AGRICULTURAL CHEMISTRY AGEOTECHNY. 315 



water bath at 67° C. The height of the fat column is then read. The total 

 solids of the cheese may be estimated by drying the cheese in the flask previous 

 to adding the sulphuric acid. 



The methods of determining fat in dry milk, cream, and milk are also 

 described. 



Concerning the measurement of diastase activity in plant extracts, C. O. 

 Appleman (At>s. in Science, n. ser., 41 {1915), No. IO4S, pp. 175, 17G). — " Several 

 methods have been proposed for the measurement of the velocity of diastase 

 activity in plant extracts. The procedure adopted by several investigators is 

 based ui>on the determination of the amount of reducing sugar, usually calcu- 

 lated as maltose, produced by the action of a ^lefinite amount of extract upon 

 an excess of soluble starch for a definite length of time at constant tempera- 

 ture. The Kjeldahl 'law of proportionality' is sometimes observed and some- 

 times ignored." 



The general inapplicability of the method for plant extracts is very strik- 

 ingly shown in the following, which refers to the diastase activity in glycerin 

 extracts from cold-storage potatoes: The number of milligrams of sugar at 

 40° C. per hour per 100 gm. of potato pulp, calculated as maltose, was 17 mg. of 

 total reducing sugar on March 28, and the total sugar was 3.6. On December 

 20 the former was 24.6 and the latter 3.7. On January 13 the amounts were 81.9 

 and 3.7, respectively. 



" Calculated on the basis of increase in total reducing sugars or maltose in 

 the extract after incubation with soluble starch, the tubers would show a very 

 marked increase in diastase with storage, but when calculated on basis of in- 

 crease in total sugar, the diastase activity remains practically constant. The 

 amount of sucrose in the tubers" increases with cold storage. It is extracted 

 with the diastase and is inverted at the incubation temperature, according to 

 the law of the mass action. Since nonreducing, hydrolyzable sugars are present 

 in many plant tissues and are subject to wide variation in the same tissue, 

 the above-described method in unmodified form is not reliable." See also a 

 previous note (E. S. K., 32, p. 129). 



Estimates of cholesterol in serum by gravimetric and colorimetric meth- 

 ods, P. G. Weston {Jour. Med. Research, 29 {1914), No. 3, pp. 457-464) .—This 

 is a continuation of work previously published <* and consists of a comparative 

 study of the gravimetric digitonin method with the author's colorimetric 

 method. For the experiments pure cholesterol prepared from gall stones, 

 human brains, and blood serum was used. Determinations were made of (1) 

 pure cholesterol, (2) impure cholesterol extracted from serum, and (3) impure 

 cholesterol extracted from serum plus a known quantity of pure cholesterol. 



" Known quantities of pure cholesterol subjected to the same process as that 

 employed in the extraction of cholesterol from serum yielded 99.44 per cent 

 according to the colorimetric estimates and 108.56 per cent by weight. Serum 

 to which 1 mg. of pure cholesterol had been added to each cubic centimeter 

 yielded an excess of 1 mg. per cubic centimeter according to the colorimetric 

 method and an excess of 1.3835 mg. by weight. In the 17 experiments in which 

 a known quantity of cholesterol was estimated by both methods the results 

 obtained by colorimetric estimation were uniformly more accurate than the 

 results obtained by weight." 



The use of the interferometer in agricultural investigations, H. Kappejt 

 (LandiD. Vei's. Stat., 83 {1914), No. 5-6, pp. 385-396; abs. in Ztschr. Angew. 

 Chem., 27 {1914), No. 37, Referatenteil, p. 298).— This apparatus is employed 

 for determining the refraction of fluids. It is said to be a decided improve- 



"Jour. Med. Research, 26 (1912), No. 3, pp. 531-546. 



