DETERMINATION OF SUGARS IN GRAIN AND CATTLE FOODS. 13 

 TERMS USED IN STATING RESULTS. 



As bearing on the general subject of sugar determinations, a word 

 should be said regarding the methods of stating sugar results on such 

 products as cattle feeds and grains. Some chemists calculate the 

 reducing sugars to dextrose and some to invert sugar, while others 

 state the reducing power in terms of metallic copper reduced by a 

 given wftight of the material under examination. The expression 

 of the results in terms of sugars is more definite than in terms of copper 

 reduction, which gives no clear idea of the amount present. Indeed, 

 it is doubtful whether the reducing action noted is due to one particu- 

 lar sugar; it may be due to a mixture of several sugars or to invert 

 sugar which is a mixture of equal parts of dextrose and levulose. In 

 only a very few cases have the sugars been separated and identified. 

 Therefore, for general work it seems that sugars before inversion should 

 be reported as " Reducing sugars calculated as dextrose" or "Reducing 

 sugars calculated as invert sugar," depending on which calculation 

 was made. And for sugars after inversion the same phraseology 

 should be used, namely, " Total sugars calculated as dextrose" or 

 "Total sugars calculated as invert sugar." The increase in reducing 

 sugars after inversion may not be caused entirely by the inversion 

 of sucrose, but may be due to other compounds or sugars being split 

 up into reducing sugars by the acid. It is well known that the ordi- 

 nary inversion methods will hydrolyze other sugars, for instance, 

 raffinose, and may hydrolyze such compounds as inulin or some of 

 the glucosids and pentosans, forming reducing sugars. Under such 

 circumstances it is certainly wrong to calculate the increase in reduc- 

 ing sugars as sucrose without a more definite knowledge of these 

 sugars, although a part of this increase may be due to sucrose. 



In order to eliminate a number of these compounds and restrict the 

 increase to one or two sugars, the invertase inversion method proposed 

 by Hudson * should be used conjointly with the acid inversion. 

 Under such circumstances, should the quantity of total sugars agree 

 by both methods, one may safely say, with our present knowledge, 

 that the increase in reducing sugars is due to sucrose, raffinose, or 

 both. As the latter sugar is present in notable quantities in cotton- 

 seed meal, and may be in other materials, it is not altogether safe to 

 calculate this increase as sucrose with the idea that only sucrose is 

 present. By the invertase method many other substances are 

 eliminated. It seems better, therefore, to use the expressions (1) 

 "Reducing sugars calculated as dextrose," or "Reducing sugars 

 calculated as invert sugar;" (2) "Total su'gars calculated as dextrose," 

 or "Total sugars calculated as invert sugar," and (3) "Increase in 

 reducing sugars by acid hydrolysis (or by invertase) calculated as 

 sucrose." 



1 U. S. Dept. Agr., Bureau of Chemistry Cir. 50; J. Ind. Eng. Chem., 1910, 2: 143-5. 



