Process for mfg. N-phosphonomethylglycine

A process whereby N-phosphonomethylglycine (glyphosate) or its salts is manufactured by: 1) forming N-phosphonomethylglycinonitrile by reacting aminomethylphosphonic acid, an alkali metal cyanide and formaldehyde in aqueous solution at a pH in the range from 10 to 13 (and preferably from 11 to 11.5) whilst adding mineral acid at a rate sufficient to maintain the pH within the desired range, and thereafter 2) hydrolysing the N-phosphonomethylglycinonitrile product of Stage (1) to form a salt of N-phosphonomethylglycine and optionally 3) neutralising the salt of N-phosphonomethylglycine to form N-phosphonomethylglycine