8 BULLETIN 1332, IT. S. DEPARTMENT OF AGRICULTURE 
Table 5. — Comparative toxicity of stock wormseed-oil emulsions of various ages 1 
Age of stock emulsions in days 
Percentage of larvae killed by immersion in dip for 
hours specified 
5 
6 
7 
8 
9 
10 
15 
1 . . ... 
50 
75 
100 
100 
75 
75 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
3 ...----.--- - 
100 
14 . - - 
100 
23 - .- - - 
100 
30 
100 
40 
100 
1 All the emulsions subjected to this test contained 1 cubic centimeter of ascaridole to 6 liters of water. 
The test was applied at a uniform temperature of 70° F. (21° C). A total of about 800 larvae were used 
in the tests on which this table is based. 
COMPARATIVE TOXICITY OF THE INDIVIDUAL INGREDIENTS OF WORMSEED OIL 
As already stated, wormseed oil when distilled under a vacuum 
of approximately 6 millimeters pressure can be separated by proper 
technique and control of temperature into three fractions consisting 
mainly of (1) terpenes, (2) ascaridole, and (3) a residue containing 
principally ascaridole glycol. However, in separating the oil into 
fractions for determining the toxicity of its several constituents, 
four fractions were made, of which the first consisted mainly of 
terpenes, the second of a mixture of terpenes and ascaridole, of 
which the terpenes constitute the major portion, the third of prac- 
tically pure ascaridole, and the fourth a residue consisting princi- 
pally of ascaridole glycol. Data on the relative toxicity oi these 
ingredients are presented in Table 6. G 
In making up the individual Crips for the tests, material from each 
fraction was emulsified with soap, using 10 cubic centimeters of 
soap, 10 cubic centimeters of water, and 20 cubic centimeters of the 
material, as was done with the wormseed oil in making the first 
and most satisfactory emulsion in testing the stability of emulsions, 
as recorded in Table 2. For each test to 6 liters of water was added 
3.67 cubic centimeters of the emulsion. It will be noticed that all 
the ingredients of the oil are toxic to the larvae. The ascaridole was 
completely fatal to larvae in 5 hours, the terpenes in 8 hours, and 
the residue in 12 hours. The results merely emphasize the fact 
already stated that in buying oil of wormseed it is advisable to 
purchase primarily on the basis of ascaridole content rather than on 
that of price. 
6 With respect to the ascaridole glycol of the fourth fraction, the following excerpt from a letter from 
Q . A Russeu, by whom it was fractionated and assayed, may be of interest: "I have never done any work 
on the keeping qualities of wormseed oil, but Nelson examined five samples of American oil which had 
b< en shipped to Brazil and subsequently returned to the United States, all of which were at least 1 year 
old. He found that the distillate residues, while higher than those found in fresh oil, were not excessive, 
and concluded from this that the oil does not deteriorate very rapidly with age. It is mv opinion that oil 
preserved in well-filled containers will keep without appreciable change for a period o*f at least 1 year. 
This glycol is formed b\ the rearrangement of the ascaridole molecules, and apparentlv is produced by the 
action of the steam on the ascaridole at the time of distillation. This may account for the high percentages 
of residue obtained when fractionating oils distilled by means of low-pressure steam over a relatively long 
period of time." 
