178 PHYSIOLOGICAL CHEMISTRY 



even 10 liters per day and greater volumes have been reported, 

 Such a condition is known as polyuria. 



Color, Transparency. The color of normal urine ranges from 

 a pale straw color to a dark brown. Ordinarily it is amber. The 

 color is due to the presence of pigments, urochrome and uro- 

 bilin being of greatest importance. Uroerythrin may give normal 

 urine or its sediments a reddish color. Dilute urines of large 

 volume usually are pale in color, concentrated urines usually 

 darker. The reaction of the specimen also affects the color, as 

 acid urines are usually darker, alkaline urines lighter. 



Various pathological colorings may occur, thus blood pig- 

 ment or its derivatives may cause a red or brown ; bile pigments 

 give the urine a dark brown, greenish, or greenish black color. In 

 a condition known as alcaptonuria the urine turns dark on stand- 

 ing. It should be borne in mind that various drugs will color 

 the urine, such as senna (yellow), tar preparations, salol, etc. 

 (brown). Also madder, beets, or the analine dyes used in cheap 

 candies may result in abnormal colorations. 



The transparency of normal urine varies greatly. Fresh acid 

 urine usually is clear or fairly so. If concentrated, it may be 

 cloudy from a precipitate of urates or uric acid. This precipi- 

 tate will dissolve on warming. On standing, a slight sediment 

 usually settles out. This consists of various cells or cell debris, 

 urates, uric acid and some other substances. 



If the specimen is alkaline, it usually is cloudy from precipi- 

 tated phosphates or carbonates of the alkaline earths. This 

 cloudiness does not disappear on warming, but does on acidi- 

 fying. 



Pathological urine may be cloudy from mucin, epithelial cells, 

 pus, blood, bacteria, etc. 



To clear a cloudy specimen filtering often is sufficient. If 

 the urine is alkaline, the addition of acetic acid may cause 

 clearing. 



Decolorizing may be brought about by adding charcoal, or 

 permanganate or in other ways. The method chosen should not 

 interfere with the analysis to be undertaken however. 



