-10- 
Garnett ( 169 ) in 1935 described further studies on the insecticidal 
properties of derris-root residues extracted rath different solvents. 
Extractions v/ere made by continuous distillation in Soxhlet apparatus 
for about 10 hours. These solvents can be divided into two groups: 
(a) Water-soluble: Ethyl alcohol, acetone, and acetic acid; (b) water- 
insoluble: Ethyl acetate, carbon tetrachloride, benzene, chloroform, 
and ether. Successive or secondary extractions were obtained by re-extrac- 
ting the marc with the same or a different solvent. In some cases, the 
residue left on re-extraction was still further extracted with another 
solvent. The extracts v/ere used to determine the percentage of total ex- 
tractives present. The residues left after extraction and certain of the 
extracts v/ere tested on silk moth larvae. The following conclusions v/ere 
drav/n from the results: 
Ethyl alcohol v/as the only solvent which removed practically all 
the insecticidal substances from the root, leaving a residue v.hich 
produced slight, if any, effect on silkworms or aphids. All the 
marcs tested, exerted a deterrent effect on silkv/orms. 
• 
The percentage of total extractives obtained from derris root 
varies with the type of organic solvent used. Water-soluble solvents 
tend to extract more total solids from the root than do water-insol- 
uble solvents. However, the removal of a large percentage of total 
extractivos by a solvent does not alv.ays indicate more efficient in- 
secticidal extractive properties. 
Tests on insects with the marcs and with certain of the extracts 
indicate that the water- soluble solvents also extract more of the 
active insecticidal ingredients. 
Re-extraction with the same solvent after 10 hours* continuous 
Soxhlet extraction removes very little, if any, additional solids or 
insecticidal material from the root. 
Successive extraction with a water-soluble solvent (acetone or 
alcohol) of a residue previously extracted with a water-insoluble 
solvent (ether or carbon tetrachloride) removes additional insectici- 
dal constituents. 
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