CARBOHYDRATES 2Q 



This test is positive with such sugars as give other reduction tests, 

 e.g., glucose, fructose, lactose, maltose, arabinose, etc. If the reducing 

 sugar be present in aqueous solution a slight reduction may be obtained 

 with i mg. of glucose. If the reagent be made strongly alkaline, it 

 ceases to be specific for reducing sugars and chemically allied sub- 

 stances and is reduced by other organic substances, e.g., creatinine. 



It is claimed that this test is free from fallacies inherent in Fehling's 

 test as the result of the reducing action of uric acid and creatinine. 



The test is more sensitive than the Fehling's or Nylander's reac- 

 tions, and is particularly suitable for the examination of urines in which 

 the amount of sugar present exceeds the normal amount only slightly. 



(e) Bismuth Reduction Test (Boettger). To 5 c.c. of sugar solution in a test-tube 

 add i c.c. of KOH or NaOH and a very small amount of bismuth subnitrate, and 

 boil. The solution will gradually darken and finally assume a black color due to 

 reduced bismuth. If the test is made on urine containing albumin this must be 

 removed, by boiling and filtering, before applying the test, since with albumin a 

 similar change of color is produced (bismuth sulphide). 



(f) Bismuth Reduction Test (Nylander). To 5 c.c. of sugar solution in a test- 

 tube add one-tenth its volume of Nylander's reagent 1 and heat for five minutes 

 in a boiling water-bath. 2 The solution will darken if reducing sugar is present, 

 and upon standing for a few moments a black color will appear. 



This color is due to the precipitation of bismuth. If the test is made 

 on urine containing albumin this must be removed, by boiling and 

 filtering, before applying the test, since with albumin a similar change of 

 color is produced. Glucose when present to the extent of 0.08 per cent 

 may be easily detected by this reaction (Rabe 3 claims that o.oi per cent 

 sugar may be so detected). Uric acid and creatinine which interfere 

 with the Fehling's test do not interfere with the Nylander test. It 

 is claimed by Bechold that the bismuth reduction tests give a nega- 

 tive reaction with solutions containing sugar when mercuric chloride or 

 chloroform is present. Other observers 4 have failed to verify the 

 inhibitory action of mercuric chloride and have shown that the in- 

 hibitory influence of chloroform may be overcome by raising the tem- 

 perature of the urine to the boiling-point for a period of five minutes 

 previous to making the test. Urines rich in indican, urochrome, uroery- 

 thrin or hematoporphyrin, as well as urines excreted after the ingestion of 

 large amounts of certain medicinal substances, may give a darkening of 



1 Nylander's reagent is prepared by digesting 2 grams of bismuth subnitrate and 4 grams 

 of Rochelle salt in 100 c.c. of a lo'per cent potassium hydroxide solution. The reagent is 

 then cooled and filtered. 



2 Hammarsten suggests that the mixture should be boiled 2-5 minutes (according to the 

 sugar content) over a free flame and the tube then permitted to stand 5 minutes before 

 drawing conclusions. 



3 Rabe: Apoth. Ztg., 29, 554, 1914. 



4 Rehf uss and Hawk: Journal of Biological Chemistry; 7, 267, 1910; also Zeidlitz: 

 Upsala Lakareforen Fork., N. F., n, 1906. 



