dimethyl dithiophosphoric acid by the alkali treatment and, therefore, does not interfere.Cuprous ion interferes by forming with the dithiophosphate a colorless complex that is more stable than the cupric complex. Readily oxidizable materialse.g., mercaptans(thiols)-if not removed prior to addition of the copper reagent, will reduce the cupric ion and thus give low results. In the procedure described, mercaptans and other acidic impurities are removed by carbon tetrachloride extractions made on acidified aqueous solutionjust before addition of copper reagent.Small amounts of the following metallic ions do not interfere: iron(II), iron (III), zinc, nickel(II), cadmium, aluminum, tin (II), and lead. Wettable sulfur, fermate, parzate. cuprocide, aram-ite, toxaphene, parathion, ovotran, DDT, and methoxychlor do not interfere. Plant materials which have been analyzed by the method described include alfalfa, apples, barley, beets, broccoli, cauliflower, cottonseed, cranberries, cucumbers, eggplant, grapes, green beans (foliage and pods), kale, lettuce, lima beans (fresh and canned), mustard (fresh and canned greens), onions, peaches (canned), peas (canned), peppers, potatoes, spinach, strawberries, string beans (fresh and canned), Swiss chard, tobacco, tomatoes, and tomato juice (canned).Ginsburg, Filmer, and Reed (7) have applied the method to the analysis of corn, lima beans, lettuce, and onions; Kolbezen (2) to analysis of dates, walnut meats, pears, oranges, lemons, milk, avocados, and cantaloupe; and Westlake and Butler (3) to analysis of apples. pears, peaches, spinach, snap beans, cucumbers, broccoli, potatoes, strawberries, and peas.

A glc electron-capture method has been developed to measure nanogram amounts of Landrin insecticide and related carbamates after their reaction with trifluoroacetic anhydride. Concentrations of Landrin as low as 0.02 ppm in corn can be measured by this simple procedure. The trifluoroacetylated carbamates can be separated from one another on a 6-ft column packed with Gas Chrom Q coated with

nolic hydroxy group appears to be a factor influencing the toxicity. In this series of compounds, only those having the properties of aromatic phenols were satisfactory fungicides. This is in agreement with Sexton (20), who attributed the activity of oxine to its phenolic nature.The hydroxyl group in the 8-position on quinoline is an important toxiphore. Only those chelating agents which readily form stable lipophilic complexes with copper are strongly toxic. This finding is in agreement with Albert and associates (2, 3) and Block (6,7), who suggest that the 2 to 1 chelate is necessary for penetration, and that the site of action is inside the cell. Zentmeyer ( 22), assuming that 8-quinolinol precipitated trace metals from the medium, found that the toxicity could be reversed by adding excess metal ions. If the mechanism were simply one of precipitation, any strong chelating agent would be toxic. Zentmeyer did find that ammonium nitrosophenylhydroxylamine (cupferron) had considerable fungistatic value. Quinaldic acid

Techniques are described for the selective determination of two phosphate insecticides: 3-hydroxy-N,N-dimethyl-c/s-crotonamide dimethyl phosphate (Bidrin) and its N-monomethyl analog (Azodrin). The analysis is carried out in two steps: a separation procedure in which the pesticide is selectively extracted into aqueous solution and separated from interferences and other organophosphates by differential liquid-liquid partition, and an analytical procedure involving cholinesterase inhibition measurements. After differential extraction and cleanup, Bidrin and Azodrin are separated on a liquid-liquid chromatographic column with water as the stationary phase. This system has advantages of simplicity, sensitivity, and a high degree of specificity. Recovery experiments and specificity tests on 41 commercial insecticides are presented. Interference values from 37 of the insecticides tested were less than 1 % in the case of Bidrin, and in the case of Azodrin, only one insecticide, Dipterex, interfered to more than 2%. Auxiliary procedures are given for removing those insecticides which did interfere. The sensitivity of the method is 0.1 0 p.p.m. wo vinyl phosphates which have recently been found very effective for agricultural use are 3-hydroxy-A',Ardimethyl-cTr-crotonamide dimethyl phosphate (Bidrin insecticide

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