OF ARKANSAS. J go 



III. The mineral is treated with strong hydrochloric acid, solution evapo- 

 rated to dryness, residue treated with dilute hydrochloric acid, and silica 

 collected on filter. 



IV. Filtrate diluted with water, and baryta precipitated with sulphuric 

 acid. 



V. Filtrate nearly neutralized with carbonate of soda, and iron and 

 alumina precipitated with carbonate of baryta; separated as described 

 above, in the analysis of smithsonite. 



VI. After removal of baryta with sulphuric acid, the filtrate is neutral- 

 ized with ammonia and precipitated with sulphhydrate of ammonia in a 

 well-closed bottle; the precipitate is allowed to settle, collected on a filter, 

 washed with water containing sulphhydrate of ammonia, and digested with 

 dilute hydrochloric acid [the small quantity of sulphurct of cobalt which 

 remains undissolved is collected on a filter and strongly ignited]; from the 

 solution the manganese is precipitated with carbonate of soda, and the 

 precipitate ignited until the weight remains constant. 



VII. In the filtrate from the sulphurets, the lime is determined as usual. 



LIMONITE, 



Containing : Insoluble silicates; water; sesquioxides of iron and manga- 

 nese, alumina; phosphoric acid; lime, and magnesia. 



I. Water determined by ignition. 



II. The pulverized mineral is boiled with strong hydrochloric acid until 

 the residue appears colorless; the whole evaporated to dryness; the dry mass 

 treated with dilute hydrochloric acid, and insoluble silicates collected on 

 filter. 



III. The filtrate is diluted to 250 cub. cent.; of these 



50 cub. cent, are used for the determination of iron by means of chamadeon 

 mineral. 



50 or 100 cub. cent, are used for the determination of phosphoric acid by 

 means of molybdate of ammonia. 



100 cub. cent, are nearly neutralized with carbonate of soda, acetate of 

 soda added and heated to ebullition until the liquid appears colorless; the 

 precipitate is collected on a filter, washed, dissolved in hydrochloric acid, 

 and reprecipated with ammonia; it contains all the iron, alumina, and 

 phosphoric acid; the filtrate is treated as in IV. 



IV. To the filtrate some hypochlorite of soda is added, and enough 

 acetic acid to produce acid reaction, and allowed to rest for 24 hours; the 

 peroxide of manganese is collected on a filter, and ignited [if the precipi- 



