1824.] Discovery to Copper Vessels used for Culinary Purposes. 177 



of muriate of barytes, it appeared to be free from sulphuric acid. 

 Sheets of copper were used two inches in length by one in 

 breadth, having, therefore, a surface of four square inches. 



2. Three pieces of copper, weighing respectively 78, 77, and 

 v 74*5 grains, were each immersed in f % jss of acetic acid, the 



first without any addition, the second with a sheet of tin of the 

 same size with itself, and weighing nine grains, placed at about 

 an inch from it in the fluid ; the third, with a similar plate of 

 tin closely applied to one of its surfaces. 



3. In 37 days the acid in No. 1 had acquired a fine blue 

 tinge, was char and transparent; the copper was tarnished, 

 exhibiting a blackish mottled appearance ; it was found to have 

 lost 1*6 grain. 



4. The copper that was placed opposite to the tin was consider- 

 ably tarnished and blackened, and was found to have lost 2-2 grs. 

 The tin was evidently much eroded, and on the side opposite to 

 the copper was covered with a black coating which was not 

 easily detached from it ; the fluid was opaque, and of a light- 

 yellow colour, and contained a considerable quantity of a 

 light-yellow precipitate. The tin was digested in ammonia ; the 

 ammonia gradually acquired a fine blue colour, and the tin was 

 left perfectly clean, but with its surface exhibiting the appear- 

 ance which has been termed moirte ; it had lost 2*5 grains. The 

 acid, after some days, deposited the yellowish substance, and 

 became transparent; in this state it was not precipitated by 

 potash. 



5. The copper that was in contact with the tin was very 

 slightly tarnished on the part exposed to the acid, and exhibited 

 undulating lines of prismatic colours which were extended 

 between the edges of the tin ; its weight was not affected. The 

 tin was evidently eroded ; the surface in contact with the cop- 

 per exhibited lines of prismatic colours, running in various 

 directions ; while the outer surface exhibited the moireje appear- 

 ance ; it had lost *9 grain. The fluid exhibited the same pro- 

 perties with that in No. 4, but in a less degree. 



(J. For the purpose of comparison, a similar piece of tin was 

 immersed without addition in acetic acid; it was eroded, exhi- 

 bited on both sides the moirte appearance, and was found to 

 have lout 1 -rain ; the fluid resembled that in No. 5. lit nee it 

 would appear that when copper is immersed in acetic acid 

 with half its surface covered with tin, and the other half exposed, 

 the copper is not dissolved by the acid. When the copper and 

 tin ;ne both immersed in the acid, but not in contact, the copper 

 is dissolved in considerably greater quantity than when the tin 

 is not present, but the whole of the dissolved copper is precipi- 

 tated upon the surface of the tin. With respect to the action of 

 acetic acid upon tin, when the same quantities of the materials 

 are employed, the tin being either simply immersed in the acid, 



New Sail's, vol. vni. n 



