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. 



(b) Compounds of monosaccharides with alcohols, 

 phenols, aldehydes, and organic acids are called gluco- 

 sides. By boiling with acids or by the action of many 

 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, 

 galactose, 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- 

 trose) 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 and has 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 



