in 1848 he was engaged by the cavendish society to translate into english and enlarge leopold gmelin's classic "handbuch der chemie", a work which occupied much of his time till 1872, when the last of its eighteen volumes appeared. in 1863-67 he was co-author with thomas richardson of the last three volumes of the second edition of "chemical technology", written by friedrich ludwig knapp, edmund ronalds and richardson.  in 1858 he was engaged by messrs. longmans & co. to prepare a new edition of the "dictionary of chemistry and mineralogy" of andrew ure; but the book was obsolete, and he transformed it, with the help of a staff, into an encyclopædia of chemical science. the first edition of watts's "dictionary of chemistry", in five volumes, was completed in 1868; supplements were published in 1872, 1875, and 1879–81. a new edition, revised and entirely rewritten by m. m. pattison muir and henry forster morley, was published 1888–94, 4 vols.