OF ARKANSAS. 189 
Ill. 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 sulphuret of cobalt which 
remains undissolved is collected ona 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. 
é 
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. 
Ill. The filtrate is diluted to 250 cub. cent.; of these 
50 cub. cent. are used for the determination of iron by means of chameleon 
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- 
