548 



SCIENCE 



[Vol. LVI, No. 1454; 



thus prevents it from attacking t)ie soft Mal- 

 pighian layer below. When a skin lias previousty 

 been swollen by acid or alkali, and the corneous 

 layer rendered softer and more permeable, a solu- 

 tion of pancreatin at 40°, even under toluene, 

 will not only destroy the Malpighian layer of the 

 epidermis and loosen the hair, but it will also dis- 

 solve the elastin fibers of the skin, thus effecting 

 both unhairing and bating in a single bath. 



A study of the strength of proteolytic enzymes 

 ill the process of hating: Charles S. Hollander. 

 During comparative tests of bating with dung 

 bates and with pure eiizymes, tests were made at 

 intervals of the strength of enzyme in the liquors, 

 by the casein method. The concentration varied 

 considerably with time in the case of the dung 

 but remained practically constant when pure 

 enzpne preparations were used. 



The hydrolysis of collagen hy trypsin: Arthur 

 "W. Thomas and Frank L. Setiiour-Jones. It 

 is shown that collagen is readily digested by 

 trj-psin under proper conditions, and that it is 

 umiecessarj' to subject collagen to chemical or 

 pepsin pretreatment in order to render it vul- 

 nerable to trj-ptic action. This refutes the gen- 

 erally accepted belief based on the statement of 

 Kuehne (1887) that trypsin can not hydrolyze 

 collagen. 



The points of 'minimum plumping of calf skin: 

 JoHjT Arthur Wilson" and Albert F. Gallun, 

 Jr. a study was made of the change in degree 

 of plumping of calf skin at different acidities 

 and alkalinities. There are two points of mini- 

 mum plumping, one occurring at a value of 5.1 

 and the other at 7.G on the jjj^ scale. Available 

 data seem to indicate that these two points of 

 minimum represent two different forms of skin 

 protein, one stable only in acid solution and the 

 other in alkaline solution. 



Direct determination of plumping power of tan 

 liquors: John Arthur Wilson and Albert F. 

 Gallun, Jr. The degree of plumping of skin in 

 a given tan licjuor is measured \)j the ratio of its 

 resistance to compression when taken from the 

 tan liquor to its resistance to compression under 

 standai-d conditions. The method can be con- 

 ducted with extreme sensitivity and is capable of 

 making the measurement in actual tannery prac- 

 tice. 



Effect of hydrogen-ion concentration upon the 

 analysis of vegetable tanning materials: John 

 Arthur Wilson and Er"\vin J. Kern. The per 

 cent, of tannin found bj- the A. L. C. A. official 

 method increases with ji value to a maximum at 

 8 and then decreases rapidly towards zero. On 



the other hand, Pj^ value appears to have no. 

 effect upon the determination by the Wilson-Kera 

 method over the range 3.6 to 7.3, but the rate of' 

 tanning of hide powder decreases rapidly witk 

 increasing p^ value a.bove 7. The rate of filtra- 

 tion of tan liquors is markedly affected by change- 

 of Pjj value, which may be attributed to changing- 

 degrees of dispersion of some of the solid matter. 

 The addition of lime to tan liquors causes a pre-' 

 cipitation of tannin, but only at p„ values, 

 above 7.2. 



Stahility of the hide-tannin compound at dif- 

 ferent Pjj values: John Arthur Wilson antJ 

 Erwin J. Kern. Leather is resistant to washing 

 in neutral or acid solutions, but is broken up into, 

 protein and tannin by alkaline solutions. The- 

 decomposition begins at Pj^ = 7.7 and proceeds, 

 at an increasing rate as the Pj^ value is raised' 

 above this value. 



The concentration factor in the fixation of tan- 

 nins hy hide suhstance: Margaret W. Kelly. 

 The relationship between degree of fixation of' 

 tannin hy hide substance and the concentration, 

 of the vegetable tanning liquors has been worked 

 out for a number of important extracts. All 

 show a steadj' increase in tannin fixed, as con-, 

 centration increases, up to a maximum tannage- 

 followed by a sharp drop in more concentrated^ 

 liquors. 



The hydrogen-ion and time factors in the fixa- 

 tion of tannins hy hide suhstance: Margaret W. 

 Kelly. The combination of vegetable tannins, 

 with hide substance is shown to depend upon the- 

 hydrogen-ion concentration of the liquor to a 

 most pronounced degree. Over a broad range of" 

 hydrogen-ion concentration, an M-shaped tannage- 

 curve is obtained. In acid solutions the greatest 

 fixation is oMained at Pjj-j- = 2 to 3, falling off 

 at greater acidities. On the less acid side of 

 p J- ^ 2 to 3, the fixation decreases to a mini- 

 mum at Pjj-|- = 5, the isoelectric point of col- 

 lagen, then increases to a second maximum at 

 Pjj-j- ^ S, and at greater alkalinities falls off" 

 approaching zero. The second maximum at- 

 p -|- = 8 is much lower than the principal maxi- 

 mum fixation at Pj.j-r = 2 to 3. Explanation for- 

 tius behavior is submitted in the original paper. 

 The influence of neutral salts upon the fixation 

 of tannins hy hide suhstance: Arthur W. 

 Thoiias and Margaret W. Kelly. Both sodium, 

 cliloride and sodium sulfate decrease the fixation 

 of vegetable tannins by hide substance at 

 p -j_ = 3; sodium sulfate to a, greater extent than, 

 sodium chloride. At Pij+ = 5, sodium ehloride- 

 iu low concentrations promotes the fixation; at 



