A spraying Apparatus and testing Chamber for investigating the residual Action of insecticidal Deposits

Abstract

The construction of a spraying tower for obtaining even deposits of insecticide of known weight is given, and the method of adjustment of this apparatus and procedure adopted during spraying are described.To determine the weight of deposit obtained with different liquids under various conditions of spraying, a colorimetric method of estimation was adopted. Deposits of dye solution were collected on test-papers disposed at different positions on the area sprayed, the dye dissolved in 50 cc. of solvent and the concentration of dye in this solution measured by means of the Spekker Photo-electric Absorptiometer. By this method estimations of the weight of dye deposited on each test-paper were made to 0·01 mg. with great rapidity. The solutions of dye used in these experiments were 1 per cent. wt./vol. solution of “Oil Golden Yellow 13777” in petroleum distillate and a 1 per cent. wt./vol. aqueous solution of “Orange 60506”.Series of tests were carried out with both the petroleum distillate and the aqueous dye solutions to determine the replication and distribution of deposits obtained with the spraying tower. It was found that the Standard Deviation of the mean weight of deposit per test-paper for the two spray liquids, both from one test to another and between different positions on the area sprayed in any one test, fell between ±0·8 per cent. and ±3·0 per cent. of the mean under the most favourable conditions for spraying.