ABSTRACT
Although many nineteenth-century trades had a wide diversity of final products, most used a limited range of materials and turned out either a finished or an intermediate product which gave them a common basis for measuring output and growth, such as lengths of cotton thread or cloth, displacement of shipping launched or tonnage of puddled bar or ingot steel. In chemicals, on the other hand, materials, processes and intermediate products, as well as final products, were all so diverse that the only possible overall measures of change were value of output or size of workforce. Then as now the chemical industry was a congeries of trades rather than a trade (Hardie and Pratt, 1966). Technically their only common feature was that they employed processes of chemical change to convert raw materials into consumable form. The metal industries in this sense were the biggest chemical trades, but, both because of the type of product and still more the size of the industry, they are conventionally excluded.
