GLUCOSE AND GRAPE-SUGAR. 253 



trade have optical and chemical properties quite different from many 

 other substances bearing the same name. 1 shall use the words in the 

 signification explained above. 



Properties of Glucose. Glucose is a thick, tenacious sirup, 

 almost colorless, or of a yellowish tint. It has an average specific 

 gravity, at 20 C, of 1-412. That which is made for summer con- 

 sumption is a little denser than that manufactured for winter use. 

 This sirup is so thick that, in the winter, it is quite difficult to pour it 

 from one vessel to another. 



The sweetness of glucose i. e., the intensity of the impression it 

 makes on the nerves of taste varies greatly with different specimens. 

 Some kinds approach in intensity the sweetness of cane-sugar, while 

 others seem to act slowly and feebly. It has been shown that the 

 degree of sweetness depends on the extent of the chemical changes 

 which go on in the conversion of starch into sugar. When the process 

 of conversion is stopped as soon as the starch has disappeared, the 

 resulting glucose has a maximum sweetness.* The color of glucose 

 depends on the thorough washing of the substance, during the process 

 of manufacture, through animal charcoal, and lowness of temperature 

 at which it is evaporated, and rapidity of evaporation. The methods 

 of securing these conditions will be described further on. 



There is one variety of glucose which is made for confectioners' 

 use, which is much thicker and denser than that just described. Its 

 specific gravity may reach 1-440, but it has no tendency to become 

 hard and solid, like the so-called grape-sugar. 



The grape-sugar made from corn-starch, when well made, is pure 

 white in color when first made, but has a tendency to assume a yellow- 

 ish tint when old. It is hard and brittle, does not usually take on a 

 visible crystalline structure, and is less soluble in water than cane-sugar. 

 Perhaps it would be more accurate to say that it dissolves more slowly, 

 since both cane- and grape-sugar dissolve in all proportions in hot water. 

 I have found its specific gravity to be as high as 1 -6. It is much less 

 sweet to the taste than glucose, and a faint bitter after-taste is to be 

 perceived. 



Uses of Glucose and Gkape-Sugae. Glucose is used chiefly for 

 the manufacture of table-sirups, candies, as food for bees, for brewing, 

 and for artificial hone^y. 



It is impossible at present to get any reliable statistics concerning 

 the amount of glucose used in beer-making. The brewers themselves 

 try to keep its use a secret, since it is quite common to proclaim that 

 beer is made from barley and hops alone, although this is rarely the 

 case. Dealers and manufacturers are likewise reticent when approached 

 on this subject, since it is but natural for them to wish to protect the 

 interests of their patrons. We shall not go far wrong, however, when 



* See paper read by the author at the Boston meeting of the American Association 

 for the Advancement of Science. 



