TESTS FOR SUGARS. 173 



Bleaching Gums. — Picciotto describes a process for de- 

 colorizing Arabian gums (Lond. Journ. 1849), by dissolving 

 them in a strong solution of sulphurous acid, distilling off 

 part of the acid, and precipitating the balance by carbonate 

 of baryta, and, after filtering, evaporating to dryness. Or, 

 the gums may be decolorized and cleansed by adding hy- 

 drated alumina to their solution, filtering and evaporating. 

 If the gums are to be used for medicinal or alimentary 

 purposes, the use of baryta is highly objectionable, and in- 

 deed for most purposes the decolorization is a matter of minor 

 importance. 



2. Sugar. — When starch is acted upon by sulphuric acid or 

 diastase in water, it is converted into a sugar, called starch- 

 sugar, which seems to be identical with grape-sugar. Cane- 

 sugar treated with acids is resolved into the same kind ; but we 

 have not as yet succeeded in producing cane-sugar from grape 

 or starch-sugar. There is room for extended observation in 

 the changes suffered by the sugars, both in relation to science 

 and to practice. 



Tests for Sugars. — G. Reich thuo distinguishes between dif- 

 ferent kinds of sugar. (Gewerbvereinsbl. d. Provinz Preussen, 

 1846.) If a hot concentrated solution of bichromate of po- 

 tassa be added to molasses (cane-sugar molasses), in a test-tube, 

 and heated to boiling by a spirit lamp, an energetic action 

 takes place between them after removing the flame, until the 

 liquid has assumed a beautiful green color from oxide of 

 chrome, which is rendered more distinct by dilution with water. 

 Starch-molasses produces no change whatever, under similar 

 circumstances. Even when common molasses is mixed with 

 \—^ starch-molasses, no change is produced, or if it be, it does 

 not exhibit the fine green color of pure cane-molasses. A solu- 

 tion of the bichromate is not acted on by syrup (a solution) of 

 cane-sugar, and hence molasses-sugar shows itself distinct in 

 kind from the two others. • 



A solution of nitrate of cobalt is, according to Reich, a good 

 mean of distinguishing cane and grape sugars. A strong 

 solution of cane-sugar, treated with fused potassa, heated to 

 p2 



