22 
Bulletin 71. 
green is entirely soluble in ammonia, giving a clear blue liquid. If 
any particles can be seen floating through the liquid or settling to 
the bottom, the article is not pure. If the ammonia dissolves all, 
there can be little doubt that it is pure. This is a test that anyone 
can make. The particles of Paris green are entirely bright green in 
uolor and globular in form, and the presence of an adulterant can 
be most easily detected under a microscope of moderate power. 
Prof. Woodworth of the University of California explains another 
method by which impurities can usually be detected in Paris green. 
It is by placing a small amount of the poison on a clean piece of 
glass and then slanting the glass and jarring it so as to cause the 
powder to slide to the lower side. If this is done carefully the 
adulterants, which are not green in color, will fall behind and can 
be detected with the unaided eve. 
Where there are several persons in the same neighborhood 
wanting this poison, it is best for all to order together and then send 
a sample to a chemist for analysis. If a good number unite in this 
way the Station chemist, most likely, would be willing to make the 
test free. 
Application of Paris Green to Plants .—The arsenical mixtures 
are usually applied in a watery spray, and the most common 
strength is: 
Paris green. 1 pound 
Water.160 gallons 
Lump lime (freshly slaked). 2 pounds 
On very sensitive foliage, like that of the peach, apricot, nec¬ 
tarine and bean, it would be safer to use 200 gallons of water to a 
pound of the poison. A pound to 100 gallons is quite safe for appli¬ 
cations upon apple, cherry, cabbage, beets, potatoes, and most other 
trees and plants in the dry atmosphere of Colorado. The poison 
always should be placed in a small quantity of water first and 
thoroughly stirred in and then poured into the full amount of 
water to be used. 
The chief objection to the use of Paris green as an insecticide 
is its high specific gravity, which causes it to settle rapidly in 
water. Pumps used to apply this poison always should have some 
means of keeping the water well stirred. 
Dry applications may be made in various ways. Sometimes 
the poison is used pure, in which case the lightest possible dusting 
is made over the plants. It is usually better to dilute the poison 
with about twenty times its own weight of flour, plaster or lime, 
when a more liberal dusting may be made. This method is more 
economical of the poison and enables one better to tell when 
all parts of the plant have been treated. A good proportion is * 
Paris green... 1 pound 
Common flour...20 pounds 
