APPARATUS. 329 



Analysis for Chlorides Approximately. Fill a 

 Marais graduated tube to the ounce mark with, fil- 

 tered urine, make strongly acid with nitric acid; pro- 

 vide a solution ot nitrate of silver, forty grains to the 

 ounce of water; add an excess of this to the urine in 

 the tube, allowing the whole to remain quiet for twenty- 

 four hours. At the expiration of this interval the 

 volume of precipitate may be read from the graduated 

 scale, each .2c.c. of precipitate will equal 0.19 grains 

 of chloride of sodium ; in the above approximate anal- 

 ysis the acid must not be omitted, otherwise a precipi- 

 tate of phosphate of silver might vitiate the results. 



Analysis for Phosphoric acid. Dry carefully a suffi- 

 cient quantity of chemically pure nitrate of uranium, 

 using gentle heat; of this take 106 \ grains and add 

 3,000 grains of distilled water; 200 grains of this 

 standard solution equals one grain of phosphoric acid. 



Solution of Acetate of Soda. Four hundred grains 

 of acetate of soda are dissolved in six fluid ounces of 

 water, and to the solution add 800 grains of acetic 

 acid. The commercial article known as "No. 8" will 

 answer. 



Solution of Ferro-cyanide of Potassium is made by 

 dissolving one part of the salt in ten parts of water. 



Test Solution. Dissolve 50.4 grains of phosphate of 

 soda in 1,000 grains of water; 100 grains of this solu- 

 tion equals one grain of phosphoric acid. 



To Test the Standard Solution. Measure fifty grains 

 of the above test solution into a beaker; add one-fourth 

 volume of the acetate of soda solution, increase the 



