Emerald-Green : 
[August, 
468 
is a very stable compound not readily undergoing decom- 
position, and is consequently a very permanent colour. It 
has also been not unfrequently stated that the injurious 
effects of this pigment are due to the arsenious oxide 
volatilising from the other constituents of the compound. 
This volatilisation would likewise cause a breaking up of the 
entire compound, and would consequently cause a dis- 
colouration of the paper ; but the volatilisation of this 
arsenic compound is in every respedt most improbable. 
The injurious effedts, if any, of this pigment must there- 
fore be due to its mechanical detachment from the paper ; 
but has it ever been conclusively proved that persons who 
inhabit rooms the wall-paper of which is stained with 
emerald-green suffer from arsenical poisoning ? If it does 
occur, then the effedts of what may be termed homoeopathic 
doses of this substance are totally different from the effedts 
which arise from larger doses. During the packing of this 
substance in its dry state in the factory, clouds of its dust 
ascend in the air, and during the time I had to do with its 
manufadture I never heard that any of the fadtoiy hands 
suffered, nor did I suffer, from arsenical poisoning. If there 
is any abrasion of the skin the dust produces a sore, and 
also the delicate lining of the nostrils is apt to be affeaed. 
It is in this way it aas in large doses ; I am therefore very 
sceptical as to its supposed poisonous effedts when wall- 
paper is stained with it. 
Different methods are given in works on Chemistry for the 
manufaaure of this pigment, but as they do not agree in 
every respea with the method which was followed in 
English colour faaories some years ago, it will be as well, 
for the full elucidation of the manufaauie of this substance, 
to briefly recite some of these methods before describing the 
one that was, and probably is still, in use ; and I will alter- 
wards describe a method which i invented, and which is 
praaically superior to any other, both in the rapidity with 
which the colour can be formed, and for producing it at a 
less cost* 
It is stated in “ Watts’s Dictionary of Chemistry ’’ that it 
is “ prepared on a large scale by mixing arsenious acid with 
cupric acetate and water. Five parts of verdigris are made 
up to a thin paste, and added to a boiling solution of 4 parts 
or rather more of arsenious acid in 50 parts of water. The 
boiling must be well kept up, otherwise the precipitate 
assumes a yellow-green colour, from the formation of coppei 
arsenite : in that case acetic acid must be added, and the 
boiling continued a few minutes longer. The precipitate then 
