142 NEW TOEK STATE MUSEUM 



silicon tetra fluoride. 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 hydrochloric acid, and reprecipitated in the same way ; fil- 

 tered out, washed and then ignited and weighed, giving the amount 

 of alumina and iron (as Fe^Og) present. The combined filtrates 

 from the iron and alumina, which should be concentrated to 

 about 200cc., 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 sulphuric acid, and weighed as 

 calcium sulphate. The filtrate receives a further addition of 

 ammonia and of hydrodisodic phosphate, is well stirred, allowed to 

 stand for some hours in the cold, when the magnesium precipi- 

 tate is filtered out, washed with ammonia, ignited and weighed. 



In case manganese is present, the filtrate from the silica is 

 neutralized as closely as possible, sodium acetate solution added, 

 the solution diluted largely, and boiled for about a minute and 

 filtered as rapidly as possible, the precipitate washed with boil- 

 ing water, redissolved in dilute hydrochloric acid and reprecipi- 

 tated in the same way, washed, ignited and weighed as Fe 2O3 

 and A.I3 O3. The combiaed filtrates from the iron and alumina 

 are evaporated to about SOOcc, bromine water added and the 

 solution boiled when the manganese is precipitated as Mn Og. 

 This is filtered out, dissolved in a little dilute hydrochloric acid, 

 a solution of microcosmic salt added, the solution heated to boil- 

 ing and the a ammonia add. d to exact neutrality, any excess of 

 ammonia being removed by heating on the water bath. The 

 precipitate of manganese ammonium phosphate is filtered out, 

 ignited and weighed as MngPaO-. The filtrate from the 

 manganese precipitation is acidified with hydrochloric acid, boiled 



