Chlorhidroquinone is considerably more active than hydroquinone. In pure state, it is white or cream color, but the commercial product is usually tan or pinkish-brown. Chlorhidroquinone can be substituted for hydroquinone in the common MQ formulas, and for paper development there is considerable advantage in this, since there is much less tendency to aerial fog. There is no advantage, however, in negative developers, since film emulsions resists this type of fog.
Edmund W. Lowe, “What You Want to Know About Developers Fine Grain and Otherwise”, p. 55.