May 12,1923 Injury to Foliage by Arsenical Spray Mixtures 
503 
COPPER ackto-arsenit:^ (paris green) 
PREPARATION 
Copper aceto-arsenite is a compound of copper, arsenic, and acetic 
acid, Cu(C2H302)2.Cu3As20o, and theoretically contains 58.65 per cent 
arsenious oxid (AS2O3), 31.29 per cent copper oxid (CuO), and 10.06 
per cent acetic acid, C2H4O2. In the process of manufacture ver¬ 
digris and arsenic txioxid are the essential materials. Generally 
verdigris is dissolved in acetic acid and added to a boiling solution of 
white arsenic and allowed to stand for some time to completely precipi¬ 
tate the copper aceto-arsenite. The light green precipitate is then 
thoroughly washed with hot water to remove the soluble salts. 
Copper aceto-arsenite has several synonyms, the most important of 
which are Paris green, Schweinfurt green, and emerald green. The com¬ 
pound was discovered in 1814 during the course of experiments, with the 
object of preparing an improved Scheele's green or arsenite of copper for 
use as a coloring pigment in the arts. It is supposed to have been first 
made at Schweinfurt, Germany, but by whom is not recorded. On 
account of its poisonous nature its use as a pigment was limited, and at 
present it is scarcely used at all for this purpose, but has become one of 
the standard insecticide compounds, not only in this country but abroad. 
USE AS AN INSECTICIDE 
The history of the use of Paris green as an insecticide may be traced 
back to the period when the Colorado potato beetle became recognized 
as being of economic importance. The first published account of the 
destructive propensities of this beetle may be found in the Prairie Farmer, 
August 29,1861, (7) and Paris green appeared upon the scene at some time 
between i860 and 1870, but who first suggested it and who first used it 
for the destruction of the potato beetle will perhaps never be told. The 
use of this material as a standard insecticide undoubtedly began in the 
West Central States. At first the poison was applied in the powdered 
form, using flour, plaster, or ashes as a diluent. In 1872 Le Baron (jj, 
p. 116), State entomologist of Illinois, in referring to the spring canker- 
worm, recommended that— 
strong washes, such as Paris-green water, or suds made from whale-oil soap, thrown 
upon the trees with a garden syringe, will also materially check their depredations. 
This is probably the first statement in which the s)^nging or spraying of 
apple trees with Paris green is recommended. The first statement 
referring to the successful control of codling moth by the use of Paris 
green that attracted attention and which was followed by close investi¬ 
gation, appears to have been made by Edward P. Haynes (Lodeman, 
16y 1910) in 1878. After spraying his orchard with Paris green he 
said that it not only rid the orchard of cankerworms but the apples on 
the sprayed part were much less eaten by codling moths. However, the 
use of this poison for the destruction of foliage-eating insects was for 
various reasons adopted slowly, and it was not until about 10 years later 
that Paris green was freely recommended as one of the most valuable 
insecticides for the destruction of chewing insects. 
FERROUS ARSENATE 
The use of arsenate of iron as an insecticide in this country is in an 
experimental stage and this compound has been used to only a limited 
extent. 
