THE ALCOHOLIC EXTRACT OF PYRETHRUM. 175 



was equally efl&cacious, and even at the rate of 1 to 40 it killed two- 

 tbirds of the worms upon which it was sprayed in 15 or 20 minutes, 

 and the remainder were subsequently disabled. In still weaker solu- 

 tion, or at the rate of 1 to 50, it loses in efficacy, but still kills some of 

 the worms and disables others. 



Professor Jones, of Oxford, Miss., reports his method of preparing 

 the extract, and the results of his experiments, made in 1880, as fol- 

 lows : 



In all my first preparations I proceeded as follows : 



I introduced into a glass flask about 4 ounces of insect-powder, and added about 

 half a gallon of alcohol; corked, and allowed to stand for 24 hours. 



I then perforated the cork and introduced a glass tube, one-fourth of an inch in 

 diameter and 36 inches long; then subjected the flask to the well regulated heat of 

 a water-bath, not allowing the temperature to reach the boiling point of alcohol. 

 I usually applied this gentle heat for about 5 hours ; then set aside to cool. At 

 first I decanted the extract from the residue, and, before using, diluted with water, as 

 shown in the experiments mentioned farther on. Subsequently I shook up the solid 

 residue of the insect-powder with the extract, and diluted the whole with water, 

 and in applying kept the solid matter suspended by agitation. I found the latter 

 plan economical. The residue, being wet with alcohol, readily spreads throughout 

 the water, and evidently adds something to the value (►f the extract. 



I have never seen any statement or suggestion in regard to the use of wood-spirit 

 as the menstruum. It occurred to me to try it. I found it to be a quicker solvent 

 of the essential oil and coloring matter of pyrethrum powder than common 95 per 

 cent, alcohol. I find that 1 pint and 2 ounces (by measure) of wood-spirit will ex- 

 tract all the useful material out of an ounce of pyrethrum. Good wood-spirit can 

 be bought for $1.25 per gallon. 



The extract made with wood-spirit will bear dilution with a somewhat larger 

 quantity of water than the extract made with ethyl alcohol. On this point I state 

 my results thus : 



One pound pyrethrum powder to 20 pints (2^ gallons) wood-spirit ; this can be 

 safely diluted in the earlier part of the season, when the worms are small, with 40 

 l^arts of water ; hence, 1 pound pyrethrum and 2^ gallons methyl alcohol will, when 

 diluted, make 100 gallons of liquid for the destruction of insects. Allowing 40 gal- 

 lons to the acre, the cost of this insecticide would be fl.50 ; with improved atomizers 

 this will be lessened. 



Wood-spirit is more volatile than ethyl alcohol. This, I think, gives it consider- 

 able advantage over ethyl alcohol as the solvent for the essential oil of the pyrethrum, 

 when the extract is to be used for Boll Worms that are working on the contents of 

 the bolls. By its ready volatilization it distributes the insecticide rapidly into the 

 adjacent air, and when not directly thrown into the hole cut by the Boll Worm it is 

 carried into the chamber by rapid diff'usion, and, aflecting the worm, causes it to 

 come forth from its concealment upon the moistened parts of the plants, where by the 

 contact of the liquid it is poisoned to death. The extract made with ethyl alcohol is 

 also volatile, and produces this same effect, though in a less degree, to the extent that 

 its volatility is less than that of methyl alcohol. The extractive power of methyl 

 alcohol on pyrethrum is so great that it is hardly necessary to apply any heat. The 

 alcohol may be allowed to stand 24 hours on the powder, being shaken up a few 

 times, and then the whole, both the extract and solid residue, may be mixed with 

 water, so as to give 100 gallons to the pound of pyrethrum. I found that the use of 

 the liquid is much to be preferred to the powder. It reaches all parts of the plant 

 better, it is more easily handled, and it kills quicker. 



