CALCIUM SALTS. TYROSEN. 211 



423. Make normal urine alkaline with sodium hy- 

 drate and examine the precipitated calcium and magne- 

 sium phosphates with the microscope. Try their solubility. 



CALCIUM SULPHATE. 



This does not often occur as a sediment. It may be 

 found in acid urines as long prisms united in clusters. 

 (Plate II, 12, a.) 



424. Prepare crystals of calcium sulphate by pre- 

 cipitating a rather dilute solution of calcium chlorid with 

 a few drops of sulphuric acid. Dissolve the precipitate in 

 boiling water, filtering hot if all does not dissolve. It will 

 reprecipitate upon cooling. Examine with the microscope. 



CALCIUM CARBONATE. 



This compound is often found in alkaline urine with 

 calcium phosphate. It appears as a sandy powder which, 

 when examined microscopically, is seen to consist of 

 spherical bodies formed of concentric layers or to have 

 the dumb-bell shape of calcium oxalate. (Plate II, 9.) 

 It dissolves readily in acetic or other acids, with the evolu- 

 tion of carbon dioxid gas. 



TYROSIN. 



Tyrosin is not often found as a sediment because of 

 its solubility in water, but it sometimes appears as such, 

 though never in a normal condition of the system. It 

 crystallizes in minute needle-shaped crystals, which are 

 usually aggregated into clusters or sheaves. (Plate II, 

 12, c.) Its microscopic appearance is the best means of 

 identifying it. The chemical tests have been given. 



