1884.] 
B in tv aid - Green . 
4 67 
IV. EMERALD-GREEN* : ITS PROPERTIES 
AND MANUFACTURE. 
By Robert Galloway, M.R.I.A. 
S j HE poisonous effects of wall-paper stained with emerald- 
l g re e n (aceto-arsenite of copper) appears to be a very 
favourite topic in many journals ; it is continually re- 
appearing in one form or another in different publications, 
especially medical ones ; there has recently appeared a short 
reference to it under the title, “ The Poisonous EffeCt of 
Wall-paper.” . As some years ago I became practically 
acquainted with its properties and manufacture, a few 
observations on these subjects may not be without interest. 
In the paragraph referred to, it is stated that the poisonous 
effect of this pigment cannot be entirely due to its mere 
mechanical detachment from the paper. This writer there- 
fore attributes the poisonous effects to the formation of the 
hydrogen compound of arsenic, viz., arseniuretted hydrogen 
(AsH 3 ) ; the hydrogen, for the formation of this compound 
being generated, the writer thinks probable, “ by the joint 
action of moisture and organic matters, viz., of substances 
used in fixing to walls papers impregnated with arsenic.” 
In some of our chemical manuals, Dr. Kolbe’s “ Inorganic 
Chemistry,” for example, it is also stated that arseniuretted 
hydrogen is formed by the fermentation of the starch-paste 
employed for fastening the paper to the walls. It is perfectly 
obvious that the fermentation of the starch-paste must cease 
aftei a time, and theiefoie the poisonous effects of the paper 
must likewise cease if its injurious effects are caused by the 
fermentation. I do not think that arseniuretted hydrogen 
could be formed under the conditions, for the oxygen com- 
pound of arsenic is in a state of combination, and the com- 
pound is in a dry solid state and not in solution, and the 
affinities of the two elements — arsenic and hydrogen for 
each other are so exceedingly weak that they cannot be 
made to unite direCtly except they are both set free at the 
same moment in presence of each other. Further, for the 
formation of this hydrogen compound by the fermentation of 
the starch, or by the growth of minute fungi, the entire com- 
pound must be broken up, and therefore the pigment would 
become discoloured ; but aceto-arsenite of copper — 
[ 3 CuAs 2 0 4 + Cu(C 2 H 3 0 2 ) 2 ] 
* This substance is also known by the name Schweinfurt green. 
