256 DR. CHARLES A. BURGHARDT ON THE 



oxide. In a former communication to this Society (Proc. 

 Lit. and Phil. Soc. xvii. 1877-78^ pp. 27-36) I mentioned 

 that on heating some crystals of cuprous chloride in water 

 in a sealed tube^ at a temperature ranging from i6o°- 

 180° C, minute green spots of a substance resembling 

 atacamite were observed upon the sides of the tube. 

 Further^ on heating cuprous oxide and a strong solution 

 of chloride of sodium together in a sealed tube_, at 1 50°- 

 180°^ chalcotrichite was formed, and also a green substance 

 resembling atacamite. 



Wishing to ascertain whether atacamite could be pre- 

 pared in larger quantity (in accordance with my supposi- 

 tion that all the copper-ores are products of the decom- 

 position of cuprous oxide, the latter substance being a 

 secondary product of the oxidation of the metal itself), I 

 made numerous experiments, mostly consisting in the 

 heating of cuprous oxide with sodium-chloride solution in 

 sealed tubes, and obtained excellent results by simply 

 covering a quantity of cuprous oxide with a concentrated 

 solution of sodium chloride, exposing this mixture to the 

 air at the ordinary temperature, and stirring it up occa- 

 sionally. By proceeding in this way, a very concentrated 

 solution of cuprous chloride in sodium chloride can be 

 obtained. After standing a few days, this solution begins 

 to decompose, a green insoluble substance separating out 

 continually, which can be easily filtered off" from the liquid 

 portion and well washed in cold distilled water in order to 

 free it from all traces of cuprous chloride and sodium 

 chloride. The substance thus obtained was carefully dried 

 over calcium chloride until its weight was constant, and 

 portions weighed out and analyzed quantitatively, with the 

 following result, viz. : — 



