AGRICULTURAL CHEMISTRY — AGROTECHNY. 611 



less breakable, easier to operate, and more adaptable to field work than either 

 the standard sand aeroscope or the aeroscope recommended by Rettger. The 

 latter can be made to yield excellent results, provided sufllcient care is exer- 

 cised in handling it. Its use, however, is attended with a number of ditliculties, 

 among which may be mentioned its tendency to leakage about the rubber 

 stoppers after being sterilized, the foaming of the liquid during operation, and 

 the tenacity with which the bacteria cling to the inner surface of the moist 

 inlet tube. 



" The method of determining bacterial precipitation from air by means of 

 exposed Petri plates has been found to be entirely unreliable, as it gives a 

 measure of the number of bacteria-laden dust particles and not a measure of 

 the number of bacteria present. The number of bacteria precipitating upon a 

 given area has been determined by analyzing measured quantities of sterile water 

 which had been exposed to the air for a given length of time in sterile pails. The 

 numbers obtained in this way were from 2 to 32 times higher than those 

 obtained with the plate-exposure method." 



A bibliography of cited literature is appended. 



The differentiation of various kinds of yeast with the aid of specific 

 agglutinins, Lichtenstein-Kosenblat (Wchnschr. Brau., 31 (1914), pp. 293- 

 295; abs. in Ztschr. Angew. Chem., 21 (1914), No. So, Referatenteil, p. 592). — 

 Rabbits receiving intravenous injections of pure cultures of yeast yielded blood 

 sera which could be used in the agglutination test for differentiating not only 

 the various Saccharomycetes (top and bottom fermentation yeasts) but also for 

 differentiating torulas from Saccharomycetes. 



Picric acid as a titrametric standard, O. Pfeiffeb {Ztschr. Angew. Chem., 

 21 (1914), No. 50, Aufsatzteil, p. 383). — Picric acid is advocated as a substance 

 for iodometry and acidimetry. For standardizing acid solutions, however, the 

 author prefers measuring the strength of the original solution with alkali and 

 dimethylamidazobenzol. 



The titrametric estimation of free sulphurous acid, E. Kedesdy {Chem. 

 Ztg., 38 {1914), No. 51, pp. 601, 602; ahs. in Ztschr. Angew. Chem., 21 {1914), 

 No. 91, Referatenteil, p. 625). — The method in which sulphuric acid is titrated 

 with methyl orange until the acid sulphite stage is reached and then with 

 plienolphthalein until the neutral salt is obtained is deemed inexact, since the 

 change in color with pheuolphthalein occurs before the formation of the neutral 

 salt is complete. The transition from one stage to the other may be made 

 sharper if one oxidizes the acid salt to the neutral salt with hydrogen peroxid. 



A new simple method for determining free sulphurous acid when thio- 

 sulphate or sulphuric acid is present, A. Sander {Ztschr. Angew. Chem., 21 

 {1914), No. 26, Aufsatzteil, pp. 194, 195).— In this method, which is a modifica- 

 tion of Fold's, standardized iodiu solution is run in excess into the mixture of 

 sulphurous acid and thiosulpliate, and the excess of iodin is determined with 

 standardized thiosulphate solution. The colorless solution is then treated with 

 an iodid-iodate mixture and the liberated iodin is titrated with thiosulphate as 

 before. The method can be used for estimating bisulphates, and also sulphuric 

 and sulphurous acid in admixture. 



The chief cause of the loss of sulphuric anhydrid and of chlorin by 

 incinerating substances containing these constituents, J. O'Sullivan {Analyst, 

 39 {1914), No. 463, pp. 425-428) .—The conclusions arrived at are as follows: 



Although chlorids are decomposed and chlorin is lost on incinerating organic 

 substances containing chlorids, the sulphates of calcium, potassium, and sodium 

 are not appreciably reduced. Magnesium sulphate undergoes decomposition on 

 ignition unless a carbonate is present. In the absence of a carbonate the ash 



