312 PHYSIOLOGICAL CHEMISTRY. 



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 with 

 urine containing albumin this must be removed, by boiling and fil- 

 tering, before applying the test, since with albumin a similar change 

 of color is produced (bismuth sulphide). 



(/) Nylander's Test (Ahnen's Test). To 5 c.c. of urine 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 mixture will darken 

 if reducing sugar is present and upon standing for a fe\v 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. 

 Dextrose when present to the extent of 0.08 per cent may be de- 

 tected by this reaction. It is claimed by Bechold that Nylander's 

 and Boettger's tests give a negative reaction with solutions con- 

 taining sugar when mercuric chloride or chloroform is present. 

 Other observers have failed to verify the inhibitory action of the 

 mercuric chloride and have shown that the inhibitory influence of 

 chloroform may be overcome by raising the temperature of the 

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

 making the test. . 



Urines rich in indican, uroerythrin or hceniatoporphyrin, as well 

 as urines excreted after the ingestion of large amounts of certain 

 medicinal substances, may give a darkening of Nylander's reagent 

 similar to that of a true sugar reaction. 



According to Rustin and Otto the addition of PtCl 4 increases the 

 delicacy of Nylander's reaction. They claim that this procedure 

 causes the sugar to be converted quantitatively. No quantitative 

 method has yet been devised, however, based upon this principle. 



A positive Nylander or Boettger test is probably due to the fol- 

 lowing reactions: 



(a) Bi(OH) 2 N0 3 + KOH Bi(OH) 3 + KN0 3 . 



(b) 2Bi(OH) 3 -30 = Bi 2 -f3H 2 O. 



4. Fermentation Test. Rub up in a mortar about 15 c.c. 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 10 per cent potassium hydroxide 

 solution. The reagent is then cooled and filtered. 



2 Hammarsten suggests that the solution be boiled for 2-5 minutes (accord- 

 ing to the sugar content) over a free flame and the tube then permitted to 

 stand five minutes before drawing conclusions. 



