The first efforts were directed towards the process by which, as we eventually ascertained, the Germans produced the whole of their mustard gas. The actual chemical laboratory details of the process presented no serious obstacle, but difficulties multiplied as soon as we attempted large scale work. We wanted ethylene-monochlor-hydrin. Some work had been done on this during the war for the National Health Insurance Commissioners in connection with the production of novocain. Half scale work had occurred at the works of a Midland chemical firm, and experience so gained was freely offered and used in a scheme for the large scale production of mustard gas by the co-operation of a number of big chemical manufacturers. Pressing requests for the material were continually coming from G.H.Q., the programmes outlined being more and more ambitious. We had to reproduce the result of years of German effort spent in developing their monochlor-hydrin process for indigo. As a consequence, large sums of money were expended on the process, although it never eventually operated. Its difficulties, and other reasons, led us to research on other and more direct methods which the French were also investigating. The successful outcome of this early research was due, in particular, to Sir William Pope and those associated with him in the work. The process was so promising that the long and cumbersome chlor-hydrin method was abandoned. As a result our five or six months' work on the German method meant so much time lost. The new direct, sulphur monochloride method was taken up actively and several private firms attempted to develop the small scale manufacture. The work was dangerous. Lack of that highly developed organic chemical technique, which was practically a German monopoly, rendered the task much more dangerous than it would have been if undertaken by one of the I.G. factories.