1824.] Acetic Acid with Peroxide of Copper. 195 



equivalent to 43-19 of oxide of copper. (In other experiments I 

 obtained from 86-6 to 86-8 of sulphate of copper, which gives a 

 similar result.) The oxide of copper and the acetic acid amount 

 together to 79-99, and 10 of water had been expelled in the 

 temperature of 140°; consequently 10-01 of water still remained 

 in combination, that is, the salt 'lost one half of its water of 

 crystallization, by the application of heat. 43*19 of oxide of 

 copper contain 8-71 of oxygen, and 36-8 of acetic acid contain 

 17-3 of oxygen, that is, twice the quantity of the oxide of cop- 

 per, for 8-71 x 2 = 17-42. The oxygen in the whole quantity 

 of water amounts to 17-78, in one half of the water, therefore, 

 it amounts to 8*89 ; a slight excess over the oxygen of the 

 oxide, which is occasioned undoubtedly by the presence of 

 some hygroscopic moisture. The salt, after having been ex- 

 posed to a temperature of 140°, is constituted therefore of 

 3 atoms of oxide of copper, 4 atoms of acetic acid, and 6 atoms 

 of water. The salt, before exposure to heat, contains 12 atoms 

 of water, and is composed of 



By experiment. By calculation. Atoms. Mult, of oxy. 



Peroxide of copper ..43-19 .... 43*24 .... 3 .... 1 



Acetic acid 36-80 .... 37-14 .... 4 2 



Water 20-01 .... 19-62 .... 12 .... 2 



The insoluble Sub-salt.— This compound may be prepared by 

 allowing verdigris to swell up in water, and afterwards filtering- 

 it through coarse linen, which retains any impurities which may 

 have existed in the verdigris, but allows the minute scaly 

 crystals to pass freely between its threads. The crystalline 

 scales are now to be separated by pouring the whole of the 

 filtered portion upon fine cambric. They should be pressed 

 closely together and washed a few times with water; after this, 

 they should be transferred upon a paper filter, and thoroughly 

 washed with alcohol. When obtained in this manner, they 

 constitute a mass of small light blue shining crystalline scales, 

 having a deeper and purer blue colour, than the preceding solu- 

 ble sub-salt. Dried in a temp, of 212°, they lose only an incon- 

 siderable quantity of hygroscopic water, and sustain no altera- 

 tion in their appearance. When put into water, they swell up, 

 as happens with verdigris, into a pasty mass. 



Calcined in a balanced porcelain crucible, this salt left 64*25 

 per cent, of its weight of peroxide of copper. This calcination 

 can be advantageously accomplished only when the sub-salt is 

 in the state of hard lumps, and when the crucible is covered 

 pretty closely with its lid until the whole of the acid be 

 expeiled : unless these precautions be attended to, the combus- 

 tion of the mass is accompanied with slight detonations, and 

 a portion of the oxide of copper is carried off mechanically by 

 the disengaged gases. In another experiment, I obtained 



o2 



