Bottles containing Hargreaves' salt and Hargreaves' salt cake

Bottles containing:- (a) Hargreaves' salt (b) Hargreaves' salt cake

These specimens show the type of material obtained in the ‘Hargreaves’ modification of the first stage of the process (specimens of which are 1876-269), by which salt cake is made without the use of sulphuric acid by the direct action of sulphur dioxide, air and steam on salt which has been previously formed into hard flat pieces. This process was first patented in 1870.