1824.] Acetic Acid tvith Peroxide of Copper. 193 



intense dark blue colour ; but it is difficult to wash the inso- 

 luble portion thoroughly by this means, because the crystals 

 speedily close up the pores of the filter. If verdigris be washed 

 with water for a number of times in succession, the filtered 

 liquid continues to retain its original intensity of colour ; a 

 proof, that it extracts to the last a compound which requires 

 for solution a large quantity of water. This circumstance, 

 together with the blue colour of the liquid, demonstrates suf- 

 ficiently, that the solution does not contain merely the neutral 

 salt, as has been stated by Phillips. When the blue liquid is 

 heated almost to ebullition, it lets fall a flocky liver-brown 

 coloured substance ; after this it becomes green, and holds in 

 solution the neutral salt. If, on the contrary, the blue liquid 

 be evaporated in so moderate a heat, that it shall never appear 

 brown, which is easily done, so long as it continues dilute, it 

 deposits on the sides of the vessel, just at the edge of the 

 solution, a confused blue coloured saline mass, of a peculiar 

 dendritic appearance : the same salt accumulates on the edges 

 of the filter, and shoots up into moss-like excrescences. By 

 allowing this gradual evaporation to proceed to a state of dry- 

 ness, the blue saline mass is also obtained, but mixed with crys- 

 tals of the green neutral salt. 



After the washing of the insoluble portion of the verdigris 

 has been protracted for a considerable length of time, the liquid 

 at last passes through colourless ; and there remains upon the 

 filter a blue coloured powder, which has usually a blackish 

 tint, where it lies immediately in contact with the paper. Hence 

 it follows that cold water converts verdigris into three distinct 

 salts, namely, into the neutral acetate of copper, and into two 

 sub-salts, one of which is soluble and the other insoluble in 

 water. Verdigris when diffused through a small quantity of 

 hot water does not become black. The solution has a dark 

 blue colour, and contains a large quantity of the soluble sub- 

 salt ; on cooling, nearly the whole of this compound separates 

 in the state of a blue coloured mass, which does not exhibit 

 the slightest indications of crystallization. If the verdigris be 

 boiled with a large quantity of water, it is rendered brown ; and 

 in proportion as the quantity of water employed for this pur- 

 pose is augmented, the lower is the temperature necessary to 

 produce this alteration, so that when the water is in great 

 excess, it may be completely effected in a temperature so low 

 as 104° (Fah.) In this experiment there is formed a brown sub- 

 salt with a great excess of base, and the solution, provided it 

 be very dilute, contains even a quantity of unconibined acetic 

 acid, mixed with the neutral salt. 



The Sub-salt soluble in Water. — This salt may be prepared in 

 the following manner : — a. A solution of verdigris in distilled 

 wiiter is to be concentrated in a very gentle heat, until tlir 



New Series, vol. viu. o 



