Measurement of insecticides for house spraying

In view of the economic and operational importance in malaria eradication campaigns of correctly measuring the insecticides used, tests have been made in Mexico to compare the accuracy of two manual procedures, one volumetric and the other gravimetric. For volumetric measurement a calibrated, metal measuring-can of sheet metal is used, and for gravimetric measurement a specially designed Roman balance. Altogether 1022 volumetric and 1411 gravimetric tests were made. The results, given in this paper, show that the volumetric measurement entails too great a margin of error to be acceptable, but that the Roman balance is both sufficiently accurate and practical and economical.