HANDBOOK FOR BIO-CHEMICAL LABORATORY. 5 



gradually add 500 grms. powdered cane-sugar, stirring all 

 the while and taking care that the temperature does not 

 rise above 50 C. After two hours the sugar will have dis- 

 solved and will be inverted into dextrose and laevulose ; allow 

 it to cool, and place it in a cold place until crystallization com- 

 mences, which occurs in from six to eight days. The crystal- 

 lization may be facilitated by constant stirring. If pure anhy- 

 drous crystals of glucose are at hand, add a few grammes to 

 the cold solution and stir well. In this case the crystalliza- 

 tion will begin in a few hours, and is complete in 36 hours. 

 The crystals thus obtained are well drained, then washed free 

 from HC1 by 90$ alcohol, then with absolute alcohol, and 

 now dried at a moderate heat. To completely purify these 

 crystals boil them for five to ten minutes with pure methyl 

 alcohol* (sp. gr. 0.810 at 20 C.), filter, quickly cool, and the 

 glucose crystals will separate out. (Soxhlet). 



Properties. Dextrose (glucose, grape sugar) is readily sol- 

 uble in water, sparingly soluble in alcohol, and insoluble in 

 ether. It crystallizes from an aqueous solution in white 

 spheroidal masses, and from alcohol in transparent anhydrous 

 prisms. Its solutions rotate the ray of polarized light to the 

 right : (a) D -f- 52.6. In alkaline solutions dextrose 

 reduces salts of silver, bismuth, mercury, and copper. Under 

 the influence of yeast it is converted into alcohol and carbon 

 dioxide. It may also undergo lactic-acid fermentation under 

 the influence of certain bacterial growths. With a mixture 

 of 2 parts phenyl-hydrazine hydrochloride and 3 parts sodium 

 acetate a watery solution of glucose gives, when heated on 

 the water-bath, a precipitate of fine yellow needles (phenyl 

 glucosazon, C 18 H 21 N 4 4 ), melting at 204-205 C. 



* The purest methyl alcohol is mixed withjabout 20# water, and about 

 four-fifths distilled off on the water-bath. This distillate has, as a 

 rule, the above specific gravity, and is immediately used. 



