SIDERITE. 47 



dried, and gradually heated to redness in a porcelain 

 crucible, with free access of air ; till it is converted into 

 pure sesquioxide of iron. 



The filtrate is feebly acidulated with hydrochloric 

 acid, evaporated to dryness, and heated till all ammo- 

 niacal salts are expelled. 



The residue is then dissolved in a small quantity of 

 water, with addition of hydrochloric acid, the solution 

 saturated with chlorine, and the manganese precipitated 

 as hydrated sesquioxide by addition of ammonia. The 

 liquid is rapidly filtered off, so that no carbonate of 

 lime may be precipitated, and the manganese-precipi- 

 tate washed, dried, and ignited, when it is converted 

 into brown proto- sesquioxide. 



The lime and magnesia in the filtrate are separated 

 as in No. 12. 



Or the manganese may be precipitated by sulphide 

 of ammonium, the sulphide of manganese rapidly fil- 

 tered off, and dissolved in hydrochloric acid. When 

 all the sulphuretted hydrogen has been expelled by 

 evaporation, the solution is heated with carbonate of 

 soda, when the manganese is precipitated as carbonate, 

 which, after ignition, leaves the brown proto-sesqui- 

 oxide. 



From the solution filtered from the sulphide of man- 

 ganese, the lime and magnesia are precipitated as in 

 No. 12. 



II. The acid solution is largely diluted with water, 

 and carbonate of soda gradually added (drop by drop, 

 when the solution is neutral), with constant stirring, 

 until all the sesquioxide of iron is precipitated. The 

 other bases remain dissolved in the free carbonic acid. 

 The manganese is then best precipitated by hypochlo- 

 rite of soda, in the cold. 



III. When a larger quantity of manganese is present, 

 the solution, which must contain the iron entirely in 

 the form of sesquichloride, and must not be too acid, 



