ON THE THEORY OF GALVANISM. 73 



fimilar to that of the cruft on the other fide of the copper. 

 This green cruft was fcarcely acted upon by water, but was 

 rapidly diflblved by ammoniac, and the folution became of a 

 deep blue colour. It feemed therefore to be a muriated oxide 

 of copper. The cryftals were only in part foluble in water, 

 the infoluble part became brownifh ; it was quickly diflblved 

 by ammoniac, and a deep blue was produced. The water in 

 which the cryftals had been digefted was without colour or 

 fmell, but upon the addition of a few drops of cauftic potafli, 

 it exhaled a ftrong odour of ammoniac. Thefe cryftals there- 

 fore appeared to confift of muriate of ammoniac united to a 

 quanti y of the oxide, or muriate of copper. The fides of the 

 glafs were lined with a coating of the green oxide, and as the 

 ammoniac continued to evaporate, the quantity of this oxide 

 was increafed. The fluid in which the copper had been di- 

 gefted exhibited alkaline properties, and was of a deep blue 

 colour; it contained the ammoniated oxide of copper. 3. A Exper. 3* ZJn t 

 piece of zinc and a piece of copper fimilar to thofe employed conta^nTa fi- 

 in the former experiments, were placed in a folution of the mHar folution} 



muriate of ammoniac in contact with each other. The zinc t Jt z ! ncon ywas 



acted on. 



was oxidated as in the former cafe, but the fluid remained co- 

 lourlefs, and the copper acquired no green cruft ; though after 

 being removed from the liquor and expofed for fome time to 

 the atmofphere, it gradually acquired a thin covering of oxide. 

 The liquor appeared to confift of muriate of ammoniac with a 

 fmall excefs of alkali. In this experiment we may conjecture, 

 that the zinc pofleffing a ftronger attraction for oxigen than the 

 copper, abftra6b it from the water, and the hidrogen which 

 is then difengaged either prevents the oxidation of the copper 

 from taking place, or reduces the oxide as quickly as it is 

 formed. 4. When the zinc and copper were placed in fepa- Exper. 4. Zinc 

 rate glafles of the folution of the muriate of ammoniac, and and C0 PP er e *- 

 the metals were connected by a filver wire, the zinc became but in feparate' 

 oxidated as ufual : the copper was in appearance fcarcely veflels, and corn- 

 acted upon, but the fluid acquired a blue tinge, which proves ™ lvei ! . ^'" e g t J* 

 that the ammoniated oxide of copper is formed, and confe- copper was little 

 quently that the muriate of ammoniac and water are decom- ^nce * jj * 

 pofed, and the copper oxidated, though thefe effects take zinc and copoer 

 place to a much lefs extent than in the fecond experiment. may , be ^ nfi " 



r r r dered as if one 



The general refults are favourable to our hypothefis. as we of the metals 



learn 



