THE ALCOHOLIC EXTRACT OF PYRETIIRUM. 
175 
was equally efficacious, aud even at the rate of 1 to 40 it killed two- 
thirds 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 llask about 4 ounces of insert -powder, and added about 
balf a gallon of alcohol; corked, and allowed to stand for SM hours. 
I then perforated the cork and introduced a glass babe, one-fourth of an inch in 
diameter and :5G inches long ; then subjected the lla-k to t he well regulated heat of 
a water-hath, not allowing the temperature to reach tho 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, aud, before neing, diluted with water, as 
shown in the experiments mentioned farther on. Subsequently I shook up the solid 
residue of the insect-powder with tho extract, and diluted the whole with water, 
and in applying kept the solid mutter 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 of 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 06 ]«t 
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. 
Tho 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 2<» pints (*JA gallons) wood-spirit : this can be 
safely diluted in the earlier part of the season, when the worms are small, with 40 
parts of water; hence, 1 pound pyrethrum and 21 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 *1. ;"><»; 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. 
w hen the extract is to bo used for Boll Worms that are working on the contents of 
the bolls. By its ready volatilization it distributes ihe insecticide rapidly into the 
adjacent air, and when not directly thrown into the hole ent by the Boll Worm it is 
carried into the chamber by rapid diffusion, and, affecting tho 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, aud 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. 
