Abstract: A method and catalyst for the determination of nitrate in water which has been obtained by reduction of a solution of a salt of a transition metal or group VIII of the periodic system and a transition metal salt of the copper group in the presence of an acid. The nitrate determination is effected by determining the nitrate extinction of a sample of water as compared with a blank sample in the UV region at 210 nm, a part of the sample of water whose nitrate has been reduced in the presence of hydrogen with the use of the catalyst of the invention being employed as blank sample.