304 Dr. Schaf haeutl on the Different Species of Cast IroUi S^c, 



— 7*08 grains. The same quantity of the same iron treated 

 in the above-mentioned manner with nitric acid of I'lO spe- 

 cific gravity left residuum 3 •24 grains ; no trace of sulphuric 

 acid could be discovered in the liquid. By boiling the re- 

 mainder in a platinum crucible with strong nitric acid, the 

 greatest part of the sulphur was separated, which adhered 

 slightly as a yellow riband to the side of the crucible, and no 

 traces of sulphuric acid were to be found in the solution. The 

 sulphur thus separated from 1'55 grains of the residuum 

 weighed 01 80 grains, and this burnt on a platinum foil left 

 0"100 sulphuret of iron. That which the nitric acid had 

 dissolved during the boiling was precipitated with caustic 

 ammonia and consisted of 



Iron 0'443 



Phosphorus . . . 1 55 

 And left residuum . 0*31 

 Humine .... 0*33 



We see therefore that the sulphur had been in combina- 

 tion with the iron, approaching in this formula F^ S, that is in 

 a certain well-known state of chemical proportions. 



Another remarkable circumstance is the difference of the 

 products of solution according to the difference of the specific 

 gravity of the acid, which throws a light on several chemical 

 products, which arise from different degrees of concentration 

 of chemical agents, and the varying products obtained by the 

 various degrees of heat. 



In hydrochloric acid we have a juxtaposition of atoms of 

 chlorine and hydrogen intermixed with atoms of hydrogen 

 and oxygen ; and the interposition of a certain quantity of 

 atoms of water betwixt a certain number of atoms of chlorine 

 and hydrogen, alone determines how many atoms of the iron 

 shall combine with chlorine to form protochloride of iron, and 

 how many atoms of hydrogen shall form compounds with car- 

 bon and azote. 



The description of the residuums left by treating iron with 

 acid was always a matter of great speculation. Berzelius 

 says the remainder of the solution of iron in sulphuric acid 

 was black, in hydrochloric acid gray, and sometimes white. 



The colour of the residuum, as shown, depends partly on 

 the specific gravity of the iron and partly on its chemical 

 composition. 



The residuum of white cast iron prepared with coke as 

 fuel, in hydrochloric acid is always brown, yellowish brown 

 or greenish brown ; the remainder of very gray coJce iron is 

 always light gray, in different shades approaching to white. 

 [To be continued.] 



