n6 



PRACTICAL PHYSIOLOGY. 



[XVII. 



flow tube is filled with the SS. Note the height of the fluid 

 in the burette. Heat the urine in the beaker to about 80 C. 

 Drop in the SS. ("Standard Solution ") of uranium acetate from 

 the burette. Mix thoroughly. Test a drop of the mixture from 

 time to time, until a drop gives a faint brown colour 

 when mixed with a drop of potassium ferrocyanide. 

 Do this on a white plate. 



(e.) Boil the mixture and test again. If necessary, 

 add a few more drops of the SS., until the brown 

 colour reappears on testing with the indicator. 

 [Paper may be dipped in the indicator solution and 

 tested with a drop of the mixture.] Read off the 

 number of cc. used. 



Example. Suppose 17 cc. of the SS. are required to 

 precipitate the phosphates in 50 cc. of urine ; as i cc. of 

 SS. =.005 gram of phosphoric acid, then .005x17 = .085 

 gram of phosphoric acid in 50 cc. of urine. Suppose the 

 patient passed 1250 cc. of urine in twenty-four hours, then 



1250 x. 085 

 50 : 1250 : : .085 : x = 2. 12 grams of phosphoric in 



twenty-four hours. 



12. Reading off the Burette. In the case of the 

 burette being filled with a watery fluid, note that the 

 upper surface of the water is concave. Always bring 

 the eye to the level of the same horizontal plane as 

 the bottom of the meniscus curve. Fig. 58 shows 

 how different readings may be obtained if the eye is 

 placed at different levels, A, B, C. 



FIG. 



Erdmami's Float. 13. Erdmann's Float (fig. 59) consists of a glass vessel 

 loaded with mercury, so that it will float vertically. It is 

 used to facilitate the reading off of the burette. It has a horizontal line 

 engraved round its middle, and must be of such a width as to allow it just 

 to float freely in the burette. Read off the mark on the burette which 

 coincides with the ring on the Hoat. 



14. Carbonates and bicarbonates of the alkalies are generally present in 

 alkaline urine,and are most abundant in the urine of herbivora and vegetarians. 

 They are derived from the oxidation of the organic vegetable acids. Car- 

 bonate of lime is not normally present in human urine, though it is sometimes 

 found as a urinary deposit. 



15. The Lime, Magnesia, Iron, and other inorganic urinary constituents are 

 comparatively unimportant, and have no known clinical significance. 



