TESTS FOR SUGAR. 267 



Recently the presence of peptone-producing ferments in the saliva has been 

 discovered, but they are perhaps merely absorbed from the intestine and again 

 excreted in the saliva (as occurs in the urine). 



TESTS FOR SUGAR. 



Trammer's test, like several others, depends upon the fact that sugar in hot 

 alkaline solution acts as a reducing agent; here a metallic oxid is transformed 

 into a suboxid. To one-half as much potassium-hydrate or sodium-hydrate 

 solution, of a specific gravity of 1.25, is added the fluid to be tested. Then a 

 weak solution of cupric sulphate is added drop by drop until the bluish precipitate 

 that appears at first and consists of cupric oxid, is again dissolved by agitation. 

 If sugar is present, the precipitate again forms a deep-blue solution after 

 agitation. If heat is applied gradually almost up to the boiling-point a yellowish 

 or reddish cloud is formed from above, which is finally precipitated as brownish- 

 red cuprous oxid or as yellowish-red cupric oxid: 2CuO O = Cu 2 O. 



Cuprous oxyhydrate is dissolved also by other organic substances, though only 

 certain sugars maltose, grape-sugar, fruit-sugar and milk-sugar, but not cane- 

 sugar cause final reduction. Fluids previously turbid must be filtered and possibly 

 treated with basic lead acetate. In the latter event the excess of lead is precipi- 

 tated by sodium phosphate; then filtration is practised. When the amount of 

 sugar is exceedingly small, concentration of the fluid over the water-bath may be 

 necessary. If small amounts of sugar, less than 0:5 per cent., are present, to- 

 gether with ammonia, uric acid, and kreatinin, instead of a yellow precipitate, 

 merely a yellow solution of cuprous oxid may result. The addition of an excess 

 of cupric sulphate, which should always be avoided, causes confusion by the 

 precipitation of black cupric oxid. 



Bottger's test is made with an alkaline solution of bismuth oxid, best prepared 

 according to Nylander as follows: Bismuth subnitrate 2 grams, sodio-potassium 

 tartrate 4 grams, and sodium hydrate (8 per cent.) 100 grams. One cu. cm. of 

 this mixture is added to 10 cu. cm. of the fluid to be tested. Upon boiling for 

 several minutes the sugar present causes reduction to metallic bismuth, with the 

 formation of a black precipitate. 



Moore's and Heller's test: Sufficient sodium or potassium hydrate is added 

 to the fluid to give it a strongly alkaline reaction. On boiling, a yellowish, brownish 

 or brownish-black color results from the formation of humus-substances. If, 

 after cooling, one drop of concentrated sulphuric acid is added, the odor of burnt 

 sugar (caramel) and formic acid develops. 



Mulder's and Neubauer's test: If a solution of indigo-carmin, made alkaline 

 by sodium carbonate, is added to a fluid containing sugar until a pale-blue color 

 is produced, and heat is applied, the color becomes successively green, purple, 

 reel and yellow. Agitated with atmospheric air the fluid again acquires the 

 blue color. 



Molisch's tests: To cu. cm. of the fluid to be tested, 2 drops of a 17 per cent, 

 alcoholic solution of a-naphthol or of a solution of thymol are added ; with dilute 

 solutions of sugar a small quantity of solid a-naphthol may be used instead of 

 the solution. Then i or 2 cu. cm. of concentrated sulphuric acid are added 

 and the fluid is rapidly shaken. In the presence of sugar the a-naphthol mix- 

 ture becomes deep violet in color, the thymol-solution deep red. Subsequent 

 dilution with water causes a precipitate of the same color, which is insoluble 

 in concentrated hydrochloric acid. Albumin, casein and peptone also yield 

 this reaction, but the precipitate appearing upon the addition of water is solubl< 

 in concentrated hydrochloric acid. 



Phenylhydrazin test: To 7 cu. cm. of the fluid in a test-tube a small amoun 

 of phenylhydrazin chlorid (0.2) and also of sodium acetate (0.3) are added. Heat 

 is applied until solution takes place, water being added if necessary, 

 kept in boiling water for an hour. The contents are then poured into a conical 

 glass, at the bottom of which characteristic yellow, microscopical tufts of fine, 

 long needles of phenylglucosazone are found, which are almost insoluble in water; 

 while maltose produces an analogous substance, phenylmaltosazone, which is 

 soluble in hot water. 



From all fluids to be tested for sugar, any albumin present should first 

 removed; from the urine by boiling, after slight acidulation with acetic acid 

 from the blood, by the method described on page 73; the alcohol is driven 

 heat. 



