196 M. Benelius on the Combinations of [Sept. 



129*4 parts of sulphate of copper by saturating 100 parts of the 

 salt with sulphuric acid, expelling the excess of acid by evapo- 

 ration, and exposing the dry mass to a low red heat. This 

 corresponds with 64-36 peroxide of copper. A different quan- 

 tity of the same salt, decomposed by hydrate of barytes in the 

 manner described in the analysis of the sub-salt, yielded 63 per 

 cent, of sulphate of barytes, equivalent to 27 # 6 per cent of acetic 

 acid. For the water, therefore, there remains 8*04 per cent. 

 The oxygen of the oxide of copper is 12-98, of the acetic acid 

 12-97, and of the water 7"15 ; consequently, the acid and base 

 contain equal quantities of oxygen, and the water contains half 

 as much as the oxide. The composition of this salt is therefore 



By experiment. By calculation. Atoms. Mult, ofoxy. 



Peroxide of copper . . . 64-36 .... 64-82 .... 3 .... 2 



Acetic acid 27-60 27-83 2 2 



Water 8-04 7-35 3 1 



If the salt contained 4 atoms of water, in which case it might 

 be regarded as composed of 1 atom of neutral anhydrous 

 •acetate of copper, and 2 atoms of hydrate of peroxide of cop- 

 per, the quantity of oxide would amount only to 63-27 percent.; 

 but in the analysis both of this specimen of the salt, and of 

 others prepared on different occasions, I have invariably ob- 

 tained more than 6i percent, of peroxide of copper. At the 

 commencement of my examination of this salt, I felt disposed to 

 suspect that the differences' of colour which it exhibits might 

 be occasioned by a compound of this nature with hydrated per- 

 oxide of copper, which would probably possess a blue colour, 

 and that, on the contrary, the green variety might be nothing- 

 else than an ordinary sub-salt. But experiment does not appear 

 to corroborate this conjecture. 



If a boiling hot solution of acetate of copper be mixed with 

 caustic ammonia so long as the precipitate continues to be 

 redissolved, and if after this treatment it be kept for some 

 hours in a temperature of about 140°, there is deposited a blue 

 crystalline salt, agreeing in composition with the preceding. 

 If the liquid be now allowed to cool, it deposits the neutral 

 acetate in crystals, and the soluble sub-salt in a cohering 

 spongy uncrystallized mass. 



If a solution of the neutral salt be precipitated by caustic 

 ammonia, with the precaution that the whole of the acetic acid 

 shall not be combined with the alkali, we obtain a green 

 coloured gelatinous substance, which after having been washed 

 becomes light blue coloured, but is never in the slightest degree 

 crystallized. Towards the conclusion of the washing, alcohol 

 must be employed in place of water, otherwise it will become 

 black. This compound does not swell up when put into water, 

 a property which seems to belong peculiarly to the crystalline 



