URINE AND ITS CONSTITUENTS. 731 



ogous to the formation of the soluble scale compounds of iron, where the pre- 

 cipitation of ferric hydroxide is also prevented by tartaric or other organic acids. 



The test is made by heating in a test-tube 10 c.c. of Folding's solu- 

 tion which has been diluted with 2 to 5 volumes of water and add- 

 ing drop by drop the suspected urine ; if the latter contains larger 

 quantities of sugar, a yellow or red precipitate of cuprous hydroxide 

 and oxide will be produced very readily ; if but small quantities are 

 present, the reaction will appear only on standing for some time. 



Haines' test is a modification of Fehling's test. The reagent is as 

 follows : " Dissolve 30 grains of cupric sulphate in \ ounce of water, 

 add \ ounce of glycerin and then 5 fluidounces of liquor potassse." 

 The advantage of the reagent is that it is very stable. It should be 

 used by boiling about 1 drachm in a test-tube, adding 8 to 10 drops 

 of the suspected urine, and again bringing to a boil. In the presence 

 of sugar a precipitate of cuprous oxide is thrown down. 



3. Botgcr's bismuth test consists in adding to a mixture of equal 

 volumes of urine and potassium (or sodium) hydroxide solution a few 

 grains of subnitrate of bismuth and boiling for half a minute. If 

 sugar be present, a gray or dark -brown, finally black, precipitate of 

 bismuthous oxide, Bi 2 O 2 , or of metallic bismuth is formed. If but 

 very little sugar is present, the undecomposed excess of bismuthic 

 nitrate (or bismuthic hydroxide) mixes with the metallic bismuth, 

 imparting to it a gray color ; the test should then be repeated with a 

 smaller amount of the bismuth salt. (Plate VIII., 6.) 



The above test may be advantageously modified by using a bismuth 

 solution instead of the powder. The solution known as Nylander's 

 reagent is made by dissolving 2 grammes of bismuth subnitrate, 4 

 grammes of Rochelle salt, and 10 grammes of sodium hydroxide in 

 90 c.c. of water, and filtering. One-half c.c. of this solution is heated 

 with about 5 c.c. of urine, when, in the presence of sugar, a brown 

 or black precipitate will form after a few minutes 7 boiling. 



If the urine contains hydrogen disulphide (sometimes produced by decom- 

 position of certain urinary constituents), black bismuth sulphide will be formed, 

 which may be mistaken for metallic bismuth ; albumin itself may be the cause 

 of the formation of alkaline sulphides : the previous complete separation of 

 albumin is therefore indispensable. 



4. Moore's or Heller's test is made by heating urine with about 

 one-fourth its volume of solution of potassium hydroxide. In the 

 presence of sugar the color of the mixture will deepen to a dark yel- 

 low or brown, and the depth of color is a fair indication of the quan- 



