The synthesis of forty‐one phenazines, mono‐substituted with alkyl, alkoxy, alkylthio and alkylsulphonyl groups is described. Phytotoxicity was highest in the alkyl series and both 1‐ and 2‐methylphenazines are highly effective. herbicides. Although several n‐alkyl, branched alkyl and n‐alkoxyphenazines were highly fungicidal and acaricidal, only 2‐t‐octylphenazine combined high dual activity with negligible phytotoxicity.

A confirmatory method for the positive identification of toxaphene in small residues has not previously been reported. A sensitive method for the qualitative and quantitative determination of toxaphene in residues and in formulations is based on fusion with diphenylamine in the presence of zinc chloride. The greenish blue reaction product, dissolved in acetone or glacial acetic acid, has an absorbance maximum at 640 mp. Toxaphene in the range of 20 to 700 y can be readily determined b y spectrophotometric measurement. When combined with cleanup procedures, the method has been applied to extracts of crops and foods and to various formulations, including mixtures with sulfur or DDT.HE need for an accurate method for T the specific determination of micro quantities of toxaphene in food and forage crops and in milk and beef has become increasingly apparent with the more widespread use of this insecticide. Toxaphene is chlorinated camphene containing 67 to 69% chlorine. Microdetermination by a sensitive method for organic chlorine (5) has been widely used for determining toxaphene residues, but this method lacks specificity. Macrodetermination by an infrared method ( 4 ) is specific, but has not been employed as a residue method because of Ion sensitivity. A qualitative colorimetric test with pyridine and methanolic potassium hydroxide has been reported ( 3 ) .

Analysis for traces of residues from chlorinated pesticides by combustion methods offers many advantages over other decomposition methods which involve chemical reagents.

The synthesis and biological activity of twenty-six halophenazines is described. The Wohl-Aue reaction and the new method for cyclisation of 2-nitrodiphenylamines by oleum were found to be the most convenient methods of synthesis.Phytotoxicity of a characteristic type was higher in foliar spray than in pre-emergence tests. Chlorine substitution appeared to confer higher activity than other halogen substituents, and in the chlorophenazines activity decreased with increasing substitution. Both 1-and 2-chlorophenazine were highly effective herbicides.Acaricidal and fungicidal activity showed similar responses to structural changes, and optimum activity, together with a low level of phytotoxicity, was reached with 1,4-dichlorophenazine.

Residues of the acaricidal material 2,3-p-dioxanedithiol S,S-bis(0,0-diethyl phosphorodithioate) (Hercules AC-528) on navel oranges and lemons have been evaluated, using a semispecific colorimetric procedure. Half-life values for persisting residues of the acaricide on field-sprayed navel oranges and lemons were determined to be about 95 and 85 days, respectively. Less than 0.03 p.p.m. of this material was found in the edible portion of the fruit.