of the
July, 1929
IXDCSTRIAL ALVDENGINEERING CHEMISTRY
hide. These facts would indicate that the organic matter in the syntan solution acts in a manner similar to certain organic non-taris. I n a previous publication from this laboratory - (3) . _it was shown that pyrogallol in low concentrations increases rate of tanning by tannic acid solutions a t pH = 2, while it inhibits the tanning a t high concentrations. This is similar to the action of the syntan reported in this paper. Within the limited scope of the experiments reported a t this time, it may be stated that a syntan increases rate of tanning of a vegetable extract due to its acid reaction, but with the advantage over the mere effect of lowered p H residing in some as yet-unexplainable qualities of the organic
701
matter present, the latter inhibiting "dead tanning" and producing a lighter colored tanned hide powder. Acknowledgment
The authon are pleased to express their appreciation for aid in this investigation received from A, F, Gallun of Milwaukee. Literature Cited (l) Bambergerp C h e m . - Z t g . , '1 318 (1919). (2) Kohn, Breeds, and Crede, J. Am. Leather Chew. Assocn., 11, I73 (1922). (3) Thomas and Kelly, IXD. END. CHEM..11, 41 (1925).
Effect of Pretreatment upon Hydrolysis of Hide Powder b y Saturated Calcium Hydroxide Solutions'" Arthur W. Thomas and Margaret W. Kelly DEPARTMENT OF
CHEhfISl'RY.
COLWlrBI.4 UNIVERSITY.
BSERVATIOSS in this laboratory on the behavior of gelatin have shown that when small blocks of gelatin jelly are thoroughly dried they will subsequently swell when placed in acid or alkaline solutions, provided the blocks have not been stored in the dried state for too long a time. Blocks a year old, or older, disintegrate when placed in acid or alkaline solutions. The strong forces of compression resulting from the attractive forces of the gelatin molecules in the dried bulk seem, therefore, to result in disruptive strains in the course of time. Since hides as received by the tanner may he fresh, wet ("green"), salted, or thoroughly dried, and in view of the gelatin phenomenon mentioned, i t was considered of value to find out whether desiccation or humidification of hide powder has any influence upon the loss of hide substance during subsequent soaking in limewater. Incidentally, since hide powder is preserved better in sodium sulfate than in sodium chloride solutions (@,* hide powder that had been soaked in saturated solutions of these salts was included in this study.
0
Pretreatment
Specimens of hide powder were subjected to the action of atmospheres of varying degrees of humidity until the protein had reached equilibrium with the moisture content of the atmosphere. Fifteen-gram portions of American standard hide powder were placed in dishes in the upper compartments of desiccators. The desired humidity was obtained by means of sulfuric acid solutions in the bottom of each desiccator. A small portion of hide powder in an open weighing bottle was also placed alongside of the 15-gram portion in order t o determine attainment of equilibrium as revealed by constancy of weight of the small sample. The pretreatments were carried out a t 0 and 50 per cent humidity I Presented before the Division of Leather and Gelatin Chemistry a t the 74th Meeting of the American Chemical Society, Detroit, Mich., September 5 to 10, 1927. Received March 6, 1929. 2 Contribution from the Chemical Laboratories, Columbia University.
KO.600.
* Italic numbers in parenthesis refrr t o literature cited a t end of article.
NEW
YORK,
N. Y
a t 37.5" C., and a t 0, 50, and 100 per cent humidity at room temperature and a t approximately 4' C. The hide powder exposed to an atmosphere saturated with water vapor a t room temperature underwent slight bacterid decomposition in 20 weeks, as evidenced by an unpleasant odor. A small amount of mold also appeared. At 37.5" C. and 100 per cent humidity the same sort of decomposition took place so rapidly and to such an extent that the sample was discarded a t the end of 8 weeks. I n each case, together with the foul odor, the weights of the small "pilot" samples showed a sudden decrease, thus further indicating decomposition into volatile products. At 4" C. slight evidence of this sort appeared a t 190 days. For the attainment of moisture equilibrium a t 50 per cent humidity the following time intervals were required-at 37.5" C. 50 days, a t room temperature 60 days, and a t 4" C. 190 days. At 0 per cent humidity the equilibrium times were a t 60 days 37.5" C., 90 days a t room temperature, and 150 days a t 4" C. All were kept under the conditions described, however, for 190 days. In the case of pretreatment with saturated salt solutions, samples of hide powder after 84 weeks' contact a t room temperature with the solutions were filtered off, washed thoroughly t o remove salt and soluble nitrogenous products, squeezed as dry as possible, and analyzed for water and ash content. Treatment with Limewater
After the specified pretreatment the samples of hide powder were transferred to stoppered bottles containing 300 cc. of saturated limewater. I n all cases this volume (300 cc.) was corrected for gain or loss in water content of the original 15-gram sample of hide powder. The limewater digestions were done a t room temperature. At the intervals noted in Table I portions of the liquids were pipetted out, filtered through a dry filter paper, and samples of the clear filtrates analyzed for nitrogen content by the Kjeldahl method. From the nitrogen content of the filtrate and the nitrogen content (2.346 grams) of the original 15-gram sample of hide powder, the per cent of hydrolysis
