The invention relates to a chemical dosing device for leaching a phosphorated chemical material impregnated in crystallised sand in a liquid, the resulting mixture thereof being dosed in a proportion of one part per million in a container of the liquid which will be treated with temephos in order to eliminate the fly larvae, said container comprising at least two perforations, wherein at least one of said perforations allows the inflow of the liquid into the dosing device and the rest allow the outflow of a substance resulting from the mixture of the phosphorated chemical material impregnated in crystallised sand, which, when leached, applies a mixture of one part per million of temephos which eliminates the fly larvae. The dual chemical dosing device has a functional characteristic as a result of the physical properties thereof, which is that it maintains a pendular movement inside the container of the liquid to be dosed, as a result of the float and the counter-weight which are components thereof, generating a more efficient dosage of the mixture obtained and therefore facilitating the process of treating a liquid contained in a recipient with a phosphorated chemical material impregnated in crystallised sand, which applies temephos in a proportion of one part per million according to the specifications of the WHO for the innocuousness of the pesticide that eliminates fly larvae when applied to water for human use and consumption.
