218 Miscellaiiebuh Intelligence, 



dissolves the oxide formed : bein^ again withdrawn, the oxidation 

 recommences, and proceeds as before ; and operating thus, in a very 

 few days the acid is entirely saturated. 



This process was proposed by M. Berard, sen., many years ago, for 

 the solution of tin in muriatic acid ; and at present three important 

 applications of it are made in the manufactory at Montpellier, in 

 the preparation of blue vitriol, muriate of tin, and acetate of lead. 



In the preparation of blue vitriol, 4 or 5 leaden vessels are filled 

 with pieces of laminated copper, as old copper, sheathing, &c. The 

 metal in all the cases is moistened with weak sulphuric acid (sp. gr. 

 1.114 to 1.155), and left exposed to air for some time; then the 

 first vessel is filled with similar acid, which, after a few hours, is 

 transferred to the second vessel, then to the third, and so on in suc- 

 cession, until the hydrometer shews that it is saturated, or nearly so, 

 with oxide. By this method a solution may be obtained, which 

 does not require to be evaporated to less than one half before it will 

 yield fine crystals ; they are scarcely acid, and are consequently free 

 from iron. 



In the preparation of muriate of tin, the granulated tin is put 

 into vessels of glass or earthenware, and muriatic acid poured upon 

 it ; action immediately commences, and hydrogen is evolved : if, 

 after a short time, the acid is withdrawn and the vessels left open, 

 at the same time that the moistening acid acts, evolving hydrogen, 

 so great a portion of the oxygen of the air combines with the metal 

 that the whole heats powerfully. On restoring the acid to the 

 metal, it dissolves more oxide than it would have done without the 

 use of the air, even though heat had been applied. By trans- 

 ferring the acid to be saturated from one vessel to another, a solu- 

 tion of proto-muriate of tin is quickly obtained, which merely 

 requires a little evaporation to yield the salt in very fine white 

 needles. 



Acetate of lead is usually made by dissolving litharge in acetic 

 acid, more or less diluted. In M. Berard's manufactory, the lead 

 is granulated in as thin portions as possible, and a wooden vessel, 

 as the half of a cask, filled with it ; it is then moistened with weak 

 acetic acid (distilled vinegar), and the tub covered with a board. 

 In a few minutes, so much heat is evolved, that acetic acid is vola- 

 tilized: more acid, then poured upon the lead, dissolves a large 

 quantity of oxide; and by two or three such operations, not only a 

 solution of the acetate, but of the subacetate may be obtained. The 

 operation is so quick that three or four tubes suffice to supply a 

 large quantity of the acetate. The solution is then evaporated in 

 copper vessels, with the usual precautions : the mother liquor is 

 evaporated with fresh solutions, and when, by these repeated ope- 

 rations, it becomes too coloured, it may be cleansed by the use of 

 animal charcoal, like sugar. 



M. Berard has no doubt that a similar process might be eco- 

 nomically adopted in the manufacture of verdigris in the central 



