I. CG. C. LARVICIDE 3885 
“A number of experiments were carried out for the purpose of obtaining a 
cheap and efficient preparation for destroying mosquito larve. Crude petroleum 
oil was frequently too viscid to have a spreading pawer of the highest efficiency. 
When mixed with crude carbolic acid, however, its spreading powers were in- 
creased. From laboratory tests it was determined that crude petroleum for 
surface use on pools should not be heavier than —° Baumé (American standard). 
“Much of the crude carbolic acid supplied had been found upon analyses to 
consist chiefly of inert neutral oils with a small proportion, 5 to 10 per cent, 
of tar acids, and, as this crude acid was used extensively as a disinfectant, ex- 
periments were conducted for the purpose of utilizing, if possible, this crude 
carbolic acid as a disinfectant and larvacide. It was found that crude carbolic 
acid, having a specific gravity not greater than 0.96 or 0.97, and containing 
about 20 per cent of phenols or tar acids, when made into a soap, with common 
resin and an alkali, yielded a product which was an ideal larvacide, having ex- 
cellent diffusing and toxic powers, and at the same time was a very efficient 
germacide. It diffused perfectly with water, forming a milky emulsion very 
destructive to mosquito larve, and having a germicidal value of, or greater 
than, that of pure carbolic acid of a Rideal-Walker coefficient of 1 to 2. In this 
way a very valuable larvacide and disinfectant, miscible with water, was pro- 
duced from a very inferior insoluble disinfectant. 
“ The larvacidal powers, when tried with Culex and Anopheles larve, varied 
slightly with the quality of the crude carbolic acid, but an average result is as 
follows: 
“Dilution 1 to 1000: Culex larve dead in five minutes 
Anopheles larve, half grown, dead in five minutes. 
Anopheles larve, full grown, dead in ten minutes. 
“Dilution 1 to 5000: Anopheles larve, half and full grown, dead in five 
minutes. 
Culex larve, half grown, dead in three minutes. 
“ Dilution 1 to 10,000: Culex larve, half grown, dead in sixty-four minutes. 
Anopheles larve, young, dead in fifty-two minutes. 
Anopheles larve, full grown, dead in one hundred and 
thirty-five minutes. 
“Dilution 1 to 15,000: Small Culex larve, dead in thirty-two minutes. 
Anopheles larve, full grown, dead in one hundred and 
twenty-three minutes. 
“ Anopheline larve seem to be slightly more resistant than Culex larve, and 
all pupe are more resistant to the effects of the larvacide than larve are.” 
As the result of the experimental work with larvicides Colonel Gorgas and 
his assistants have constructed a larvicide plant at Ancon, and in the monthly 
report of the Department of Sanitation of the Isthmian Canal Commission for 
August, 1909, it is stated that 14,600 gallons of larvicide were made at a cost 
of $0.1416 per gallon. The method of preparing this larvicide is quoted from 
this report: 
“The method of making same is as follows: 150 gallons of carbolic acid is 
heated in a tank to a temperature of 212° F.; then 150 pounds of powdered or 
finely broken resin is poured in. The mixture is kept at a temperature of 212° 
F., 30 pounds of caustic soda is then added and solution kept at 212° F. until 
a perfectly dark emulsion, without sediment, is obtained. The mixture is 
thoroughly stirred from the time the resin is used until the end. 
“The resultant emulsion makes a very good disinfectant or larvacide. In 
fact 1 part of it to 10,000 parts of water will kill anopheles larve in less than 
