An Attempt to analyse Cast Iron. 351 



When dissolved again in muriatic acid, and precipitated 

 with prnssiate of potash, it produced a white precipitate, 

 which by degrees assumed a purple tint in the air, and by 

 the blow-pipe proved to be manganese. Caustic potash 

 separated from the remaining sohition a veslige of magnesia. 



7. The alkaline solution remaining after the precipita- 

 tion of the oxide of manganese produced no alumina when 

 super-saturated with muriatic acid, and thereafter mixed 

 with carbonate of ammonia. This cast iron, therefore, had 

 not contained anv sensible quantity of alumina. 



8. The liquor of the solution which had been precipi- 

 tated with caustic ammonia (see No. 4.) was now eva- 

 porated to two-thirds in a well covered porcelain vessel, 

 after which it was mixed with oxalic acid : in 24 hours it 

 deposited a most inconsiderable quantity of a white 

 powder, which changed to red in drying, but after burning 

 blackened, and had the properties of manganese. The 

 remaining fluid mixed with sub- carbonate of potash, and 

 boiled till all ammonia was expelled, did not deposit any 

 thing, and had therefore not retained any magnesia. 



But before I proceed to sum up the results from this 

 analysis, I must give an account of some remarkable cir- 

 cumstances attending the separation of the substances met 

 with in the cast iron. The first relates to the iron and the 

 manganese. VVe know the certainty derived from the old 

 method of using the neutral succinates, but this acid is 

 unfortunately too expensive to be applied where the greater 

 portion is oxide of iron. The action of benzoic acid up- 

 on the oxides of iron and manganese perfectlv resembles 

 that of the succinic acid ; and Mr. Hisinger has already 

 proved that it also may be considered as possessing certain 

 advantages over the latter. But one circumstance deserves 

 notice, which might lead to an incorrect result; namely, 

 that the benzoic acid during the evaporation of its salts is 

 partially volatilized, and leaves a basic salt in the dried 

 mass. The benzoat of ammonia is however an exception 

 from this, for it always becomes acid. These basic salts 

 precipitate so much of n)angane?e as the surplus of their 

 base can afford, and thus produce a diminished result. But 

 it the solution is acid, no manganese will precipitate, and 

 iron alone is di.'positcd, along wiili the difKcuitly soluble 

 acid. It is plain that tlie free acid of the mixture must Ije 

 no other than benzoic acid, in order that decomposition 

 and precipitation may take place. The latter refers to the 

 oxide of manganese and to the magnesia, for the separa- 

 Hoii of whicii 1 do not yet know any infallible method. 



Vauqueiin's 



