On Metallic Salts. 247 



4:rorrect, and that he had never tried that which he gives as a 

 fact, will appear by experiment. The greater proportion of free 

 acid, so far from rendering a metallic salt more soluble, will in 

 most instances precii>itate it; — this also appears to prove the 

 watery solution to be a super-salt ; for were it held in solution 

 merely by free acid, acid in any proportion could not precipi- 

 tate it, — otherwise each acid would become-L»oth the solvent and 

 precipitant of its corresponding salts. To me the solution ap- 

 pears to depend entirely on the water. The nitrates of lead and 

 silver are precipitated by nitric acid, the nitrates of iron, zinc, 

 and copper by sulpiiuric acid, in the state of sulphate ; whereas 

 if nitric acid is dropped into a solution of a sulphuric salt, no 

 precipitate is formed, as the water required to dissolve it is 

 sufficient even after the addition of nitric acid to hold it in so- 

 lution ; but the nitrates of these metals being more soluble than 

 the sulphates, do not afford, when sulphuric acid is added, suf- 

 ficient water to keep the sulphate in solution; and these preci- 

 pitates may be alternately taken up by water and precipitated 

 by acid — nevertheless G. S. insists the acid is the solvent. 



" Metallic salts aregenerally, if not universally, more soluble," 

 says your correspondent, " according to the greater proportion 

 of free acid." By this it will plainly appear that his experiments 

 must have been extremely confined, or that the inaccuracy of 

 them hurried him into error ; as it is the deliquescent metallic 

 salts which will not jirecipitate on the addition of acid ; as on the 

 contrary, permanent salts arc precipitated by it. Therefore G. S. 

 either made his experiments on deliquescent salts alone, or used 

 dilute acid, or dilute sohitions. He cannot then with propriety 

 assert the solution depends on free acid, where water is present, 

 and that in a greater proportion than in acids of the usual spe- 

 cific gravity. 



Your correspondent says, Me cannot conceive anv period du- 

 ring the formation of a salt, that the action towards chemical 

 union would cease, whilst a ])ortion of both its constituents re- 

 main in contact and uncombined. This I believe is the general 

 opinion : let me then draw your attention to the process of 

 forming sulphate of iron. See. We find in this, that after the ac- 

 tion ceases, the solution by test is acid, although a quantity of 

 the iron (if sufficient were introduced) still remains undissolved: 

 therefore, as he asserts, the acid in the solution is free, that is 

 uncombined — the uncombined acid is consequently by his rule 

 in contact with the iron, &c. without acting on it; and this he 

 protests cannot be the cjise, — Now, were it allowed tly^t the ex- 

 cess of acid, instead of being free, was combined with the metal 

 to form a salt, then it would be natural to conclude the metal 



Q 4 would 



