202 Combi nations of 'Acetic Acid with Peroxide of Copper. [Sept. 



is 18-55. 5-6 parts of sulphate of barytes are equivalent to 2-45 

 parts of acetic acid, whose oxygen is 1*151; but 1*151 x 16 = 

 18-416. For the water there remains 5*65, whose oxygen is 

 4*934 : this again is only a very little more than four times the 

 oxygen of the acetic acid, or one-fourth of that of the peroxide 

 of copper. This salt is therefore composed of 



By experiment. By calculation. Atoms. 



Peroxide of copper .... 92-00 92-30 24 



Acetic acid 2-45 2-44 1 



Water 5-55 6-26 12 



The following is a summary of the results to which J have 

 been conducted by the experiments detailed in this memoir. 



1. Acetic acid is capable of combining with peroxide of cop- 

 per in the following proportions : 



1. Neutral acetate of peroxide of copper = Cu A- + 2 Aq 



2. Blue verdigris = Cu A + 6 Aq 



3. Soluble subsalt = Cu 3 A 4 + 12 Aq 



4. Insoluble subsalt = Cu 3 A- + 3 Aq 



5. Black or brown subsalt = Cu- 4 A + 12 Aq 



If the quantity of base in the neutral salt be regarded as unity, 

 its quantity in the others, when compared with the same quantity 

 of acid, will be found to constitute multiples of the unit by the 

 numbers H, 2, 3, and 24 (48 ?). In the first salt, the base is 

 combined with twice as much acid as in the second ; and in the 

 third, with twice as much as in the fourth. 



2. Of all these salts the second has the simplest composition, 

 and consists, if the calculation be made directly from the weight 

 of its component parts, of the simplest number of atoms; but it 

 possesses a property which is directly contradictory of this sup- 

 posed simplicity of constitution, for its ingredients are retained 

 in union by weaker affinities than in any of the other combina- 

 tions of acetic acid and peroxide of copper, and have a greater 

 tendency to separate, and to recombine in other proportions. A 

 temperature of 140° decomposes it, with the loss of a portion of 

 its chemically combined watei, into an atom of the first and an 

 atom of the fourth salt. A sufficient quantity of cold water 

 decomposes it into an atom of the first, an atom of the third, and 

 two atoms of the fourth salt; and a sufficient quantity of boiling 

 water decomposes it into a large number of atoms of the first 

 salt, and a very few of the fifth. From all these circumstances, 

 together with this, that in the salt the oxygen of the acid is 

 not a multiple by a whole number, but by 1 -J- of the oxygen of 



