RECENT WORK IN AGRICUTURAL SCIENCE. 



AGRICULTURAL CHEMISTRY— AGROTECHNY. 



Annual reports on the progress of chemistry for 1916, edited by J. C Cain, 

 A. J. Greenaway, and C. Smith {Ann. Rpts. Prog. Ghem. iLondon'\, IS {1916), 

 pp. YIII-\-28Jt). — This report corresponds to those of previous years (E. S. R., 

 35, p. 201). 



Pervaporation, perstillation, and percrystallization, P. A. Kober {Jour. 

 Amer. Chem. ,So(:, SiJ {1911), No. 5, pp. 9.'f4-9JfS, figs. 5). — Experiments are de- 

 scribed in which collodion bags or containers are used for the procedures of 

 evaporation, distillation, and crystallization. "Collodion and parchment mem- 

 brane containers permit water to evaporate through the walls as though no 

 membrane were present. This phenomenon is called pervaporation. Distilla- 

 tion by means of pervaporation is called perstillation, and can be conducted 

 at ordinary atmospheric pressure with low temperatures as well as with 

 vacuum. When a dialyzable constituent of a liquid within these containers 

 reaches saturation, crystallization usually takes place on the outside. This 

 phenomenon is called percrystallization." 



The theory of the phenomena is briefly discussed. 



On the quinone-phenolate theory of indicators: The electrical conductivity 

 of solutions of phenolsulphonphthalein and of its bronio and nitro deriva- 

 tives, E. C. White and S. F. Agree {Jour. Amer. Chem. Sac, 39 {1917), No. 4. 

 pp. 648-652). 



Eeducing matter extractable from filter paper, R. S. McBride and J. A. 

 ScHEBRER {Jour. Amer. Chem. Soc., S9 {1911), No. 5, pp. 928-933). — In the study 

 reported the authors conclude that some substance is extracted from the 

 filter papers ordinarily used which reduces permanganate. It is indicated as 

 being furfural or a closely related substance produced by oxidation and hydrol- 

 ysis of the cellulose. Washing the filter paper previous to use is indicated as 

 a great aid in avoiding excessive consumption of permanganate. Titration, 

 however, even in the presence of the paper is not considered objectionable. 



The preparation of hydrochloroplatinic acid by means of hydrogen peroxid, 

 P. RuDNicK and R. D. Cooke {Jour. Amer. Chem. Soc., 39 {1911), No. 4, pp. 

 633-635). — The following procedure is described: 



Ten gm. of dried (but not ignited) platinum black is covered with 50 cc. 

 of concentrated hydrochloric acid warmed to about 50 or 60° C. and 3 per cent 

 hydrogen peroxid slowly added. Just enough hydrogen peroxid is kept present 

 to maintain a moderate evolution of chlorin, which originates entirely on 

 the platinum. When the platinum has been entirely dissolved the solution is 

 evaporated to a volume of 100 cc. and is then ready for use. The use of 

 dilute peroxid may cause the volume to become too great, in which case it is 

 necessary to evaporate to a smaller bulk before all the platinum has been 

 dissolvefl. Hydrogen peroxid of from 20 to 30 per cent strength has been 

 found satisfactory In keeping down the volume of the solution. 



Earlier refere»ces to the use of hydrogen peroxid as an oxidiJier and the 

 mode of the reaction are noted and briefly discussed. 



409 



