loo THE CARBOHYDRATES 



Mangham * and others have obtained excellent results by 

 the use of the osazone test for microscopic work ; if properly 

 performed, it is much more satisfactory than any other, and 

 has the advantage of being a very delicate test for some sugars. 

 For example, a -015 per cent solution of glucose will give a 

 definite reaction. The main disadvantage of the method is in 

 its comparative slowness. 



Two solutions are required : — 



{a) I gram of phenylhydrazine hydrochloride dissolved in 

 10 grams of glycerol. 



{b) I gram of sodium acetate dissolved in 10 grams of 

 glycerol. 



If necessary the solution of these substances may be 

 hastened by means of heat, and before use the solutions 

 should be filtered. 



Glycerol is used because its penetrative power is greater 

 than that of water, and also because it will not evaporate and 

 deposit crystals of the substances used. 



For use, one drop of each fluid is placed on a glass slip 

 and mixed thoroughly. The section, which must be more 

 than one cell in thickness, is laid in the mixture and covered 

 with a cover glass. The preparation is heated on a hot 

 water oven for about half an hour, and is then allowed to 

 cool ; the osazone crystals will form in varying degrees of 

 rapidity. 



In order that familiarity with the method may be gained, 

 the reagents may be mixed on the slip with drops of sugar 

 solution of different concentrations heated for varying periods 

 and examined periodically after cooling. 



Maltose gives an osazone characterized by dense rosettes of 

 lemon-yellow crystals, which are broader and larger than those 

 obtained with dextrose and levulose. 



Dextrose and levulose may be distinguished by the fact 

 that methylphenylhydrazine gives a crystalline osazone with 

 levulose and not with dextrose. 



* Mangham: "New PhytoL," 1911, lO, 160; "Ann. Bot.," 1915. 

 29, 360. 



