240 § 122. FEETILIZERS. 



in very dilute hydrochloric acid, determine sulphuric acid 

 in tlie solution by precipitation with baric chloride (§ 59), 

 deduct so much of the sulpbuiic acid as is estimated to 

 have been combined with the lime and magnesia, and de- 

 duct also the corresponding quantity of sulphates from 

 the total amount of sulpliatcs, and with these remainders 

 estimate the potassa and soda by the formula for the in- 

 direct determination of these bases (§ 46, e). 



e. Nitric acid. — This may be determined by Schloss- 

 ing's process in 10-20 c.c. of the aqueous solution ob- 

 tained in b, or by fusion of about 2 grms. of the salt with 

 silicic acid (§ 62). This estimation can be dispensed 

 with, since the weight of the nitrates equals the difterence 

 between the. total amount of salt taken, and the sum of 

 the sulphates and chlorides, as already determined. 



f. If the Chili saltpetre is adulterated with salt, its so- 

 lution will give an abundant precipitate with argentic 

 nitrate ; if adulterated with soda (sodic carbonate) it will 

 rrive the reaction for carbonic acid ; if with magnesic sul- 

 phate (Epsom salts), it will give a decided reaction for 

 sulphuric acid and for magnesia ; and if with sodic sul- 

 phate (Glauber's salt), it will give a decided reaction for 

 sulphuric acid, but none for magnesia. 



