APPENDIX 489 



To distinguish between Dextrose, Maltose, and Lactose. 



(1) Prepare osazone crystals (p. 417) and examine under the 



microscope dextrosazone gives long thin needles ; 

 maltosazone, short thick needles; lactosazone, needles 

 of varying length and thickness (Fig. 266). 



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



this with ease ; lactose and maltose not so readily. 



II. For Proteids. 



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



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

 proteose or peptone. 



2. Apply Millon's and the Xantho-proteic tests. 



(a) A well-marked reaction indicates proteids of Kossel's 3rd 

 and 4th groups, (b) A faint reaction (combined with a 

 distinct biuret, and the absence of coagulation on boiling) 

 points to gelatine (2nd group). (Confirm by seeing if 

 the solution gelatinises on cooling). 



If the Biuret Test gives a Violet Colouration, 



A. Add a drop or so of dilute acetic acid and boil. A 



coagulum points to native proteids. To ascertain which 

 of these is present (i.e. albumin or globulin), half saturate 

 some of the solution with (NH 4 ) 2 S0 4 . A precipitate 

 indicates globulin; filter; if the filtrate still gives a 

 coagulum on boiling, albumin is present (for details, see 

 p. 176). 



B. Carefully neutralise some of the solution. A precipitate 



may be : 



excess 



3. Nucleo albumin-original reciitate does not dis . 



4. Mudn-al fluid * . 



moderate excess of acid. 



To distinguish between Nucleo Albumin and Mucin. This is 

 possible only when a large amount of these bodies is present. 

 The acetic acid precipitate is collected on a filter paper, washed 

 with acidulated water, and divided into two portions a and b. 

 (a) Boil with 20 per cent. HC1 for It) minutes ; cool ; 

 neutralise; apply Trommer's test. A positive reaction 

 points to mucin. 



