Chemicals

The chemical industry has existed as long as there have been dyestuffs, cleaning agents, and medicines. Improvements in bleaching and dyeing made an important contribution to the English Industrial Revolution. Yet the chemistry of that era must look primitive to modern eyes. Experimental method was employed in laboratories, but, “The old industries were arts, conducted by skill of eye and hand, acquired by long practice of the craft; for this skill there was no substitute. The new industry has steadily discarded judgement and skill in favor of analytic control, calculation of the optimum conditions, and the check of experiment” (Taylor, 1957:12). The same chemical of different degrees of purity was often called by different names, and different chemicals known by the same name. The eighteenth century did see the scientific explanation of combustion, and elucidation of the relationship between salts, bases, and acids. The nineteenth century, though, would see much greater advance in chemical theory. In the first decade, Dalton applied atomic theory to chemistry. He assumed that all compounds combined elements in a simple numerical proportion. Compounds were thus limited in number, and of fixed composition. If there were different compounds of the same elements the elements must occur in numerical proportion: there was twice the oxygen/carbon ratio in carbonic acid as in carbonic oxide. Though there was no way of measuring these proportions at the time, chemical equations were of great use in understanding chemical reactions. By the middle of the century most of the industrial processes in use could be given an explanation in chemical terms; nonessential ingredients were identified, and the best temperature and volume for a reaction ascertained. About 1860, Canizarro in Italy extended Avogadro’s work to develop a theory for the establishment of atomic weights. Formulae of all substances which could be turned to vapor, including most carbon compounds, were thus ascertained. In 1882, Raoult developed a method to establish the formulae of all solubles (only in the 1920s, using X-rays, could the molecular weights of silicates be discovered). Also about 1860, valency theory was developed; this showed that 156atoms of particular elements always combine with a certain number of other atoms. This greatly facilitated the establishment of formulae for compounds.