Abstract
A laboratory study was made on the effects of some metallic salts and cationic surface-active agents on the deposition of DDT emulsifiable concentrate sprays. An anionic surface-active agent, Atlox 3300® (isopropyl amine dodecyl benzene sulfonate), was used as the emulsifier for the DDT spray. The adjuvants were injected into the spray stream at various concentrations during the spraying operation. Beeswax- and collodion-coated glass vials were used as the standard surfaces for spraying. The total amount of spray deposit was determined by weight and the quantity of DDT by chemical analysis. The effectiveness of the metallic salts in increasing spray deposits was in the following order: FeCl3·6H2O>Pb (NO3)2>CaCl2·2H2O>ZnCl2>MgCl2·6H2O. The effectiveness of cationic surface-active agents was in the following order: Armac 18D® (acetic acid salts of fatty amine) >Armac C® (acetic acid salts of fatty amine)>Hyamine 2389® (methyl dodecyl benzyl trimethyl ammonium chloride) > CTAB (cetyl trimethyl ammonium bormide) >Emcol E-607® N-(laurol colaminoformylmethyl) pyridinium chloride> Arguad 12-50® (alkyl quaternary ammonium chloride) > Ethomeen C/15® (ethoxylated tertiary amine). The change in dynamic surface tension was related to spray deposit, i.e., the adjuvants which increased the dynamic surface tension also increased the amounts of spray deposit. A converse relation was also demonstracted. When water and xylene were emulsified with the anionic surface-active agent, an oil-in-water type of emulsion was formed. With the exception of Ethomeen C/15, the addition of adjuvants produced an inverted type of water-in-oil emulsion. In the case of the cationic surface-active agents, further addition reverted the water-in-oil to an oil-in-water type of emulsion. The adjuvants reacted with the DDT emulsion spray to form a precipitate and the adhesive quality of this precipitate appeared to influence the quantity of the spray deposit. The nature of the sprayed surface also influenced the quantity of the deposit, the amount being lower on a collodion than on a beeswax surface.
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