RECENT WORK IN AGRICULTURAL SCIENCE. 



AGRICULTURAL CHEMISTRY— A6R0TECHNY. 



Studies in the physical chemistry of essential oils (Proc. Roy. Soc. Vic- 

 toria, n. ser., 27 (1915), No. 2, pp. 149-163, figs. 2). — Two papers are presented. 



I. The physical properties of mixtures of two terpene substances in relation 

 to those of the constituents, R. B. Drew and E. I. Rosenblum (pp. 149-155). — 

 The results of the study show that simple mixtures of two terpene compounds 

 follow the " mixture law " quite closely. Any divergencies are eliminated by 

 the use of certain formulas. For such mixtures the proportions of the con- 

 stituents can be calculated from the properties of the mixture, provided none 

 of the constituents are unstable. In such cases the deductions are unreliable. 



II. The physical constants of some terpenes and oxygenated derivatives 

 thereof, and their variation with temperature, E. I. Rosenblum (pp. 155-163). — 

 The influence of temperature change on the density, refractive index, and rota- 

 tion of a number of terpenes and allied substances has been investigated, and the 

 results are submitted in tabular and graphical form. 



Some numerical relations among the rotatory powers of the compound 

 sugars, C. S. Hudson {Jour. Amcr. Chcm. Soc, 38 (1916), No. 8, pp. 1566-1515). 



The isomeric alpha and beta hexacetates of a-glucoheptose, C. S. Hudson 

 and E. Yanovsky {Jovr. Amcr. Chcm. Soc, 38 (1916), No. 8, pp. 1575-1577). 



a-Crotonic acid, a soil constituent, E. H. Walters and L. E. Wise (U. S. Dept. 

 Agr., Jour. Agr. Research, 6 (1916), No. 25, pp. 1043-10Jt6, pi. i).— The authors 

 have isolated a-crotonic acid from a Susquehanna fine .sandy loam found in a 

 field near Marshall, Tex. The soil was of such a nature as to present op- 

 timum conditions for the formation and accumulation of organic acids. 



The acid was isolated from an alkaline extract obtained by treating the soil 

 with an aqueous 2 per cent sodium hydroxid solution for 24 hours at room tem- 

 perature. The extract thus obtained was slightly acidified with sulphuric acid 

 and filtered. The acid filtrate was extracted with ether, the ether extract 

 evaporated to about 2(X) cc, and aldehydes and similar substances removed by 

 treatment with sodium bisulphite. The bisulphite solution was extracted sev- 

 eral times with fresh ether, the ether extracts combined, and slowly evaporated 

 to a brown sirup in a small crystallizing dish. The dish was then covered with 

 a watch glass containing ether and maintained at a low temperature on a steam 

 bath. A white crystalline solid gradually sublimed on the watch glass. The 

 sublimed substance was dried between filter paper, recrystallized from pe- 

 troleum ether, further purified by subliming several times at a low tempera- 

 ture, and finally dried over anhydrous calcium chlorid. Physical and chemical 

 tests identified the material as a-crotonic acid. 



It is suggested that the acid is possibly formed in soils " during the destruc- 

 tion of cellulose, from /3-hydroxy acids of the aliphatic series, or by the hy- 

 drolysis of allyl cyanid, which is found in the essential oils from certain plants." 



Biochemical changes in cotton seed in storage, J. B. Rather (Jour. Indus, 

 and Engin. Chem., 8 (1916), No. 7, pp. 60^-607, figs. 2).— This material has been 

 essentially noted from another source (E. S. R., 35, p. 412). 

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