RECENT WORK IN AGRICULTURAL SCIENCE. 



AGEICTJLTURAL CHEMISTRY— AGRQTECHNY. 



The physical properties of colloidal solutions, E. F. Bttrton {London and 

 New York: Longmans, Green <£■ Co., 1916, pp. VII+200, figs. 18). — This volume 

 discusses the physics of colloidal solutions under the following topics : Prepara- 

 tion and classification of colloidal solutions ; the ultramicroscope ; the Brownian 

 movement; the optical properties of colloidal solutions; measurement of the 

 sizes of ultramicroscopic particles ; motion of colloidal particles in an electric 

 field, cataphoresis ; the coagulation of colloids ; theory of the stability of col- 

 loids; and practical applications of the study of colloidal solutions. A bibliog- 

 raphy of the literature cited is appended to each chapter. 



The influence of ethyl alcohol and glycerol upon the rate of solution of 

 casein by sodium hydroxid, T. B. Robertson and K. Miyake (Jour. Biol. 

 Chcin., 26 (1016), No. 1, pp. 129-lJt2, figs. 4).— The work reported has shown 

 that both alcohol and glycerol retard the penetration of casein particles by 

 16/l,0()0-normal sodium hydroxid. The penetration formula (E. S. R., 35, p. 712) 

 expresses the relationship between the quantity of casein dissolved and the time 

 of stirring in all the glycei'ol-water mixtures studied, and in alcohol-water 

 mixtures containing less than 4.5 or more than 7 molecules of alcohol. 



Further considerations on the effect of the concentration of alcohol and 

 glycerol are also set forth. 



A comparative study of the behavior of purified proteins towards pro- 

 teolytic enzyms, E. M. Frankel {-Jour. Biol. Chem., 26 {1916), No. 1, pp. 31-59, 

 figs. 4). — The experiments reported demonstrate that in pepsin-hydrochloric- 

 acid digestion pepsin is the effective agent, since hydrochloric acid, in the con- 

 centrations ordinarily employed, has very little proteolytic effect. 



It is concluded that comparable results in proteolysis studies are to be 

 obtained only when the substrates are in solution ; otherwise deviations of from 

 10 to 15 per cent may be encountered in duplicate experiments. A parallelism 

 in the cleavage curves of 13 proteins examined was observed, the cleavage being 

 calculated as the ratio of amino nitrogen liberated at any one time to that ob- 

 tained on total hydrolysis of the protein with strong acid. Pepsin-hydrochloric 

 acid was found to liberate about 20 per cent of the total amino nitrogen of a 

 protein in less than 100 hours. Trypsin acting on such partially digested pro- 

 teins effects a cleavage of about 70 per cent, while its action on native proteins 

 causes a cleavage of only about 50 per cent of the peptid linkages. Erepsin fol- 

 lowing the action of pepsin, was found to be a very effective agent in causing 

 the disruption of the protein molecule, about 85 per cent of the protein being 

 cleaved in the experimente reported. By the successive action of pepsin, trypsin, 

 and erepsin from about 85 to 90 per cent of the total amino nitrogen was found 

 to be liberated in the protein studitnl. 



The origin of the humin formed by the acid hydrolysis of proteins. — II, 



Hydrolysis in the presence of carbohydrates and of aldehydes, R. A. Gort- 



NER {Jour. Biol. Chem., 26 {1916), No. 1, pp. 177-204). — Continuing the work 



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