1824.] Acetic Acid with Peroxide of Copper. 199 



be difficult to decide with perfect certainty, whether its consti- 

 tution forms au actual exception to the law, or whether its 

 component parts may not be considered to be in conformity 

 with the law, but merely assoeiuied in more complicated com- 

 binations. 



I shall here, without however professing to attach to it any 

 particular importance, explain the view which I have endea- 

 voured to take of the constitution of this compound. I dried 

 100 parts of the pulverized blue verdigris in a steam bath in the 

 temperature of 212°, until it ceased to sustain any farther loss 

 of weight. The residue weighed 76*55 parts. The powder 

 had by this treatment diminished considerably in volume, and 

 had acquired a hue green colour. These 76*55 parts are com- 

 posed according to the preceding analysis of 



Peroxide of copper 43*34 containing oxygen 8*74 



Acetic acid 27*45 12*90 



Water 5*76 5*12 



The oxygen of the water possesses no determinate relation to 

 that of the oxide of copper: but if we suppose that the blue 

 variety of verdigris is resolved, in consequence of the separa- 

 tion of water, into neutral acetate, and insoluble sub-acetate, 

 (in which the acid saturates thrice as much base as in the neu- 

 tral salt,) both retaining their usual quantity of water of crystal- 

 lization, the mixture would consist of an atom of each, namely, 



Cu A 2 + 2 Aq 

 Cu 3 A- + 3 Aq. 



That is, the oxide of copper existing in it would contain 

 8 atoms of oxygen, and the water 5. Now 8:5:: 8*74 : 5*46. 

 That the experimental determination of the water falls some- 

 what short of the theoretic, is occasioned probably by all the 

 verdigris of commerce containing; a slight admixture of the inso- 

 luble sub-acetate. The calculation is of course made on the 

 supposition that the verdigris is in a state of complete purity. 

 It is therefure pretty certain, that a temperature of 212° alone, 

 without requiring the intervention of water, decomposes verdi- 

 gris into an atom of neutral, and an atom of sub-acetate. We 

 have also seen that water, both when cold and hot, is capable 

 of accomplishing the same alteration. It cannot be doubted 

 then, that in this compound the constituents are retained in 

 union by very feeble affinities. 



I at first conjectured, that, in the preparation of verdigris, 

 the accession of oxygen is so limited, that an acetate of pro- 

 toxide of copper only (Cu A) is in the first instance formed, 

 and that this compound, by absorbing oxygen from the atmo- 

 sphere, is gradually converted into a salt of peroxide, through a 



