14 
BULLETIN 1332, U. S. DEPARTMENT OF AGRICULTURE 
with 20 cubic centimeters of carbon disulfide and adding N/10 
KOH or N/10 NaOH until tbe solution is about neutral to phenol- 
phthalein, 10 cubic centimeters of the hydroxide being ordinarily 
required. 
Theoretically, about 18.3 cubic centimeters of N/10 potassium or 
sodium hydroxide is required to neutralize 0.5 cubic centimeter of 
oleic acid, but in tests by mixing the acid with carbon disulfide it 
was found that only 10 cubic centimeters of N/10 hydroxide was 
required. This may be due to the solvent action of the carbon 
disulfide upon the oleic acid, thus limiting the necessary neutralizing 
action of the potassium hydroxide on the oleic acid at the surface of 
the carbon disulphide globules, the acid in solution in the interior of 
each individual globule probably not being acted upon. The neces- 
sity for less than the theoretically correct amount would naturally 
result from this condition. 
In the case of both of these carbon-disulfide emulsions water is 
the external phase and carbon disulfide the internal phase, with a 
hydrophile colloid as the emulsifier. 
Carbon-disulfide emulsion was tested along three lines: (1) Larvae 
(not in soil) were submerged in the dip for various periods, to deter- 
mine the time necessary at various temperatures for the dip to be 
completely effective. (2) Peony roots infested with larvae were 
dipped for various periods to determine the toxicity of the material 
to the larvae under natural conditions and the resistance of the plant 
to the insecticide. (3) The method was tested out under commercial 
conditions involving the treatment of the entire croD of one of the 
local nurseries. 
TOXICITY OF CARBON-DISULFIDE EMULSION TO LARVAE 
Larvae free from soil were dipped in dilutions of the carbon- 
disulfide emulsion at different temperatures and for different 
periods of treatment and the results noted. Two dips were used, one 
of 4.2 cubic centimeters of emulsion 1, and the other of 4.57 cubic 
centimeters of emulsion 2, each to 6 liters of water. The results for 
the two were not separately recorded, the preference being slight. 
The results in larvae killed for different temperatures and periods of 
exposure are presented in Table 8. It is evident that the optimum 
temperature lies between 60° and 70° F., the latter being preferable, 
and that much of the effectiveness of the dip depends upon a tempera- 
ture not too low. 
Table 8. — Toxicity of carbon-disulfide emulsion to larvae of the Japanese beetle 
(not in soil) l 
Temperature of dip (° F.) 
Percentage of larvae killed by immersion in dip for hours specified 
3 
4 
5 
6 
7 
8 
9 
12 
15 
18 
21 
24 
50 
25 
100 
100 
100 
25 
100 
100 
100 
50 
100 
100 
100 
75 
100 
100 
100 
100 
1C0 

75 
100 
50 
100 
75 
100 
100 
100 
100 

70...... 
1 The larva were Immersed for the specified time, and the percentages of those killed are tabulated . A 
total of aboul ion larvae were used in these tests. 
