414 EXPERIMENT STATION RECORD. [Vol.43 



"The apparatus consists of a dark box 12.5 in. long. 4.5 in. wide, and 8 in. 

 high, having a darlv compartment at eacli end for the standard lights, next to 

 tliese the small dark compartments for the cell of unknown substances on the 

 one side and the standards on the other, a very small compartment in the 

 middle for the paper with its oil spot, and the narrow mirrors which rellcet the 

 images of the spot througli a small eyepiece directly in front." In using the 

 instrument the unknown solution is put into the cell to the left, the lights are 

 turned on, and wheels which control the standard ground glass discs are turned 

 until the intensities of illumination are balanced. By comparing the reading 

 thus obtained with a scale which has previously been worked out for the sub- 

 stance in question the turbidity can be calculated. 



Some observations on colorinietric estimations with solutions contain- 

 ing two colored substances, K. G. Falk and H. M. Koyes (Jour. Jiiol. Chon., 

 42 {1920), No. t, pp. 109-130).— The authors report a study of the conditions 

 involved in the colorinietric determination of reducing substances present In 

 ordinary urine by the method developed by Benedict and Ostei'berg. Follow- 

 ing a theoretical discussion of tlie significance of colorimetric determinations, 

 a series of experiments is reported involving matching in the Duboseq colorimeter 

 picrate against picrate, bichromate against bichromate, picramate against 

 picramate, picramate against bichromate, picramate plus picrate against picra- 

 mate plus picrate, and glucose-picrate product against picramate plus picrate. 



The variations in results with differing concentrations and alkalinities in- 

 dicate that the conditions under which accurate and comparative results may 

 be obtained are very limited, especially with regard to the concentration of 

 glucose which may be estimated accurately. " In order to be certain of quantita- 

 tive results, the standard and unknown solutions, containing two colored sub- 

 stances, should be very nearly alike in composition and concentration. The 

 errors introduced otherwise may be considerable." 



A rapid method for the determination of carbon in organic mixtures, 

 particularly urine, L. Lescoeur and O. Duteteux {Coiiipt. Rend. Soc. Biol. 

 [Paris}, 82 {1919), No. 34, pp. 1417, I4I8).— The method consists essentially 

 in fusing the material with sodium hydroxid and sodium nitrate- and deter- 

 mining the amount of sodium carbonate formed. The fusion is conducted in 

 a silver crucible provided with a cover and special outlet tube. 



Rapid determination of carbon, M. L. Lescoeur {Jour. Pharm. et Chim., 

 7 ser., 21 {1920), No. 7, pp. 257-263).— Essentially noted above. 



Fat determination in dehydrated potatoes, O. Matzdokff and W. KiJHNE 

 {Cliem. Ztcj., 44 {1920), No. 15, p. i03).— Determinations of the fat content of 

 various commercial products of dehydrated potatoes before and after hydrolysis 

 of the starch are reported. While the results in general were higher after 

 hydrolysis of the starch, one or two were lower. The authors conclude that 

 the fat content is so low in dried potato preparations that accui'ate results can 

 not be expected in this determination. 



Examination of frozen egg products and interpretation of results, H. W. 

 Redfield {U. S. Dept. Agr. Bui. 846 {1920), pp. 96, figs. 5).— This bulletin con- 

 sists of outlines of standard methods found suitable by the Bureau of Chemistry 

 for the chemical and bacteriological examination of frozen egg products to 

 determine the presence of decomposed material, and a demonstration that the 

 methods selected give concordant results in the hands of different analysts and 

 in the examination of matei'ial of given quality from diverse sources. The 

 determinations called for are total solids, ether extract, acidity of fat, ammonia 

 nitrogen, reducing sugar, indol and skatol, and the enumeration of viable 

 bacteria, total bacteria, and Bacillus coli. Parallel analyses by four or five 



