CHEMICAL ARTICLES. The main article CHEMISTRY includes a general survey of the History of Chemistry, and also deals comprehensively with the various branches of this science; viz., Inorganic, Organic, Physical and Analytical Chemistry. These and their practical applications are treated in fuller detail in the chemistry articles appearing in this encyclopædia.
There are articles elucidating fundamental ideas and definitions, and explaining chemical changes; e.g., ACID; ATOMIC WEIGHTS; CHEMICAL ACTION ; COMBUSTION ; ELEMENTS, CHEMICAL ; MOLE CULE, CHEMICAL; OXIDATION AND REDUCTION. ATOMIC WEIGHTS contains a list of the elements ; these are described individually, with their chief compounds, in separate articles. There are also separate articles on the more important compounds; e.g., AMMONIA. The compounds of carbon, apart from the simple ones treated under the separate headings (such as CARBONATES; CAR BONYLS, METALLIC; etc.), are dealt with in the organic chemistry articles.
Organic Chemistry, a main sub-section of CHEMISTRY, includes a historical introduction followed by a general survey of the sub ject under the sub-heads Aliphatic, Homocyclic and Heterocyclic Divisions. CHEMISTRY also includes an account of Ultimate Or ganic Analysis. There are, besides, articles explaining the struc ture and synthesis of carbon compounds; e.g., ISOMERISM and STEREOCHEMISTRY; and processes and reagents are described under HYDROGENATION, GRIGNARD REAGENTS, etc. The various types and classes of compounds are dealt with in Azo COMPOUNDS, ALKA LOIDS, ALCOHOLS, ESTERS, KETONES, CAMPHORS, PURINES, etc.; separate articles are devoted to the more important sub-groups and members of these classes; e.g., BUTYL ALCOHOLS, ALCOHOL (ethyl alcohol), BENZENE, CHLOROFORM, PYRIDINE, etc., many being of industrial and medical importance. The chief substances present in living matter are treated under ALBUMIN, CARBOHY DRATES, CHLOROPHYLL, PROTEINS, RESINS (NATURAL AND SYN THETIC), etc.; and several organic acids have separate headings; e.g., ACETIC, CARBOLIC, OXALIC and URIC ACIDS. Dyes and pig ments are dealt with in DYES, NATURAL and SYNTHETIC, and under various headings such as ALIZARIN, ANTHOCYANINS AND ANTHOX ANTHINS, GLUCOSIDES (NATURAL), INDIGO, OCHRES, etc.
The physical chemistry articles include ADSORPTION, ASSOCIA TION, CATALYSIS, HYDROGEN ION CONCENTRATION, PHOTOCHEMIS TRY, VALENCY, THERMOCHEMISTRY, etc. The industrial processes are treated in CHEMICAL ENGINEERING, COAL TAR, DISTILLATION, EXPLOSIVES, SUGAR, etc., and under the separate headings of the various important elements and compounds. There is a large col lection of diagrams of apparatus used in a chemical laboratory under CHEMICAL APPARATUS, and the methods of chemical analy sis are described in CHEMISTRY: Analytical, which includes In organic (qualitative and quantitative), Ultimate Organic and Gas Analysis, and in BLOWPIPE and INDICATORS. There are also short articles interpreting old-fashioned names and dealing with various theories of the alchemists, e.g., ALCHEMY; AQUA REGIA, BRIM STONE, ELIXIR, HARTSHORN, SPIRITS OF; and VITRIOL.