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Abstract

Trivalent chromium is electrodeposited from an aqueous bath in which are dissolved very small proportions of compounds of classes (I) compounds containing ##STR1## group, preferably a thiocyanate or a compound of formula X--CSNR where X is R, S or, NR.sub.2 or is --CSNR.sub.2 joined by --S-- or --S--S-- and R is H, alkyl, alkenyl, alkynyl or aromatic: (II) compounds of formula (X)--SO.sub.2 --(Y) in which X is (a) a saturated or unsaturated two or three carbon atom alpiphatic group terminating in a mercapto group or (b) the disulphide corresponding thereto, of formula Y--(SO.sub.2)--X--S--S--X(SO.sub.2)--Y or (c) single unsubstituted benzene ring; and Y is --ONa, --OH, --NH.sub.2 or when X is a single unsubstituted benzene ring, a direct --NH-- linkage or indirect --NH--CO-linkage to the ortho position thereof, (III) compounds of formula HOOC --(CH.sub.2).sub.n --S.sub.m (CH.sub.2)COOH where n or m is 1 or 2; (IV) o-mercaptobenzoic acid and (V) sodium salts of sulphur, selenium and tellurium.

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First Claim