Prof. Field on some of the Basic Salts of Copper. 123 



by his profound investigations, has made the dynamical theory 

 of heat, as applied to cosmical phenomena, his own. 



I sincerely trust that, by the foregoing remarks, I have done 

 no injustice to Mayer, especially as I grieve to hear that sickness 

 has removed him (I hope for only a short time) from the science 

 to which he has contributed w T ith so much ability. The repro- 

 duction of some of his papers in the Philosophical Magazine, 

 particularly that " On the Forces of Inorganic Nature/' would, 

 I am sure, interest many of your readers, and enable them to 

 fully appreciate his just claims. 



I remain, Gentlemen, 



Yours respectfully, 



J. P. Joule. 



XVI. On some of the Basic Salts of Copper. By Frederick 

 Field, F.R.S.E., Professor of Chemistry at the London Insti- 

 tution*. 



T2ASIC Sulphate of Copper. — The analyses of this compound, 

 made from time to time by chemists, are not very con- 

 cordant, the oxide of copper varying in some instances as much 

 as 3 per cent, in different estimations, causing the formula of the 

 salt to range between 4CuO, SO 3 , 4HO, and 4CuO, SO 3 , 3HO. 



These discrepancies may partly be accounted for by the differ- 

 ent modes adopted for the preparation of the substance ; as some- 

 times it is formed by the digestion of the hydrated oxide, or 

 basic carbonate, in a solution of the monosulphate, and at others 

 by the imperfect precipitation of the latter salt by the caustic 

 alkalies. Graham observes that, when formed by precipitation, 

 it is impossible to remove the last trace of sulphate of potash, 

 even by prolonged washing, this salt being carried down with 

 the precipitate. 



The mineral Brochantite has also been examined with much 

 care; and although the results differ slightly, it may certainly 

 be regarded as quadribasic, associated with four atoms of water. 

 A very pure sample, containing no earthy admixture or any trace 

 of carbonate, from Andacollo, Chile, differs but little from a spe- 

 cimen from Mexico, analysed by Berthier. 



Mexico (Berthier). Chile (Field). 

 Oxide of copper . . 66*20 66*94 



Sulphuric acid . . . 16*60 16*59 



Water 17*20 16*4 7 



100*00 100-00 



The specific gravity of the specimen from Chile was 3*81. 



* Communicated by the Author. 

 K 2 



