412 PHYSIOLOGICAL CHEMISTRY. 



reagent may be used without disadvantage. In a urine poor in 

 sugar we must only use 1 c. c. of the reagent for every 10 c. c. of 

 the urine. 



This test shows the presence of 1-0. 5 p. m. sugar in the urine. 

 The sources of error which interfere in TROMMER'S test, such as the 

 presence of uric acid and creatinin, entirely disappear in this 

 test. The bismuth test is, besides this, more easily performed, and 

 it is therefore to be recommended to the physician. Small amounts 

 of albumen do not interfere with this test ; large amounts may give 

 rise to an error by forming bismuth sulphide, and therefore must 

 be removed by coagulation. 



In using this method it must not be overlooked that it is, like 

 TROMMER'S test, a reduction test, and it consequently may show, 

 besides sugar, certain other reducing substances. Such bodies are 

 certain coupled glycuronic acids which may appear in the urine. 

 SALKOWSKI obtained a bluish-black precipitate with this reagent in 

 a urine after the use of rhubarb, and black precipitates have been 

 obtained with the bismuth test after the use of turpentine and cer- 

 tain other medicines. From this it follows that we should, espe- 

 cially when the reduction is not very great, never be satisfied with 

 this test alone. As a control at least one of the following tests 

 must be performed. Among these the fermentation test is of 

 special value. 



Fermentation Test. On using this test we must proceed in vari- 

 ous ways, according as the bismuth test gives small or large results. 

 If a rather strong reduction is obtained, the urine may be treated 

 with yeast and the presence of sugar determined by the generation 

 of carbon dioxide. In this case the acid urine, or otherwise faintly 

 acidified with tartaric acid, is treated with yeast which has previ- 

 ously been washed by decantation with water. Pour this urine to 

 which the yeast has been added into a SCHROTTER'S gas-burette, or 

 glass tube with the open end ground, close with the thumb, and 

 open under the surface of mercury contained in a dish. As the 

 fermentation proceeds, the carbon dioxide collects in the upper 

 part of the tube/while a corresponding quantity of liquid is expelled 

 below. As a control in this case, two other similar tests must be 

 made, one with normal urine and yeast to learn the amount of gas 

 usually developed, and the other with a sugar solution and yeast to 

 determine the activity of the yeast. 



If, on the contrary, we find only a faint reduction with the bis- 

 muth test, no positive conclusion can be drawn from the absence of 

 any carbon dioxide or the appearance of a very insignificant 

 amount. In this case proceed in the following way : Treat the 

 acid urine, or the urine which has been faintly acidified with tar- 

 taric acid, with yeast whose activity has been tested by a special 

 test on a sugar solution, and allow it to stand 24-48 hours at the 



