J68 AGRICULTUnAL MUSEUlVl 



To separate these from each ot!i-i-, t!ic ^Olid matter 

 should be boiled for two or three hours with sii'phnrie 

 a:i\ i dl.uted *vith four times its weight of water; the 

 q'unlity of the acid sliould bo rcj^ulatcd by the quan- 

 tity of solid le-^iduum to be acted on. allowing for eve- 

 ry hun»hvd grains two drachms or one h ndred and 

 t>vent} grains of acid. 



Tie subs.ancc remaining after the action of the 

 acid, may be c xisidored as silieions ; and it must be 

 separated and its wei.'^r'it ascertained, after washing 

 and dry tig in the usual manner. 



The a' imine and the oxide of iron, if any exist, are 

 both dissolved by the sulphuric acid ; they may be se- 

 parated by carb;)niite oi ammoniac, added to excess ; 

 it throws down the alumine. and leaves the oxide of iron 

 in solution, and this substance may be separated from 

 the liquid by boiling. 



Should any magnesia and lime have escaped solution 

 in the mu. iatic acid, they will be found in the sulphuric 

 acid ; this, however, is scarcely ever the case ; but the 

 process for detecting thtm and ascertaining their quan- 

 tities, is the same in both instances. 



The method of analysis by sulphuric acid, is suffici- 

 ently precise for all usual experiments ; but if very great 

 accuracy be an object, dry carbonate of potash must be 

 employed as the agent, and lliecesidnum of the incinera- 

 tion must be heated red for a half hour, with four times 

 its weight of tfiis substance, in a crucible of silver, ot of 

 "tvell bakfd porcelain. The mass obtained must be dis- 

 solved m the mui iaiie acid, and the solution e^ apora- 

 led till it is neai-!y solid ; distilled water must then be 

 added, by which the oxide of iron and all the earths, 

 except silex, w'll be dissolved in combination as muri- 

 ates. The silex, aftc- the usual process of lixiviation, 

 must be heated red ; tiie other substances may be sepa- 

 rated in the sume manner as from the muriatic aud eub 

 |)huric solutions. 



