474 



SORGHUM. 



action ; experience has shown, in the course of this work, that the point where 

 the color of the permanganate barely appears in the rapidly agitated liquid, is 

 nearly identical with the true end reaction. Some operators carry the titra- 

 tion a little further, until a faint rose tint is permanent for about two seconds. 

 Each man who has done this work, has carefully determined his titration error, 

 and all figures submitted have been corrected therefor. The iron solution works 

 best if very strongly acidulated with sulphuric acid. The most convenient 

 strength for the permanganate solution, is 4.892 grams to the liter, equal to .005 

 grams glucose for each cubic centimeter. 



In order to determine what errors there may have been in estimat- 

 ing glucose and sucrose by this method, the following experiments 

 were carried out. Every portion ofFehliug solution used, was heated 

 by itself in the steam bath for an hour, to determine if it remained 

 unreduced in absence of sugar. In all cases it was quite unchanged. 

 Several solutions of dry granulated sugar, containing about .10 percent 

 of impurities, were made of stich a strength that every S*^""'- contained 

 .5000 grams of pure sucrose, or, on inversion, .5263 of inverted sugar. 



Of solution No. 1, four portions were measured out of S'^"^* each, and 

 submitted to the usual course of analyses, with the following result : 



The specific gravity was found by the piknometer to be 1.034. The 

 solution contained, therefore, 9.67 per cent of sugar. By titration we 

 find 9.57 per cent of sugar, and polarization of the solution gave 9.63 

 per cent of sucrose. 



Of the solution No. 2, nine portions were taken of 5'^°'''" each, to six 

 of which (Nos. 1-6) S'^"^' of the usual dilute acid were added, and to 

 the remaining three, lO'^"''*; otherwise the usual course of analysis was 

 pursued. The entire lot was carried through simultaneously on the 

 same steam bath. The results were as follows : 



