1917J AGRICin-rUBAJL OHEMISTEY — AGEOTEOHNY. 613 



treated with heat, heated forage inoculated with bacteria, and cured or dried 

 forage. Normal check fermentations were provided by siloing untreated forage. 



The untreated and inoculated forage all showed a marked increase tn acid 

 production, while the chloroformed and heated samples exhibited no Increase. 

 " Good clean-flavored silage resulted in every instance from the fermentation of 

 the untreated, green, cxired, and inoculated .forage. The treated forage, that 

 saturated with chloroform and that heated, exhibited no characteristics of 

 silage." Heat production was observed only In the untreated and inoculated 

 forage, with no indication of heating in any of the treated samples. The heat 

 production of the different kinds of silage is represented in graphical charts. 



From the Investigation It is concluded that " heat production in forage fer- 

 mentation results fi-om microbial activity and not from intramolecular respira- 

 tion of the tissue cells." 



The citric acid fermentation of Aspergillus niger, J. N. Ctjkbib {Jour. Biol. 

 Chem., SI {1911), No. 1, pp. 15-37, pis. 2, figs. 2).— The author has studied the 

 inorganic salt requirements, the general equation of metabolism, and tiie reac- 

 tion of the medium of the citric acid fermentation of A. niger. Prom observa- 

 tions of a large number of cultures, Iron is not considered necessary for the 

 development of spores. It is suggested, however, that some definite chemical 

 reaction involved in the utilization of nitrates is accelerated in the presence 

 of iron. 



The fermentation of a sugar by A. niger is considered an oxidation proceeding 

 in three stages and producing citric acid, oxalic acid, and carbon dioxld. The 

 proportion in which the products of the metabolism appear can be varied at 

 \vill. Qnlte different results are given by cultures, even imder the same condi- 

 tions, whicli can not be distinguished moi*phoIogically. By proper selection of 

 cultures and conditions the yield of citric acid can be varied from none at all 

 to over 50 per cent of the sugar consumed. Low nitrogen supply, high con- 

 centration of sugar, and nitrogen supplied as ammonium salts rather than as 

 nitrates are conditions especially favorable to the fermentation. Where the 

 nitrogen was supplied as ammonium salts or as asparagin, iron was not found 

 to stimulate the metabolic processes in any way. In the case of nitrates the 

 stimulating effect of iron, however, was especially noticeable in the increased 

 production of carbon dioxid and weight of mycelium. 



From the general consideration of the data obtained the following medium is 

 considered the most suitable for conducting the citric acid fermentation with 

 A. niger: Per 1,000 cc. of solution, saccharose 125 to 150 gm., NBUNOa 2 to 2.5 

 gm., KHJ»04 0.75 to 1 gm., MgSOi.TH-O 0.2 to 0.25 gm., HQ to Pg 3.4-3.5 

 (5-4 cc. fifth-normal). 



Influence of certain electrolytes upon the course of the hydrolysis of starch 

 by malt amylase, H. O. Shehman and Jennie A. Walkee {Jour. Amer. Chem. 

 Sac, 39 {1911), No. 1, pp. W6~U93, figs. 7).— The rate of formation of reduc- 

 ing sugar by the action of purified malt amylase on soluble starch, both in 

 neutral solution and in solution with the addition of regulated amounts of 

 hydrochloric or phosphoric acids or primary potassium phosphate, was investi- 

 gated. 



" When the activating electrolyte was added in such amount as to give op- 

 timum or nearly optimum concentration of hydrogen ion, the action of the 

 euzym was increased not only in the earlier stages but throughout the entire 

 range investigated. The greater the concentration of enzym the less the effect 

 of the added electrolyte. . . . Throughout the first half of the hydrolysis, or up 

 to a yield of half the theoretical amount of maltose, the rate of maltose forma- 

 tion from soluble starch was found to be proportional to the concentration of 

 substrate, at least in solutions containing favorable amounts of acid or acid 



