A process for the preparation of cationic hydrazone

Prepn. of cationic dyes of formula (I) comprises reacting azo base (II) with dialkyl sulphate (III) in presence of water and of Na2SO4 or MgSO4. The reaction is opt. followed by exchanging the alkyl sulphate for some other anion. R1 = H, 1-4C alkyl or alkoxy, NO2 or halo; R2 = H, 1-4C alkyl or alkoxy, halo or phenylazo; R3 = 1-3C alkyl; A = anion. The wt' ratio (II):sulphate is 1:0.5-4 and the mole ratio (II):(III) is 1:1.5-5.