Paper, 'Experiments on vapour-density' by Edgar Philip Perman Perman writes: 'The main purpose of my work on this subject was to discover if bromine had any tendency to dissociate at low pressures, i.e., down to about 15 mm. of mercury, and at moderate tem peratures. The subject was suggested by Professor [William] Ramsay, to whom I am greatly indebted for constant advice and assistance in carrying out the work.' Annotations in pencil and ink. Includes three pages of diagrams of experimental apparatus. Subject: Chemistry Received 17 April 1890. Read 8 May 1890. Communicated by Ramsay. A version of this paper was published in volume 48 of the Proceedings of the Royal Society as 'Experiments on vapour-density'. 1890