ANALYSIS OF IRON ORES, &C. 4| , 



maiiiing so ignorant of the causes of the bad quality of 

 iron. 



Mr. Vauquelin however admits, that there is likewise a Phosphorus. 

 small quantity of phosphorus converted into acid, and dis- 

 solved in the liquor, probably in the state of phosphate of 

 iron, by means of the sulphuric acid. It appears to hinj, 

 that, when the sulphuric acid is less diluted with water, a 

 larger quantity of phosphorus dissolves in the liquor. To 

 separate this })hosphate of iron, he dilutes the solution with Separation of 

 seven or eight parts of water, and mixes with it carbonate ^^®. Phosphate 

 of potash, till almost the whole of the acid is saturated, A 

 white precipitate is formed, more or less copious according 

 to the kind of iron employed ; and at the expiration of a 

 few days it grows yellowish. This precipitate, washed and 

 dried, he treats with potash in a silver crucible at a red 

 heat: he then lixiviates the matter with water, and, after 

 having saturated the liquor with nitric acid, and boiled it to 

 expel the carbonic acid, he adds limewater, which commonly 

 forms a white flocculent precipitate, or semitransparent if 

 phosphoric acid be present. 



He has likewise found a large quantity of chrome in tlie Chrome oxi- 

 precipitate produced by carbonate of potash in the solution ge^ized and 

 of pig iron by sulphuric acid. It follows therefore, that su\^^°h uric Tcid. 

 chrome as well as phosphorus is oxigenized and dissolved in 

 sulphuric acid. 



It is advisable to test the alkaline liquor with nitrate of Caution. 

 ammonia, previous to saturating it, in order to know whe- 

 ther it hold any silex or alumine in solution. If it do, a 

 sufficient quantity should be added to precipitate these 

 earths, after which they must be separated by the filter: 

 for without this precaution they would be precipitated by 

 the lime, and might be mistaken for phosphate of lime. 

 Mr. Vauquelin has found very evident traces of this salt in 

 the pig iron of the works atDrarnbon, though he employed 

 sulphuric acid diluted with six parts of water to dissolve it: 

 there was much less however, than remained in the residuum 

 of the solution. This was the only kind of pig iron he ex- 

 amined, but he conceives it probable, that all the irons 

 from bog ores contain the same foreign matters. 



VI. 



