AGRICULTURAL CHEMISTRY AGROTECHNY. 713 



hygroscopic moisture present. " Tlie increased hygroscopic moisture present 

 was due ahuost entii'ely to an increase in organic material or humus. In tlie 

 case of a pure peat tlie difference is as much as 1..5 per cent, while in a sand 

 with no organic matter the results agree. It would appear from this that when 

 a soil contains much organic material the loss of weight on heating to 100° C. 

 represents more than the hygroscopic moisture present in the soil, part of the 

 loss being made up of other volatile constituents which are driven off on 

 heating." 



On the basis of these results the carbid method is considered to be a rapid 

 and reliable means for estimating the hygroscopicity of soils. 



A note on the Hopkins-Cole reaction for protein, H. G. D. Beeidahl 

 (Biochem. Join:, 9 {1915), No. 1, pp. 36, 37).— Of the materials tried in an effort 

 to feduce the amount of oxidizing agents in fresh sulphuric acid and conse- 

 quently to give the best color in the ring produced, granulated zinc was found 

 to be the most practical for large quantities of acid. 



Modified Wohlg'emuth. method for the determination of amylase activity in 

 the presence of alkaloids, J. Bodnae {Kis6rlct. KiJzlem., IS {1915), No. 2, pp. 

 367-^72).— The original procedure (E. S. R., 20, p. 208) has been modified in 

 that the alkaloids which had been found to interfere with the color changes 

 are removed by extraction, after the reaction is complete, with a suitable 

 organic solvent. The alkali is then neutralized with hydrochloric acid and the 

 determination completed in the usual manner. 



Bacteriolog'ical methods in food and drugs laboratories with an introduc- 

 tion to micro-analytical methods, A. Schneider {Philadelpliia: P. Blakistott's 

 Son d Co., 1915, pp. y III +288, pis. 6, figs. 87).— As stated in the preface, the 

 volume is primarily intended as a guide to students who are interested in the 

 bacteriological examination of foods and drugs. Practical laboratory methods 

 for food examination are outlined and discussed. 



Investigations in regai'd to the determination of the starch content of 

 potatoes, H. J. F. De Vkies {Verslag. LandbouivJc. Onderzoek. Rijksland- 

 honwproefstat. [Netherlandsl, No. 18 {1915), pp. 1-82, pis. 3). — As indicated by 

 experimental data the specific gravity is not a reliable index to the starch 

 content of potato flours, a chemical analysis being the only means of determining 

 the true starch content. In manufacturing establishments where no laboratory 

 is available and the specific gravity method must be resorted to, the author 

 recommends the use of new tables for the determination of the starch content 

 from the specific gravity, and he prefers the Reinmann or Parow balance to the 

 Stohman method. 



The most accurate value for the starch content of a potato flour is found by 

 an indirect analysis, as follows: 100— (moisture at 120° C.+ash+soil ma- 

 terial+ether extract+protein+pentosans). Lower values, however, for the 

 starch content are obtained on the average by the Baumert-Bode and Ewers 

 methods than by indirect analysis, as on dissolving the starch according to 

 Baumert and Bode and Ewers, products which reduce Fehling's solution are 

 formed. The method of Ewers is recommended. 



Chemical testing of milk and cream, R. H. Shaw {U. 8. Dept. Agr., Bur. 

 Anim. Indus. Doc. A-7 {1916), pp. 38, figs, ^i).— This bulletin contains detailed 

 descriptions of methods for the determination of fat, total solids, specific gravity, 

 acidity of milk and cream, calculation of total solids by formula, and the 

 detection of preservatives. A list of chemicals and apparatus used in the 

 chemical analysis of milk and cream is appended. The subject matter is 

 treated in such a manner that it may be followed by those who have had neither 

 chemical training nor a course in milk testing. 



