C 150 ] 



separated and its weight ascertained, after washing 

 and drying in the usual manner. 



The alumina and the oxide of iron and mangane- 

 sum if any exist, are all dissolved by the sulphuric acid ; 

 they may be separated by succinate of ammonia, ad- 

 ded to excess : which throws down the oxide of iron, 

 and by soap lye, which will dissolve the alumina, but 

 not the oxide of manganesum ; the weights of the 

 oxides ascertained after they have been heated to red- 

 ness will denote their quantities. 



Should any magnesia and lime have escaped so- 

 lution in the muriatic acid, they will be found in the 

 sulphuric aqid ; this, however, is rarely the case ; but 

 the process for detecting them, and ascertaining their 

 quantities, is the same in both instances. 



The method of analysis by sulphuric acid, is suf- 

 ficiently precise for all usual experiments ; but if very 

 great accuracy be an object, dry carbonate of potassa 

 must be employed as the agent, and the residuum of 

 the incineration (6) must be heated red for a half hour, 

 with four times its weight of this substance, in a cruci- 

 ble of silver, or of well baked porcelain. The mass 

 obtained must be dissolved in muriatic acid, and the 

 solution evaporated till it is nearly solid ; distilled 

 water must then be added, by which the oxide of iron 

 and all the earths, except silica, will be dissolved in 

 combination as muriates. The silica, after the usual 

 process of lixiviation, must be heated red j the other 

 substances may be separated in the same manner as 

 from the muriatic and sulphuric solutions. 



