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Vol. 15, No. 4
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Direct Determination of the Plumping Power of Tan T
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Liquors’ By John Arthur Wilson and Albert F. Gallun, Jr. A. F. GALLUN& SONSCo., MILWAUKEE, WIS.
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H E DEGREE to which skin is plumped in tan liquors is a matter of great practical importance, and concerted efforts have been made to devise a means for measuring the degree of plumping under known conditions. Claflin2proposed a method in which a fixed quantity of hide powder was shaken with a known volume of the tan liquor, after which the mixture was filtered and the volume of filtrate taken as a measure of the plumping power of theliquor. Modifications of this procedure have been suggested from time to time, but all methods thus far proposed have been lacking in sensitivity and have failed to make a direct determination of plumping power, relying in each case upon the action of hide powder.a The term “plumping” is used by the tanner to indicate an increasing resistance of the skin to compression, whichis due to both the swelling of the protein matter of the skin and the changes in properties which this protein matter undergoes during its conversion into leather. In studying the effect of change of hydrogen-ion concentration upon calfskin, the writers4devised a Fro. I-EFVECT OF LACTIC ACID UPON method which apTHE PLUMPINQ POWEROB A TAN LIQUOR pears to he capable CONTAINING 25 G. OB OAK-BARK EXTRACT of measuring the PER LITER plumping power of tan liquors directly and with great accuracy. The resistance to compression of a piece of skin is first measured under standard conditions. The same piece is then put into the tan liquor whose plumping power is to be determined. The extent of plumping changes as the tan liquor diffuses into the skin, and may be measured for any given lapse of time by withdrawing the piece of skin and again measuring its resistance to compression. The degree of plumping is measured by the ratio of the resistance to compression of the skin after being taken from the tan liquor to its resistance to compression under standard conditions. The sensitivity of the method depends upon the sensitivity of the determination of resistance to compression, and there are thickness gages on the market capable of making this measurement with a sensitivity far greater than is necessary for work of this kind. The method is outlined in the following description of its use for measuring the effects of acid and salt upon the plumping power of an oak-bark liquor. A piece was selected from 1. Presented before the Division of Leather Chemistry at the 64th Meeting of the American Chemical Society, Pittsburgh, Pa., September 4 to 8, 1922. 2 J . A m . Leathev Chem. Assoc., 16 (1920). 234. a V. J. Mlejnek, et al., I b i d . , 17 (1922), 341. 4 THIS JOURNAL, 16 (1923), 71.
the butt of a calfskin, after liming, unhairing, and washing, of as nearly uniform thickness as possible and cut into squares having a side of about 2 cm. These squares were delimed by washing with several changes of 0.01 M HC1 containing 10 per cent of NaC1, then kept over night in a saturated solution of NaHCOa containing 10 per cent of NaCI, washed thoroughly, and finally bated for 5 hrs. a t 40’ C. in a solution of 1 g. per liter of pancreatin, having a pH value of 7.6. The pieces were then washed for 24 hrs. in running tap water, and were kept under distilled water in a refrigerator a t 7’ C. until used. It was found possible to prepare a month’s supply of these squares at one time, there being little or no sign of any decomposition taking place at this low temperature. The resistance to compression of any piece of skin was measured by means of a Randall and Stickney thickness gage with a flat, metal base, upon which the piece of skin was placed, and a plunger, having a circular base 1 sq. cm. in area, capable of pressing on the surface of the skin under constant pressure. The gage reading was taken, in every case, exactly 2 min. after dropping the plunger onto the skin. TABLEI-TAN LIQUORCONTAINING 25 G, OF OAK-BARK EXTRACT PEE LITER,AND LACTIC ACIDAND SODIUM CHLORIDE AS SHOWN IN TABLS MOLS FER LITER GAGEREADINGS MY. Final pH Lactic Sodium (AVERAGE OF TRIPLICATES) Value Acid Chloride Initial Final Ratio at 25O C. None None 1.346 2.150 1.60 4.63 0.0025 None 1.411 2.343 1.66 3.94 0.0050 None 1.383 2.699 1.95 3.74 0.010 None 3.842 1.433 2.68 3.47 0.025 None 1.470 4.564 3.10 3.05 0.050 None 1.360 4.497 3.31 2.51 0.100 None 1.434 5.100 3.56 2.52 0.100 0.100 0.100 0.100
0.05 0.10 0.25 0.50
1.456 1.458 1.461 1.420
4.522 3.918 3.483 2.152
3.11 2.69 2.35 1.54
2.49 2.47 2.43 2.37
Eleven tan liquors were prepared as indicated in Table I. The gage readings of pieces of the standard skin were taken and the pieces were then shaken with water to bring them back to their normal shape after being compressed in the gage. They were , then put into the tan $ 3 0 ‘ liquors and allowed p . to remain there for & : 24 hrs. a t 200 C. I n each case three pieces & . were put into 100 cc. of liquor. The final $,o. gage readings were : then taken. The re:: sults are shown in g j 01 0 2 0.3 04 0.5 Table I and in Figs. a“ Mols Sodium Ch/ur/de perL/fer 1 and 2. The plumpFIG. 2-REDUCTION BP SALT OF TXE ing action of acids PLUMPING POWEROF A TAN LIQUORCONand the repressing TAINING 25 G. OB OAK-BARKEXTRACT AND influence of salt are 0.10 MOLOF LACTICACIDPER LITER clearly shown. This method has the advantage of being able to duplicate exactly the conditions of the tan yard. As the standard, skin may be taken in the condition in which it normally
April, 1923
INDUSTRIAL A N D ENGINEERING CHEMISTRY
enters the tan vats. The chief precaution is that all pieces to be compared must be uniform at the time of taking the first gage readings. The pieces may then be put into actual yard liquors. A direct means is thus afforded of rating the plumping powers of tan liquors in actual use on a large scale. Using only ordinary care in the preparation of the test
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pieces of skin, we found a deviation of only 40.07in testing the solutions described in Table I with different pieces of skin; in half the total number of determinations the differences were 0.03 or less. The method obviously may be applied to the determination of plumping power of any kind of solution.
An Improved Method for the Determination of Alpha-, Beta-, and Gamma-Cellulose* By M. W. Bray and T. M. Andrews FOREST PRODUCTS LABORATORY, DEPARTMENT OF AGRICULTURE, MADISON,WIS.
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The following improved method for the determination of a-,p-, Wholly by difference- In HE determination of and y-cellulose, based upon the titrafion of organic material in order to Check the Percenta-,P-1 and Y-celluCross and Bevan cellulose, is more accurate and can be carried out ages of a-, P-, and T-cellulose is a measure of the resistance Of cellulose much more rapidly than the gravimetric method. It gives a direct lose in the gravimetric method, i t is necessary to to the action of 17-5 Per means for the estimation of cy-, p-. and y-cellulose. None of the cent sodium hydroxide.’ constants are obtained wholly by diflerence, as is fhe case in the repeat the Cross a d Bevan gravimetric method. Filtration and washing dificulties of the gravdetermination, which is The application of this dea long, ~ediousProcess. imefric method are practically overcome in the volumetric method. termination to Pulp cooked Check determinations can be made without repeating the Cross and The change in the graviby Various methods offers a means of evaluating these Bevan chlorination, as is necessary in the gravimetric method. metric method suggested pulps and possibly a way of by Opfermann,’o which showing the relation of one consists of washing the method of cooking to another and of establishing the charac- a-cellulose with dilute alkali instead of water in separating ter of the cellulose resulting from the cooking and bleach- i t from the nonresistant cellulose, gives more concordant ing processes.3 This determination affords valuable data also results, the separation appearing to be much more complete. in the study of decay of wood and wood pulp, showing the This improvement has beenused satisfactorily in connection change of resistant to nonresistant cellulose during decaya4 with the authors’ volumetric method. Practically the first work mentioned on the differentiation VOLUMETRIC METHOD of cellulose into a-, 6-, and y-cellulose is that of Cross and Bevan,6 who used this determination in the estimation Of Because of the difficulties in the gravimetric method and normal celullose. The method for the determination of to obviate the necessity of weighing, the oxidation method CY-, &, and y-cellulose cellulose obtained by the chlorina- proposed by Bronnert11 for “hemicelluloses” has been extion method, as worked out in the Cross and Bevana labora- tended and modified by the authors to provide a volumetric tory and described by Jentgen,’ with but slight modifica- method of analysis. tion, has been used in the Forest Products Laboratory for a Theoretically, cellulose is decomposed as follows upon oxidanumber of years, in connection with the chemical analysis of tion with potassium dichromate in sulfuric acid solution: American woods.8 It has also been used in the analysis of CsHloOs 602 = 6C02 5Hz0 cattle food consisting of hydrolyzed sawdustl9in the study of The calculations for the theoretical amount of potassium decay of wood and pulps,4 and in the study of the effect of dichromate necessary for the reaction, together with the bleaching of pulps,3 method of preparation of solutions, are given in Bronnert’s GRAVIMETRIC METHOD work. A number of difficulties and errors are encountered in the STANDARDIZATION OF POTASSIUM DICHROMATE SOLUTION gravimetric method of determining a-,@-,and y-cellulose. Since the potassium dichromate solution is to be used in This method necessitates careful washing of a- and @-cellulose to completely free them from impurities, and drying without oxidizing cellulose from pulps, it is standardized against decomposition is very difficult. Cumulative errors introduced cellulose obtained by the chlorination method12of Cross and in the determination of a- and @-cellulose are included in Bevan from sulfite pulp. The cellulose equivalent so obthe determination of y-cellulose, as this constant is estimated tained is used in preference to the theoretical value. Approximately 1 g. of cellulose (not corrected for ash), 1 Presented before the Division of Cellulose Chemistry at the 64th Meetdried at 105” C., is taken from a weighing bottle and placed ing of the American Chemical Society, Pittsburgh, Pa., September 4 t o 8, in a 250-cc. beaker. This is triturated with 30 cc. of 72 1922. * Jentgen, Z.Kunsfstoffe,1 (1911), 165; Piest, Z . angew. Chem., 26 (1913). per cent sulfuric acid and allowed to stand until solution is 24. complete. The sulfuric acid solution is transferred to a * Wells. TEISJOURNAL,13 (1921), 936.
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Bray and Staidl, Ibzd., 14 (19221, 35. “Researches on Cellulose,” 1900-1910, Vol. 111, p. 23. 6 “Paper Making,” 1916, p. 97. Lac. cit.; W a g . Jahr., 67 (1911), 426; 2.ongew. Chem., 24 (1911), 1341; Schwalbe, “Chemie der Cellulose,” 1911, p. 637. 8 Ritter and Fleck, THISJOURNAL, 14 (1922), 1050; Mahood and Cable, Ibid.. 14 (1922). 727. * Sherrard and Blanco, Ibid., 13 (19211, 61 4
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10 “Die Chemische Untersuchung pflanzlichen Rohstoffe und der daraus abschiedenen Zellstoffe,” translated by C. J. West, Paper, 8 (1921).
19. 11 “Die Chemische Untersuchung pflanzlichen Rohstoffe und der daraus abschiedenen Zellstoffe,” translated by C. J. West, Paper. 18 (1921), 21; Schwalbe and Sieber, “Die Chemische Betriebskontrolle in der Zellstoff und Papier Industrie,” p. 151;Schwalbe, “Chemie der Cellulose,’’ 1911, p. 637. 1* Schorger, TEIS JOURNAL, 9 (1917), 556.
