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 

 millimeters 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 lfi 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 (5). 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 wormseed oil 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 



8 G. 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 

 takes 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, so that including this in the determination of ascaridole means that only a small error is 

 introduced, amounting to probably 4 or 5 per cent. I found that in order to get good results with this 

 method the acetic acid solution must be 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 be fresh." 



