In January 1783, Price returned to his laboratory in Guildford, ostensibly to start production of the miraculous powders. In fact, he set about the distillation of laurel water (which contained hydrogen cyanide, commonly known as prussic acid). He wrote his will at the same time, but it was another six months before he returned to London to invite members of the Royal Society to witness the experiment on 3 August in his laboratory in Guildford.

Despite the claimed successes of his initial demonstrations and the furor they had caused, only three members turned up in Guildford on the appointed day. Although clearly disappointed by the poor turnout, Price welcomed the three men and then, stepping to one side, ended his life by drinking the flask of laurel water he had prepared. The three men immediately noticed a change in his appearance, but before they could do anything, Price had died of cyanide poisoning.