Dilead arsenate, largely on account of the fact that it is very slightly soluble in water, is extensively employed as an insecticide for use on plants. Notwithstanding the fact that this lead arsenate is but very slightly soluble in water, its use often produces serious burning when applied to tender foliage. Although this is due in many cases, as shown by Headden,1 and Haywood and McDonnell,2 to the decomposition of the lead arsenate by dissolved salts in the water used in applying the material, still burning of the foliage has been noted even when the water employed was pure. Volck3 states that lead hydrogen arsenate may be completely transposed to trilead arsenate by the prolonged action of fog, dew and rain. Tartar and Robinson,4 however, were unsuccessful in their endeavor to verify Volck's statement. On account of the divergence of opinion on the subject, and in view of its economic importance, we were led to make this investigation.Pure dilead arsenate, in the form of a fine amorphous powder, was prepared by adding to a solution of lead nitrate a solution of monopotassium arsenate in excess. The precipitate was separated by filtration and thoroughly washed.
oil-pyrethrum sprays for household use are ordinarily perfumed to cover the objectionable mineral oil odor. The perfumes used usually contain esters or other compounds which interfere with the determination of the active principles, pyrethrin I and pyrethrin II, by methods based on the titration of their mono-and dicarboxylic acids.
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