Some nitro and nitroso compounds have been determined by reduction with a known and excess amount of titanium(III) chloride solution and subsequent thermometric titration of the excess of the titanium(III) with an iron(III) solution.The accuracy is ±1 per cent. for 0·4 mequiv of sample and the time taken for a single titration is less than 2 minutes. The over-all time taken for a single determination is about 20 minutes.