410 EXPERIMENT STATION EECORD. [Vol.41 



ether after washing with alkali. The enzyms were allowed to act upon a 1 per 

 cent dispersion of the boiled starch for 30 minutes at 40° C, using such an 

 amount of the enzym solution as would result in the formation of about one- 

 third to one-half of the theoretically possible amount of maltose, and finally 

 determining the reducing sugar formed by titration against Fehling's solution. 

 The results, which are expressed in tabular form in percentage of starch di- 

 gested in 30 minutes, may be summarized as follows : 



AVhen similarly purified by washing with a very dilute alkali, wheat, maize, 

 and rice starches were all transformed into reducing sugar at essentially the 

 same rate whatever the digestive agent. When washed with water only, po- 

 tato starch was almost pure, but the cereal starches appeared to contain suffi- 

 cient amounts of fatty or waxy matter to interfere appreciably with the action 

 of the enzyms. This was true to a greater extent of the maize than of the 

 wheat starch, a result which emphasizes " the importance of such preparation 

 of maize products as shall insure their very thorough mastication and admix- 

 ture with saliva." The removal of the fatty matter by ether tended to increase 

 the rapidity of digestion of the cereal starches, but not always to the same ex- 

 tent as purification with dilute alkali. 



The rate of enzymic hydrolysis of potato starch was in general equal to or 

 slightly greater than that of the cereal starches. This is in agreement vplth 

 preliminary results obtained in the same laboratory by K. Hattori in a study 

 of the comparative rate of liydrolysis of rice and potato starches by means of 

 - saliva. A slightly higher yield of reducing sugar was obtained from the potato 

 than from the rice starch, the difference increasing gradually with the extent 

 of digestion. 



The growth of certain bacteria in media of different hydrogen-ion concen- 

 trations, B. Cohen and W. M. Clark {Jour. Bad., i {1919), No. 4, pp. 409-427, 

 figs. 4). — An investigation of the influence of pH upon rates of growth of bac- 

 teria during that period in the life history of a bacterial culture commonly 

 known as the period of logarithmic increase is reported from the Bureau of 

 Animal Industry, U. S. Department of Agriculture. The results obtained are 

 summarized as follows: 



" There is a broad zone of pH within which the rates of growth are quite 

 uniform for those short periods during which the increase of viable cells ap- 

 proaches the logarithmic rate. On the borders of these zones of pH slight 

 change in the pH produces a marked effect upon reproduction. The acid border 

 shifts with the nature of the acid. A distinct difference between the effect of 

 hydrochloric and that of acetic acid was noted. While no distinct optimum 

 reaction was found when only the logarithmic increase was considered, more 

 distinct optima appear when longer periods of growth are observed. The 

 period of ' lag ' is more pronounced in alkaline than in acid media. Evidence 

 is presented which suggests that the effect of pH upon specific fermentative 

 processes, upon reproduction in its several stages, and upon rates of death must 

 be kept distinct." 



The use of coal as a substitute for talcum to induce rapid boiling, E. C. 

 • Kendall {.Jour. Amer. Cheiii. Soc, 41 {1919), No. 8, pp. 1189, ii90).— Anthracite 

 coal has been found to be an ideal agent for bringing about the rapid boiling 

 of a solution and for preventing bumping in Kjeldahl flasks and in the distil- 

 lation of organic liquids. One or two pieces about 1 cc. in size are considered 

 better than many smaller pieces. The coal becomes less active after being kept 

 under water for some time, but can bo reactivated by heating in an oven. 



The use of turpentine resin in turpentine as a foam breaker, E. C. Kendall 

 {Jour. Biol. Chem., 38 {1919), No. 3, p. 529).— The author has found that from 

 1 to 2 cc. of a 20 per cent solution of resin in turpentine is very efficient as a 



