218 



ANALYSIS OF CALCULI. 



Precipitate is cal- 

 cium oxalate. Test 

 after washing and 

 drying by heating 

 to a bright-red heat 

 on platinum foil. 

 After cooling it 

 should turn moist 

 red litmus - paper 

 blue. 



To the filtrate add ammonium oxalate, 

 boil, and, if there is a precipitate, filter Avhile 

 hot. 



A white precipi- 

 tate shows cal- 

 cium, probably 

 originally present 

 as phosphate or 

 carbonate. 



The filtrate is to be 

 tested for magnesium 

 and plwsphoric acid. For 

 Mg make one-half alka- 

 line with ammonia and 

 if the liquid remains 

 clear, add sodium phos- 

 phate. A fine, white 

 crystalline precipitate 

 with either reagent in- 

 dicates Mg. For phos- 

 phoric acid make re- 

 mainder acid with strong 

 HNO 3 and add ammo- 

 nium molybdate. A yel- 

 low precipitate appears. 



Urates of K, Na, and Ca can be found by boiling the 

 powdered calculus in water, filtering, and testing the fil- 

 trate by the murexid test. Or if it is evaporated to dryness 

 and the residue is ignited on platinum the sodium and 

 potassium will remain as carbonates, giving an alkaline re- 

 action to litmus-paper. 



THE METEIC SYSTEM. 



In all work in modern chemistry the metric system 

 of weights and measures is employed. The unit of length 

 is the meter (39.37 inches); of weight is the gramme (or 

 gram), which is the weight of 1 cubic centimeter of water 

 at 4; and, of capacity, the liter, which has the volume of 

 1 cubic decimeter. 



