EXPERIMENT STATION RECORD. 



Vol. 38. Abstract Number. No. 6. 



RECENT WORK IN AGRICUETURAL SCIENCE. 



AGRICULTURAL CHEMISTRY— AGROTECHNY. 



The chemistry of colloids {New York: John Wiley d Sons, Inc., 1917, pp. 

 VI I +288, figs. 39).— Part 1 of this volume, by R. Zsigmondy, consists of a trans- 

 lation, by E. B. Spear, of the German edition (E. S. R., 28, p. 407). In part 2, 

 by E. B. Spear, certain industrial applications of colloidal chemistry are dis- 

 cussed, including smoke, riibber, tanning, milk, colloidal graphite, and clays. 

 The book closes with a chapter on Colloids in Sanitation, by J. F. Norton, 

 in which purification of wastes and sewage and the mechanism of disinfection 

 are discussed. 



Outline of colloid chemistry, I— III, W. D. Bancroft (Jour. Franklin Inst., 

 185 (1918), Nos. 1, pp. 29-57; 2, pp. 199-230; 3, pp. 373-387 ) .—Part 1 of this 

 paper discusses adsorption of gases, liquids, and solids, including the following 

 topics : Catalytic action of solids on gases, adsorption of gases and vapors by 

 solids and by liquids, adsorption of liquids by solids and by liquids, and ad- 

 sorption of solids by solids and by liquids. Phenomena illustrating each 

 phase of adsorption are noted. 



Part 2 discusses adsorption from solution and coalescence under the fol- 

 lowing heads : Adsorption from solution by solid, the adsorption isotherm, 

 abnormal adsorption, negative adsorption, reversibility of equilibrium, speci- 

 ficity of adsorption, adsorption of several solutes, adsorption from solution by 

 liquid, adsorption and surface tension, Brownian movements, coalescence of 

 liquids, coalescence of solids, and plasticity. 



Part 3 discusses the preparation of colloidal solutions, including types of 

 precipitates, theory of peptization, condensation methods, and dispersion 

 methods. Under condensation methods there are two subdivisions, in which 

 the stability is due chiefly to the presence of strongly adsorbed substances or 

 chiefly to the low concentration of agglomerating agents. Under dispersion 

 methods the subdivisions are disintegration by removing an agglomerating 

 agent, by adding a peptizing agent, by mechanical methods, by electrical 

 methods, and by electrochemical methods. 



On the swelling of gelatin in polybasic acids and their salts, M. H. Fischer 

 and Marian O. Hooker (Jour. Amer. Ohem. Soc, 40 (1918), No. 1, pp. 272-292, 

 figs. llf). — Experiments are described showing the amount of water absorbed by 

 gelatin discs immersed in different concentrations of the primary, binary, or 

 tertiary salts of phosphoric, citric, and carbonic acids. The swelling varied 

 not only with the salt but with its concentration. 



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