RECENT WORK IN AGRICULTURAL SCIENCE. 



CHEMISTRY. 



Analytical investigations of the hydrolysis of starch by acids, 

 G. W. Uolfe and (x. Defren [Jour. Amer. Chem. Soc, 18 (1896), No. 10, 

 pp. 869-900, Jig. 1, dgms. 7). — The experiments of the authors were 

 designed to determine whether there is any definite relation between 

 the optical rotation and the reducing power of the products of the 

 hydrolysis of starch, and whether the three products, maltose, dextrose, 

 and dextrin, are influenced by definite laws. It was found that there is 

 a constant relation between the rotatory and reducing power of the total 

 product even when the starch is hydrolyzed under very variable con- 

 ditions. Up to arotation of about 90° this relation may be expressed by 

 a curve corresponding to the equation: ./-' + //- + 4fi8,r — 046;/+1580=0, 

 where the abscissae are the changing values of the rotatory power 

 from amylodextrin (195°) to dextrose {[a] 386 =53.5°), and the ordinates 

 are the reducing power (K 386 ) when dextrose=100. 



In connection with this the authors attempted to determine the con- 

 stituents of commercial starch sugar by means of the Vent/ke saccha- 

 rimeter, for the purpose of control in the factory, and give a table for 

 calculating the rotatory power of solutions of 7.5 to 10° Brix. 



The hydrolysis of starch differs from that of sugar and salient since 

 starch is insoluble in water at the ordinary temperature and the amylo- 

 dextrin formed by hot water is somewhat soluble in cold water and 

 becomes more so as the temperature rises. Two reactions have to be 

 considered, viz, the hydrolysis of dextrin to maltose and the hydroly- 

 sisof maltose to dextrose. If A is the dextrin content at the beginning 

 and A — x the amount remaining after the time t. and c the constant 

 depending on the conditions of the hydrolysis we obtain — 



;J';=<-<A„-.r) 



from which by integration — 



1<>£ V A ° -=<?., or ] log A " =c, 

 A — x t A,, — x 



thegeneral equation for the first phase of the reaction. The hydrolysis 

 of the maltose to dextrose is peculiar, as it takes place simultaneously 

 with the decomposition of the maltose. In the hydrolysis of the dex- 

 trin the maltose content rises rapidly to a maximum of 44.1 per cent 

 with a rotation of 129 and then falls, while the dextrose increases 

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