CHEMICAL AND PHARMACEUTICAL PRODUCTS.

INTRODUCTION.

The results of the science directly illustrated by this Class will probably be more generally appreciated thanthe means by which such results are attained. But these are not to be sought among the chemical and phar-maceutical products, any more than are the beautiful mechanisms of other Classes to be found in association withthe raw mineral which supplied the material for their formation.

This Class is principally contained in the South Gallery, and is most conveniently reached by ascendingthe stair near the south entrance at the transept. The objects in the Class are immediately encountered ongaining the Gallery. The Class is divisible into the following heads :—A. Chemical substances used in manu-facture. 13. Rarer chemical substances for the scientific chemist; and C. Chemical substances used in medicine.

The objects in this Class do not admit of more than a general grouping, into the chemicals of the chemicalfactories, and the more delicate and refined compounds produced in the laboratory. The former of these, inclu-sive of large specimens of alum, protosulpliate of iron (copperas), and soda are interesting as representinga department of British commerce which has grown into importance within a very recent period. The manu-facture, especially of caustic and carbonate of soda on the great scale, has originated and developed itself in adegree almost unparalleled in the history of commerce within twenty or thirty years of the present time. Thefires of the kelp burners on the shores of the islands of Scotland are scarcely now extinct, when vast factories,employing large numbers of individuals appear to produce in enormous quantities the same alkali, which wasuntil recently scantily derived from the fused ashes of marine plants. The manufacture of this alkali, by aningenious decomposition of common salt by the simple aid of sulphuric acid, chalk, sawdust, and coal, is nowprosecuted to a vast extent for the supply of the industrial arts generally, the quantity used in medicine andpharmacy being comparatively insignificant. At some alkali works fifty and sixty tons and upiwards of commonsalt are decomposed every week, and converted into caustic or carbonate of soda. The alum factories arcnot less extensive. At those establishments crystallizations on a scale emulating those of nature are constantlyin progress. Some very large specimens of these crystals, and of those of other chemical compounds arepilaced in the Central Avenue, some of the masses being 8 feet in height. The manufacture of sulphuricacid, and of the compxmnds used by the dyer and calico-printer, also occupies a prominent feature of commercialenterprise. The prussiates of piotash forming large masses of yellow and red crystals, and. the green, but perish-able crystals of copiperas, are illustrations of substances largely used in the arts, and the colours and dyes pro-duced by their assistance, present themselves in every direction, when the classes relating to textile printedfabrics are examined.

The chemical works of this country arc principally situated at Liverpool, at Newcastle-upxm-Tyne, and atGlasgow . The area of ground occupied by some of them equals that covered by the Exhibition Building, and inthe various departments as many as five or six steam-engines are employed. The chimneys of these works arein one or two instances 500 feet in height, and the workmen employed form a little population resident in theimmediate vicinity of the works.

The application of scientific chemistry to the prarposcs of medicine is scarcely less recent than the commercialdevelopment of chemical manufacture. Medicinal substances appeared for a period to have been overlooked bythe chemist, and little attention was given to their preparation. This cannot now be said. The specimens ofvegeto-alkaloids, the minerals used in pharmacy and of their compounds—of beautiful crystalline forms,indicate the progress made in the application of philosophic chemistry to the production of pharmaceutical pre-parations. A variety of compounds obtained by delicate chemical reactions, and from substances requiringgreat carefulness in manipulation, are also included in this Class.

The whole Class, though not an extensive one, represents the growing attention of men of eminence tochemistry as a manufacture ; and of men ol science to the application of chemical philosophy to the processescarried on on the smaller scale in the laboratory. . The same facilities which exist in this country for the pro-secution of other depiartments of commercial and industrial enterprise have carried chemical manufactures totheir present important and commanding piosition. The direct dependence of many of the arts upion theexistence of and the accuracy of production in these chemical works cannot now be questioned.—11. E.