CELL-CONTENTS AND CELL-WALLS. 55 



when a yellow crystalline mass of phenyl glucosazone should be 

 deposited. Cool ; filter off the crystals, and examine them with 

 the microscope. They are needle-like, and arranged in feather-like 

 tufts or in rosettes. 



(g) Molisch Test. To some sugar solution add a drop or two 

 of a-naphthol solution, then run into the bottom of the tube a little 

 (about 2 c.c. ) strong sulphuric acid. A violet ring appears at the 

 junction of the two liquids, either at once or in a short time. This 

 reaction is chiefly of importance in proving the presence of a carbo- 

 hydrate radicle in the molecule of proteins ( 41, g}. 



64. Reactions of Sucrose. Dissolve pure cane sugar 

 in water, and note that (1) it does not give a brown colour 

 with potash ; (2) it does not reduce alkaline solutions of 

 metallic oxides, hence no precipitate is given with the 

 Fehling, Barfoed, and Trommer tests, nor is silver thrown 

 down ; (3) it gives no osazone with phenylhydrazine and 

 acetic acid. 



If, however, cane sugar is boiled for a long time in 

 water, or for a shorter time in dilute mineral (e.g. sul- 

 phuric) acid, it is converted into a mixture of the mono- 

 saccharides glucose and fructose, and the solution on 

 being neutralised gives reduction of copper oxide from 

 Fehling, etc. 



65. Reactions of Maltose. Note that maltose agrees 

 with glucose in (1) being coloured brown when heated 

 with soda or potash ; (2) reducing metallic oxides in alka- 

 line solution ; (3) forming an osazone with phenylhydrazine. 

 It does not, however, reduce Barfoed's solution. With the 

 phenylhydrazine test, maltosazone is not deposited while 

 the solution is hot, but only when after being heated for 

 half an hour the solution is allowed to cool ; the crystals 

 are shorter and thicker than those of glucosazone. 



66. Microchemical Tests for Sugar.. Fehling's 

 test is readily applied to tissues in which the presence of 

 sugar is to be detected. Eather thick sections should be 

 cut, so that a good many of the cells will remain intact. 

 Soak the sections in Fehling in a watch-glass for a few 

 minutes, rinse them quickly in water, and heat the slide 



