176 SPECIMENS OF IRON ORE, 



except the silica, alumina,* pbosphuret of iron (if any exists), sulphate and 

 phosphate of lime: filter and wash the residuum perfectly, and calcine it : 

 its weight is that of the silica and alumina — it may be tested for phos- 

 phate and sulphate of lime, if necessary. 



3. — To separate the alumina, boil on the residuum sulphuric acid, di- 

 luted with thrice its weight of water, this will dissolve the whole of it, 

 and leave the silex untouched. 



4. — Evaporate the muriatic solution at a gentle heat ; when nearly 

 dry, pour upon it about half a pint of well boiled distilled water, transfer 

 the whole to a jar or flask, and keep it closely stopped for twenty-four 

 hours : if any precipitate forms, it is phosphate of iron, which may be 

 separated as usual. 



5. — Drop sulphuric acid into the solution, the lime, if any, will pre- 

 cipitate as a sulphate ; separate it and calcine at a low red heat, and by 

 the scale of equivalents, the quantity of carbonate of lime may be known. 



6.. — Precipitate the solution by one of caustic soda; filter, wash, 

 calcine, and weigh the residuum, which consists of the mingled oxides of 

 iron and manganese. 



7 — ^Digest these in nitric acid, with a gentle heat, allow it to re- 

 main exposed to the air till nearly dry, calcine again at a red heat, stir- 

 ring it often, and weigh it ; if any increase of weight has taken place, 

 oxygen has been absorbed, and this must be allowed for in the results. 



^ 8.— To 



* None could be detected in repeated trials. 



