o/" Copper and of Iron. 305 



could not pven thus procure, in a ftate conftantly fimllar, 

 the -fait I wKhed to examine. The only conclufion which all 

 thefe experiments entitled me to draw, was that, in the firft 

 inflance, water precipitated the muriate of this particular ox- 

 ide of copper from its folution, but in a manner very different 

 from that in which muriate of antimony, of bifmuth, and 

 fome other metallic falls are a6l:ed upon. When into either 

 of thefe niiirjatcs water is poured, a precipitate enfues, but it 

 retains a very fmall portion of acid, if any ; whereas, in the 

 cafe before us, it is a fait, and not an oxide of copper, that 

 is thrown down. In order to etfeiSt in this fait a decompofi- 

 tion fimilar to that which takes place in muriate of bifmuth, 

 or of antimony, it is neceffary to draw off the firft liquor, and 

 then proceed to wa(h copioiifly. The precipitate will by de- 

 grees aflume an orange colour, which, as we fhall prefently 

 fee, is the real appropriate colour of this oxide of copper, 

 prepared in the humid way. 



It is evident alfo, from this precipitation, that this oxide 

 of copper combines with muriatic acid by a very (lender af- 

 finity. 



As it did not appear to me, that I fliould obtain any thing 

 verv fatisfadorv from this combination with muriatic acid, £ 

 refolved to try fome other acids. Sulphuric, pbofphoric, ox- 

 alic, citric, acetic, tartareous, and acetous acids w^^re each 

 poured upon known quantities of the ore, and kept in bottles 

 completely filled and well flopped, in order to prevent any 

 abforption of atmofpheric oxvgen. The liquors generally 

 became blue ; and, upon trial, were found to contain the 

 common and well knewn falts of copper, compofed of the 

 tefpeitive acid, and the oxide of copper containing 20 per 

 cent, of oxvgen ; while a large portion of the ore appeared to 

 remain in its original ftate. But, as I was certain that there 

 could be no dccompofuion in moil of thefe acids, under the 

 above circumftances, and moreover, that no oxygen could be 

 taken in from the atmofjfliere, it became a matter of no fmall 

 intercll to examine from what fource the nietal diflblved had 

 acquired the neceirary quantity of oxygen to favour its folu- 

 tion, and aiford tlie u'fual laltof copper, \n which it is oxidated 

 in the proportion of 20 per cent. 



I repeated, with all the above acids, the experiments tend- 

 ing to fatisfy that inquiry ; but, as the refults from ail were 

 nearly (iuiilar, I Hiall mention that only which proved to be 

 the uioft ample and the molt conclufive. 



One hundred parts of the pulverized ore were introduced 

 into a fmall phial, and dilute pholphoric acid was jiourtd in, 

 fo as to fill it. A grouad-ftoppcr clofed il complctclv j and 



Vox.. XII. No. 4«. U ia 



