4 BULLETIN 1332, U. S. DEPARTMENT OF AGRICULTURE 
ascaridole, suffers a molecular rearrangement when heated to 150° C. 
Consequently, if a vacuum of not over 6 millimeters is employed and 
the heat of the bath regulated the temperature of the oil need never 
be brought near 150° C. and the danger of explosion, owing to sudden 
molecular rearrangement of ascaridole, is virtually eliminated. 
Practically all of the first fraction up to 80° C. will consist of terpenes ; 
the next "fraction, which is ascaridole, boils at about 95° C. at 6 
milhmeters pressure, and the residue in the distilling flask contains 
some resinified products and considerable ascaridole glycol. To 
obtain pure ascaridole it is sometimes, in fact almost always, neces- 
sary to refractionate the ascaridole fraction. 
The principal constituent of the oil, ascaridole, C 10 H ie O 2 , has a 
specific gravity of 1.0024 at 25° C, a disagreeable, benumbing odor, 
and a disagreeable taste. Ascaridole (so called because of its action 
against Ascaridae) is generally conceded to be the active ingredient 
of the oil, although some investigators state that the terpenes and 
the residue containing ascaridole glycol are also active. The writers 
have done some work on this point, with results reported later in 
this bulletin (Table 6). 
Inasmuch as ascaridole is essentially the active ingredient of 
wormseed oil from the standpoint of toxicity toward insects, it is well 
to purchase the oil on the basis of ascaridole content rather than on 
that of price. A lot of oil containing 45 per cent of ascaridole at 
$2.50 a pound is not as economical of the money invested as another 
lot of oil containing 65 per cent of ascaridole and priced at $3, since 
the concentration of the dip for the control of the Japanese beetle 
larva is based on ascaridole and not on wormseed oil. 
Under these circumstances it is advisable before buying oil in 
quantity to determine the ascaridole content by means of the method 
devised by Nelson (o). In a cassia flask, the neck of which holds 10 
cubic centimeters, graduated in tenths, agitate thoroughly 10 cubic 
centimeters of the wormseed oil to be tested with 60 per cent acetic 
acid, made by mixing 60 parts by volume of glacial acetic acid with 
40 parts of water. The flask is then filled to the mark with 60 per 
cent acetic acid and allowed to settle. The volume of undissolved 
oil is deducted from 10; the remainder, multiplied by 10, gives the 
volume percentage of ascaridole in the sample. 5 
Wormseed oil is but very slightly soluble in water, and for that 
reason an aqueous solution of it has very little promise as a dip for 
the control of the Japanese beetle larva. Under the circumstances, 
probably the only practical method of regulating the concentration 
of oil in the dip is to make an emulsion of the wormseedVil which, 
when added to the water, will disperse evenly. 
WORMSEED- OIL EMULSIONS 
Since this emulsion must be one that will disperse in water, it 
follows that water must be the external phase and wormseed oil the 
* Q. A. Russell, in a letter to the writers, makes the following observations on this method of ascaridole 
assay: "This method is only approximate, but no other method is known. The 60 per cent acetic acid 
take.-, into solution any ascaridole glycol present in the oil, and thus the apparent percentage of ascaridole 
is Increased. In well-prepared oils which are comparatively fresh the ascaridole glycol is present only in 
small amounts, BO that including this in the determination of ascaridole means that only a small error is 
introduced, amounting to probably t or ."> per cent. I found that in order to get good results with this 
method the acetic acid solution must he made up fresh, using glacial acetic acid Which has not stood in 
partly-filled containers for any length of time. That is the acetic acid should he fresh." 
