Abstract: Compounds of the formula I ##STR1## in which R denotes alkyl, R.sub.1 denotes alkyl, alkoxy, alkylmercapto, alkylamino or dialkylamino, R.sub.2 and R.sub.3 independently of one another denote H, alkyl, cycloalkyl, benzyl or furylmethyl, R.sub.4 denotes alkyl, alkoxymethyl, alkylmercaptomethyl or phenyl and X denotes oxygen or sulfur, have valuable insecticidal, acaricidal and nematocidal properties.

Abstract: Manufacture of 3-hydroxy-1,2,4-triazoles by cyclization of corresponding semicarbazides by formic acid in the presence of an inorganic acid or halide thereof.

Abstract: Compounds of the formula I ##STR1## in which R is hydrogen, (subst.) alkyl, cycloalkyl, benzyl, phenylethyl or (subst.) phenyl, R.sub.1, R.sub.2 and R.sub.3 are alkyl and X is oxygen or sulfur are effective insecticides and acaricides and especially suitable for combating plant lice.

Abstract: An improved process for the manufacture of 2-chloroethane-phosphonic acid in which 2-chloroethane-phosphonic acid bis(2-chloroethyl) ester is heated with 50 to 500% by weight of aqueous hydrochloric acid at temperatures above 100.degree. C. under pressure, the 1,2-dichloroethane formed during the reaction is continuously or discontinuously distilled off and the decrease in pressure is compensated by adding gaseous hydrogen chloride.

Abstract: Compounds of the formula ##STR1## in which R.sup.1 is halogen, alkyl, alkoxy, alkylthio, CF.sub.3, NO.sub.2, CN.sub.2, phenoxy, halophenoxy, phenylthio or halophenylthio, R.sup.2 is CN or COOR.sup.3, R.sup.3 is alkyl, alkoxyalkyl or cycloalkyl and n is 0 to 3 are effective insecticides and acaricides and especially ectoparasiticides.

Abstract: Compounds having the formula ##STR1## in which R is alkyl, haloalkyl, cycloalkyl, cycloalkenyl, phenyl, optionally substituted by chlorine, methyl or methoxy, moreover bicycloheptyl or bicycloheptenyl; R.sub.1 is alkyl, optionally substituted by halogen, nitro, cyano or a radical having the formula ##STR2## ALKENYL, OPTIONALLY SUBSTITUTED BY HALOGEN; ALKINYL, ALKOXYALKYL, ALKYLMERCAPTO-ALKYL, CYCLOALKYL, PHENYL, HALOPHENYL, TRIFLUOROMETHYLPHENYL, BENZYL OR A RADICAL HAVING THE FORMULA ##STR3## R.sub.2 is alkyl, alkoxyalkyl, phenyl or halophenyl, R.sub.3 is methyl or ethyl, and X and Y are oxygen or sulfur are valuable pesticides.

Abstract: An improved process for the manufacture of 2-chloroethane phosphonic acid in which 2-chloroethane phosphonic acid bis(2-chloroethyl)-ester is heated with excess hydrogen chloride in the presence of 0.1 to 31% by weight of water at temperatures above 100.degree. C under pressure, the 1,2-dichloroethane formed during the reaction is continuously or discontinuously distilled off and the decrease in pressure is compensated by adding gaseous hydrogen chloride.

Abstract: Mono- and dithiophosphonic acid esters of the formula ##STR1## in which R is optionally substituted alkyl, cycloalkyl, cycloalkenyl, or optionally substituted phenyl, R' is optionally substituted alkyl, alkenyl, or cycloalkyl, R" and R'" which are identical or different, are hydrogen, halogen, methyl, methoxy, nitro or trifluoromethyl, and X is oxygen or sulfur, are useful insecticides and acaricides.

Abstract: Process for preparing phosphonic acid dihalides of the formula ##EQU1## wherein R is alkyl of 1 to 18 carbon atoms, cycloalkyl of 4 to 8 carbon atoms, alkenyl of 2 to 18 carbon atoms, phenyl, phenalkyl or alkyl-phenyl of 7 to 8 carbon atoms, phenyl, phenalkyl or alkyl-phenyl of 7 to 8 carbon atoms, all radicals R optionally being substituted by chlorine, bromine, cyano or lower acyloxy, and wherein X is halogen such as 2-chloroethane phosphonic acid dichloride, by reacting phosphonic or thio-phosphonic acids of the formula ##EQU2## wherein Y is oxygen or sulfur, their salts or functional derivatives, with acid halides of the formula(CO).sub.n X.sub.2 (III)wherein X is chlorine or bromine and n is 1 or 2, in the presence of 0.2 - 5% or in the presence of 0.01 to 0.2% by weight of1.