746 PHYSTOLOGICAL CHEMISTRY. 



sharp odor. On evaporation of its solution in ammonia it separates 

 in characteristic six-sided plates. 



C. Material which does not burn may consist of calcium car- 

 bonate, calcium oxalate, or phosphates. Calcium carbonate shows 

 effervescence with all acids, and the solution, after being neutralized, 

 is precipitated by ammonium oxalate. Calcium oxalate does not 

 effervesce with hydrochloric acid directly, but does so after being 

 heated, when carbonate is formed and is tested for as such. The 

 presence of phosphates is indicated by the presence of a yellow pre- 

 cipitate, produced in the solution in nitric acid by ammonium molyb- 

 date. When the phosphates, on heating with caustic potash, evolve 

 ammonia gas, magnesium ammonium phosphate is present ; when the 

 test is negative the calculus consists of calcium phosphate, which can 

 be verified by dissolving the powder in hydrochloric acid, neutral- 

 izing with ammonia, redissolving the precipitate in acetic acid, and 

 adding ammonium oxalate, when a white precipitate is formed. 



Most common are calculi of uric acid ; often met with are those of 

 urates, phosphates, and oxalates ; rarely, however, those of xanthine, 

 cystine, fibrin, and urostealith. 



QUESTIONS. What is urine, where and by what process is it formed in the 

 animal body, and what is its function? Mention the general physical and 

 chemical properties of urine. Give the composition of human urine, and state 

 by what conditions the composition is influenced. State the composition and 

 properties of urea. By what process is urea formed in the animal body, and 

 how can it be obtained artificially ? Describe a process by which urea may be 

 estimated quantitatively in urine. In what forms is uric acid found in urine, 

 and what are its properties? Describe the murexide test. How can uric acid 

 be determined quantitatively in urine? What is hippuric acid, and by what 

 tests may it be recognized ? What points are to be considered, and what sub- 

 stances determined, in the analysis of normal and abnormal urine? What is 

 the color of urine, and what are the chief causes influencing the color ? What 

 is the specific gravity of healthy urine, how is it determined, and how is the 

 total amount of solids approximately calculated from the specific gravity? 

 Describe the different tests by which albumin may be recognized, and state the 

 precautions necessary in making these tests. How may the quantity of al- 

 bumin in urine be determined approximately, and also accurately? Describe 

 the various tests for sugar. On what principles are they based, and how can 

 sugar be distinguished from other reducing substances occurring in urine? 

 How is sugar determined quantitatively ? By what tests are biliary pigments 

 and acids recognized in urine? What is the nature of urinary sediments, and 

 by what means are they recognized? What are urinary calculi generally com- 

 posed of, and by what simple tests can their nature be determined? 



