124 Prof. Field on some of the Basic Salts of Copper, 



No difficulty was experienced in obtaining the artificial salt of 

 definite composition, by the addition of a small quantity of 

 caustic potash to a great excess of sulphate of copper, and boiling 

 for some time. On filtering off the excess of sulphate, and 

 washing for many clays until no trace of sulphuric acid or cop- 

 per could be detected in the filtrate, the bright-green powder, 

 after drying at 212° until it ceased to lose weight, gave on 

 analysis, 



Oxide of copper . . . 67*51 

 Sulphuric acid .... 16*98 

 Water (by difference) . 15*51 



100*00 



agreeing very closely with the formula 3CuO, CuO SO 3 , 4 HO, 

 which involves the following numbers : — 



4 Oxide of copper . . . 67*63 

 1 Sulphuric acid . . . 17*04 

 4 Water 15*33 



100*00* 



The copper was estimated by two methods : (1) by dissolving 

 the salt in dilute nitric acid, and precipitating the oxide by a 

 slight excess of potash ; and (2) by heating it to whiteness in a 

 platinum crucible. The residue consisted entirely of oxide of 

 copper, and on examination showed no trace of sulphuric acid. 



When a solution of hypochlorite of lime is employed in place 

 of the caustic alkali (the sulphate of copper being in excess), no 

 basic sulphate is formed, the green precipitate consisting entirely 

 of the oxychloride, the formula of which is in most instances 

 3 CuO, CuCl, 4HO, but upon one or two occasions (dependent 

 apparently upon the length of the time of ebullition) of 

 3 CuO, CuCl, 6 HO. This is somewhat remarkable, inasmuch 

 as the native oxychloride (atacamite), which generally contains 

 4 atoms, sometimes is found with 5 ; and Berthier many years 

 ago analysed a specimen from Cobija (Bolivia) containing 6 

 equivalents. The artificial compound obtained by myself, and 

 the natural one examined by Berthier, agree very closely. 



Native. Artificial. Calculated. 



3 CuO. . . 50*00 49*85 49*56 



lCuCl. . . 28*25 28*02 28*01 



6HO . . . 2175 22*13 22*43 



100*00 100*00 100*00 



When hypochlorite of soda instead of hypochlorite of lime is 

 employed, the same compound (oxychloride of copper) is preci- 



* Cu = 31*7. 



