CLAYS OF NEW YOEK 531 



more or less refractory character of the claj. The fusion is trans- 

 ferred to a porcelain casserole, dissolved in water, and the solution 

 acidified with hydrochloric acid; the solution is then evaporated to 

 dryness, and the casserole mth its contents placed in a drying oven 

 at 105° to 110° C, and allowed to remain till all the hydrochloric 

 acid is expelled. The silica present is thus rendered insoluble. 

 Hydrochloric acid and water are now added; the casserole is warmed 

 for a few minutes on the water bath and the solution filtered, the 

 silica being washed with hot water till the washings are free from 

 chlorin. The silica is then ignited and weighed, and, as it is likely 

 to retain small quantities of alumina, it is treated mth hydrofluoric 

 and sulfuric acids and heated, the silica being thus volatilized as 

 silicon tetra-fluorid. The residue from this treatment is weighed, 

 and its weight added to that of the alumina subsequently found. 



If the original fusion of the clay showed little or no green color, 

 the filtrate from the silica is treated with a slight excess of ammonia, 

 and the solution boiled for a short time to expel the excess. The 

 solution is then filtered, the precipitate dissolved in dilute hydro- 

 chloric acid, and reprecipitated in the same way; filtered out, 

 washed and then ignited and weighed, giving the amount of 

 alumina and iron (as Te^ O g) present. The combined filtrates from 

 the iron and alumina, wh^ch should be concentrated to about 200 cc, 

 are heated to boiling and about 25cc of sat sol. of ammonium 

 oxalate added, and the boiling continued for two or three minutes 

 longer, when the heat is removed and sufiicient ammonia added to 

 render the solution strongly alkaline. The precipitate is allowed to 

 settle, and the supernatant liquid decanted off as closely as possible 

 through a filter; hydrochloric acid is then added to the precipitate 

 to dissolve it, and then sufficient ammonia to reprecipitate it. It is 

 then washed on to the filter; washed; ignited with sulfuric acid, 

 and weighed as calcium sulfate. The filtrate receives a farther 

 addition of ammonia and of hydrodisodic phosphate, is well stiiTed, 

 allowed to stand for some hours in the cold, when the magnesium 

 precipitate is filtered out, washed with ammonia, ignited and 

 weighed. 



