1884. 1 
its Properties and Manufacture. 469 
becomes crystalline, and acquires the fine green colour 
peculiar to the aceto-arsenite.” I do not know from personal 
knowledge, but I have always understood that the copper 
salt employed in its manufacture in France is the acetate. 
This would account, in my opinion, for the larger crystalline 
flakes in which it is obtained in France than can be produced 
by the English method of manufacturing it. Cupric acetate 
is never employed, I believe, in England,— the much cheaper 
copper salt, the sulphate, being always employed. 
In “ Miller’s Chemistry ” it is stated it “ may be obtained 
by boiling solutions of arsenious anhydride and cupric 
acetate, and adding to the mixture an equal bulk of cold 
water.” Why it should be recommended to add cold water, 
I am at a loss to understand. 
In Drs. Roscoe and Schorlemmer’s large work on 
“ Chemistry,” and in the English edition of “ Wagner’s 
Handbook of Chemical Technology,” edited by Mr. Crookes, 
the process as described by Dr. Ehrmann in the “ Ann! 
Pharm.,” xii., 92, is given. It is thus stated in Wagner’s 
work: “This pigment is prepared by first separately dis- 
solving equal parts, by weight of arsenious acid and neutral 
acetate of copper in boiling water, and next mixing these 
solutions while boiling. There is immediately formed a 
flocculent olive-green coloured precipitate of arsenite of 
copper, while the supernatant liquid contains free acetic 
acid. After a while the precipitate becomes gradually 
crystalline, at the same time forming a beautiful green pig- 
ment, which is separated from the liquid by filtration, and 
after washing and carefully drying is ready for use. ’The 
mode of preparing this pigment on a large scale was 
originally devised by M. Braconnot, as follows : — 15 kilos, 
of sulphate of copper are dissolved in the smallest quantity 
of boiling water, and mixed with a boiling and concentrated 
solution of arsenite of soda or potassa, so prepared as to 
contain 20 kilos, of arsenious acid. There is immediately 
formed a dirty greenish coloured precipitate which is con- 
verted into Schweinfurt green by the addition of some 
15 litres of concentrated wood-vinegar. This having been 
done, the precipitate is immediately filtered off and washed.” 
As I have already stated, the copper salt used in the 
manufacture of this pigment in England is the sulphate, and 
it is carried out pretty much according to Braconnot’s me- 
thod as described by Dr. Ehrmann ; but anyone would infer 
from reading his description of the manufacturing process, 
that the compound, aceto-arsenite of copper, was formed 
almost immediately after the addition of the acetic acid, a 
