May 12,1923 Injury to Foliage by Arsenical Spray Mixtures 
525 
A comparison of Tables IX and XIII leads to the conclusion that the 
addition of lime-sulphur and tobacco extract to arsenical spray mixtures 
has practically the same effect upon the foliage as lime sulphur alone. 
Arsenic trisulphid may constitute an exception, but our tests with this 
compound combined with both tobacco extract and soap are too few to 
be conclusive. It is doubtful, however, if the trisulphid will ever come 
into general use as an insecticide. 
hlMH SimPHUR, TOBACCO EXTRACT, AND SOAP 
This combination with arsenical compounds is not a desirable one as it 
often forms a curdled mass that is difficult to apply to the foliage. It 
also has a greater tendency to injure the foliage than any other combi¬ 
nation we have tried. Calcium arsenite in combination with these three 
substances is the only exception, as may be seen by Table XIV. 
Table XIV.— Effects of lime-sulphur^ tobacco extract, and soab upon the burning properties 
of various arsenical compounds 
Arsenical compounds to whidi lime- 
sulphur, tobacco extract, and soap 
were added. 
Number 
of brands. 
Number 
of appli¬ 
cations. 
Number 
of times 
injury 
increase. 
Number 
of times 
injury 
decreased. 
Number 
of times 
injury was 
the same. 
Number 
of times 
there was 
no injury 
with or 
without 
soap. 
Arsenic trioxids. 
2 
• 
5 
3 
I 
0 
I 
Arsenic disulphid. 
Arsenic trisulphids. 
I 
2 
2 
0 
0 
0 
2 
5 
5 
0 
0 
0 
Barium arsenate. 
I 
I 
0 
0 
I 
0 
Calcium arsenites. 
3 
17 
2 
8 
4 
3 
Copper aceto-arsenites. 
2 
20 
12 
2 
3 
3 
Ferrous arsenates. 
3 
8 
2 
I 
0 
5 
Lead arsenates, triplumbic.... 
8 
SI 
29 
0 
0 
22 
Lead arsenates, diplumbic. 
13 
84 
57 
0 
0 
27 
Lead arsenates, mixtiures. 
II 
30 
26 
0 
0 
4 
Zinc arsenites. 
6 
40 
17 
1 
1 
21 
gelatin, agar, and MIEK 
While soap is probably the best material known to make spray mixtures 
spread on leaves of cabbage, sugar beets, etc., where there is a tend^cy 
to roll off the smooth or waxy surface, its tendency to increase injury 
by most arsenical compounds gives an incentive to search for some other 
spreader. Moore {21) has given a very thorough discussion of the 
principles and practices of spreaders in spraying work, and a full bibli¬ 
ography of the subject. Gelatin, agar, and separated milk, having 
possibilities along this line, were tested in our work with v^ous arsenical 
compounds to determine ff they would influence the burning. 
The gelatin was used in strengths of o.i per cent and 0.4 per cent 
(i. e., I and 4 grams to the liter). The agar was used m strengths 
of o.oi and 0.04 per cent. The separated milk was used in strengths 
of o.i per cent and 0.4 per cent. Various arsenical spray mixtures, 
including lead arsenate, Paris green, and calcium arsenite, were tried 
singly and.in combination with these three “spreaders’* both on green¬ 
house plants and in the field, and also in the orchard. Repeated experi¬ 
ments showed no tendency on the part of these materials to increase 
the arsenical injury, and while they are not so efficient as soap in pro- 
