188 



SCIENCE 



[Vol. LV, No. 141G 



new method of tannin analysis. The revised 

 procedure gives the same results as the original, 

 but saves a great deal of time and labor and 

 increases the accuracy for unskilled analysts. To 

 make a determination by the revised procedure, 

 it is necessary merely to shake a fixed amount of 

 hide powder with a solution containing a known 

 amount of the soluble matter of the tanning 

 material until all tannin is removed from solu- 

 tion, washing the tanned powder in a special 

 device which prevents the loss of anything but 

 matter in solution, drying the washed powder 

 and weighing it. The increase in weight of the 

 dry hide powder is a measure of the tannin eon- 

 tent. All criticism raised against the new method 

 thus far has been refuted. 



Wattle bark tannin: E. O. Phillips. 



Measurement of the iron contamination of 

 chestnut extract: T. G. Greaves. 



Anthrax prophylaxis in the leather industry: 

 Alfred Seymour-Jones. Anthrax is caused by 

 a micro-organism which exists in two forms. It is 

 imported by materials such as hair, bristles, wool 

 and dried hides and skins, mainly from far east- 

 ern countries. The organism in its active form is 

 easy to kill, but tlie spore is highly resistant. For 

 wool, hair and the like, the British government has 

 erected an experimental plant at Liverpool, using 

 heat and formalin, which promises good results. 

 Such treatment obviously cannot be applied to 

 hides. Experiment has shown that with hides the 

 only practicable method to deal with the spore is 

 by soaking in weak acid solution. _ Here common 

 disinfectants, such as formalin and the carbolic 

 series, cannot be used, owing to their tanning 

 action. Using mercuric chloride at 1/5000 in 

 one per cent, formic acid, followed by a brine 

 bath to pickle the hides, has proved very success- 

 ful, and the cost should not exceed six cents a 

 hide. Anthrax can be prevented from entering a 

 country, as New Zealand has shown. Since 1909 

 there has not been a single case in the country, 

 clearly demonstrating the efficacy of sterilizing 

 material at the exporting port. 



A trip through the tannery on the inside of a 

 calfsUn: John Arthur Wilson. This lecture is 

 illustrated by microscopic projections thrown on 

 the screen at 2,000 diameters. Cross sections of 

 calfskin at various stages of the tanning process 

 are shown. In fleshing, the adipose tissue is cut 

 away just under the flesh layer of elastin fibers. 

 During liming, the substance of the Malpighian 

 layer of the epidermis is slowly digested, thus 

 effectively separating the corneous layer of the 

 epidermis and the hairs from the dermis. In 



bating, the elastin fibers are digested by pan- 

 creatic enzymes. After bating only the grain 

 membrane, collagen fibers, erector pili muscles 

 and a few blood vessels are left. The tannin 

 combines chemically with the collagen fibers. 

 The fat liquoring process distributed oil uni- 

 formly over the surfaces of the fibers. Color- 

 ing and the application of finishing materials 

 complete the processes of addition. Chrome 

 tanning gives a very markedly different leather 

 from the vegetable process. 



0?i the hydrophobic colloid content of vegetable 

 tanning extracts with attempts to correlate 

 astringency with the potential difference of the 

 particles against the aqueous phase: Arthur W. 

 Thomas and Stuart B. Foster. The reasons for 

 the different degrees of astringency of various 

 vegetable tanning extracts have been long a 

 matter for speculation. The problem has been 

 attacked from a colloid chemical point of view 

 with the result that astringency has been indicated 

 to be a function of the electrical charge of the 

 tannin particles. The higher the charge the 

 greater is the astringency. The electrical charges 

 for several extracts are submitted and methods of 

 varj-ing these charges and incidentally the astrin- 

 gencies of extracts are suggested. As a result of 

 such discoveries blind use of certain vegetable 

 extracts is no longer necessary, since the prop- 

 erties peculiar to one kind can be obtained with 

 an entirely different extract by simple treatment 

 according to the principles of colloid chemistry. 



The time and concentration factors in the com- 

 bination of tannin with hide substance. I. Gam- 

 bier. II. Quebracho: Arthur W. Thomas and 

 Margaret W. Kellet. This paper is the first of 

 a series of studies of the action of vegetable tan- 

 ning extracts in the formation of leather. It 

 brings out clearly the difference in behavior of 

 an astringent tanning agent and of a mild one. 

 Gambler shows slow regular increase in the 

 amount of tans fixed by hide as the concentration 

 of the extract and the time of reaction is 

 increased. Contrasted to this behavior, que- 

 bracho shows a rapid and larger amount of tan 

 fixed than gambler does, accompanied with a 

 sharp maximum followed by an abrupt drop in 

 the fixation. The results of this investigation 

 combined with other researches from this labora- 

 tory are pointing to a scientific explanation of 

 the astringency of vegetable tanning materials 

 which will afford more intelligent control of them 

 in the tannery. 



Charles L. Parsons, 



Secretary. 



