470 PRACTICAL PHYSIOLOGY 



The following Chemical Tests should now be applied to Suitable 



Quantities of the Solution. 

 I. For Carbohydrates. 



1. Apply Trommer's test. 



A. Positive indicates monosaccharides, lactose, or maltose. 



B. Negative, but complete solution of cupric hydrate obtained 



on adding caustic alkalie, indicates cane sugar. Confirm 

 for this by boiling some of the solution with a mineral 

 acid for a minute or so, and applying Trommer's test to 

 the product reduction indicates cane sugar. The 

 original solution will also taste sweet. 



C. Negative, and no solution of cupric hydrate. Absence of 



monosaccharides and disaccharides. 



2. Add Iodine Solution. 



(a) a blue colour which disappears on heating, and returns on 



cooling indicates starch. 



(b) a port-wine colour which disappears on heating, and 



returns on cooling indicates dextrin or glycogen. Confirm 

 for polysaccharides by heating some of the original fluid 

 for about fifteen minutes with a mineral acid, and testing 

 for sugar in the hydrolysed fluid. 



To distinguish between Starch, Glycogen, and Dextrin. Shake 

 up some of the original powder with cold water and filter. By 

 this treatment glycogen and dextrin will dissolve, starch will 

 not. Wash the filter paper thoroughly with water, then add 

 a drop of Iodine solution a blue stain indicates starch. Add 

 Iodine solution to the filtrate a red colour indicates dextrin 

 or glycogen ; if the former body be present the filtrate is 

 clear, opalescent if the latter. 



To distinguish between Dextrose, Maltose, and Lactose. 



(1) Prepare osazone crystals and examine under the micro- 



scope dextrosazone gives long thin needles ; maltosazone, 

 short thick needles ; lactosazone, needles of varying 

 length and thickness. 



(2) Barfoed's reaction may also be tried. Dextrose reduces 



this with ease ; lactose and maltose not so readily. 



II. For Proteins. 



1. Apply the Biuret reaction (a) A violet colour indicates 

 native proteins or albuminoids; (b) a rose pink colour, 

 proteose or peptone. 



