20 HUMAN PHYSIOLOGY 



3. Moore' s test: Boiled with alkali, the sugar is oxidized 

 and assumes a brown color. 



4. In an acetic acid solution, monosaccharides, like alde- 

 hydes and ketones, unite with phenylhydrazine, forming 

 hydrazones, water being set free. This, by the further 

 taking up of a molecule of phenylhydrazine and the separa- 

 tion of the water and t'he setting free of hydrogen, forms 

 phenylosazone. These compounds have characteristic crys- 

 tals and melting-points which may aid in the detection of 

 sugar. 



5. Compounds of monosaccharides : 



(a) Compounds of monosaccharides with bases are 

 called saccharates. Lead saccharates are insoluble in 

 ammonia and are therefore used for the precipitation 

 of sugar. 



(/;) Compounds of monosaccharides with alcohols, 

 phenols, aldehydes, and organic acids are called gluco- 

 sides. By boiling with acids or by the action of main- 

 ferments, they are easily decomposed, under the 

 assumption of water, into their components. 



6. The yeast-cell splits up nearly all the monosaccharides 

 into alcohol and carbonic acid (alcoholic fermentation) ; the 

 bacterium lactis splits up most of them into lactic acid (lactic- 

 acid fermentation). 



Among the monosaccharides are grape-sugar, fructose, 

 galactosc, mannose. Grape-sugar is found in the animal 

 body; the others are of importance as foods. 



Grape-sugar (glucose in a more restricted sense, or dex- 

 Jrose) is the aldehyde of sorbit, a hexatomic alcohol found 

 in the service-berry. 



Grape-sugar is dextrorotatory (hence called dextrose), 

 reduces and forms, with phenylhydrazone, phenylglucosa- 

 zone, which crystallizes in branches having the melting- 

 point at 204 C. It is capable of alcoholic fermentation, 

 Its oxidation forms first gluconic acid 'monobasic) and then 

 saccharic acid (dibasic). 



Grape-sugar is found in sweet fruits, in honey and, in 



