86 LABORATORY WORK IN PHYSIOLOGICAL CHEMISTRY. 



important factor (volume), the consideration of which is 

 indispensable, especially when extreme values are met with. 

 It is unnecessary to add that the urine should be ex- 

 amined as fresh as possible, or, in the event of this not being 

 feasible, the fluid must be well supplied with antiseptic agents 

 such as powdered thymol, chloroform, NaF, etc. 



Physical Properties. 



The following comprise the important physical properties 

 of urine to be specially noted in an examination: 



Color. Aromatic alcohols, salol and allied compounds 

 cause the urine to become brown upon standing. Rhubarb 

 and senna impart a reddish color, which, if the urine is 

 alkaline, may be confounded with the appearance of blood. 

 The ingestion of quinine in large quantities gives to the 

 urine a greenish opalescence and methylene blue is followed 

 by the appearance of urine of a decided bluish-green tinge. 



It is usual to refer to Vogel's color chart, but unless the 

 color is other than that of some shade of yellow, little can be 

 deduced from the determination of this property. 



Odor. Normal (urinous), ammoniacal, or that peculiar to 

 some substance not normally present, such as acetone, 

 methyl mercaptan, etc. 



Transparency. Clear or cloudy. Usually upon standing, 

 a cloud of mucous-like substance separates, suspending itself 

 in some part 'of the urine. 



Reaction. Acid, neutral, or alkaline. 



As is true of any acid solution, the acidity of the urine 

 is due to the presence of dissociated hydrogen atoms (ions). 

 It is usually assumed that these acid ions are derived from 

 the acid salts, such as H 2 NaP0 4 or HNa-jPC^ (mineral acidity), 

 but in all probability the H ions of the organic acids in the 

 urine also add a not inconsiderable part to the. total acidity. 



