230 ORGANIC AGRICULTURAL CHEMISTRY 



Benedict's Modified Fehling's Solution 



Copper sulphate 17.3 grams 



Sodium citrate i73-o grams 



Sodium carbonate loo.o grams 



(anhydrous) 



Water to make looo.o c.c. 



Glucose is also sometimes tested for clinically by subjecting the 

 urine to the action of yeast and measuring the carbon dioxide 

 evolved. 



Albumin. — The presence of albumin in urine indicates a 

 pathological condition termed albuminuria or nephritis. Brighfs 

 disease is a particular form of the condition. The testing of 

 urine for albumin, as for glucose, is therefore an important 

 clinical operation. The test usually made depends upon the 

 property of albumins to form insoluble compounds with mineral 

 acids. It is known as Heller^s ring test and is described in the 

 experiment study. 



General Properties 



Human urine is a clear straw-colored liquid, becoming often 

 considerably darker if of high specific gravity. The amount 

 varies greatly with the amount of water that is drunk, but 

 averages from 1000 to 1500 c.c. in twenty-four hours. It fre- 

 quently becomes cloudy on standing, due to the precipitation 

 of phosphates, especially if the urine is alkaline in reaction, which 

 often occurs after a hearty meal. Normally urine is slightly 

 acid in reaction. The specific gravity of normal urine is 1.015 

 to 1.025. This may be greatly changed by large variations in 

 drinking water. Excessive drinking of water may so dilute the 

 urine as to lower its specific gravity to 1.003 ^^^ cutting down 

 the supply of water may raise it to 1.04. Diabetic urine has a 

 high specific gravity, but this alone does not indicate the disease 

 unless the amount of water is considered. 



