Twelve ureas and thioureas with 1,3-diphenyl-and l-phenyl-3-(2-pyridyl) were tested as potential herbicides in a simple screen against two species of algae Chlorella .fusca and Anabaena variabilis. Several were shown to inhibit growth at 100 mg litre-1 but only 1 -[2,4-bis(azidosulphonyl)phenyl]-3-(2-pyridy~)urea and 1,3-bis(4-isopropyl-idenehydrazinosu1phonylphenyl)thiourea showed any activity at 1 mg litre-1. This compares with the wellestablished urea herbicide diuron which, in identical tests, gives similar inhibition of growth at concentrations as low as 0.01 mg litre-1.

Dyes containing sulphonylazido, carbonylazido, arylazido and azidoacetamido groups have been synthesized. These dyes react chemically with synthetic‐polymer fibres, such as polyester, nylon and cellulose acetate. Their dyeing and fastness properties are discussed.

Die Acetylierung von Phenylharnstoff (I) mit Acetanhydrid und konzentrierter Schwefelsäure liefert das N‐Acetylderivat (III), während mit Acetanhydrid und Pyridin keine Acetylierung erreicht werden kann.