Chemistry owes much to the catalytic forces which effect otherwise difficulty accomplished reactions. To catalysis Organic Chemistry owes the Grignard reagents, which have been employed not only for a multitude of simpler syntheses but also for the more complex syntheses of carbohydrates (Paal. Ber, 1905, 38 1656; 1906,39,1301,2823, 2827) Frankland and Twiss J.C.S. 1905, 87, 864), of terpenss (Perkin J.C.S. 1907, 91, 480, Hesse Ber. 1909, 42, 1127, Mills and Bain J.C.S. 1910, 97, 1866) and of organo-silicon compounds (Kipping J.C.S. 1901 to 1909). Pope and Peachy effected resolutions of tin compounds with its aid. Chlorination is effected catalytically by suitable carriers. The Friedel and Crafte reaction is effected also by suitable halides. Numerous condensations such as the Benzoin condensation, the Aldol condensation, the Claisen condensation, and also esterification are catalytically effected. Equilibria between dynamic isomerides, in racemisation, and in mutarotation, are promoted by catalysis. Technical chemistry has, through catalysis, reversed the economic standing of nations. Cases in point are the synthesis of indigo, a stage in which is the catalytic oxidation of Napthalene by Sulphuric acid and Mercury, and the manufacture of sulphuric acids, of Ammonia and of Nitrates. The manufacture of synthetic petrols, power alcohols, and the new utilisations of coal depend entirely upon catalysts for their successful functioning. Analytical chemistry employs catalysts in processes of gas absorption such as addition of Uranyl Sulphate to Sulphuric Acid in the absorption of Ethylene (Lebeau and Damiens Compt. Rand. 1913, 156, 557) or of Corrosive Sublimate to alhaline Pyrogallol to accelerate the absorption of Oxygen. (Stassana, Compt. Rend. Soc. Biol. 1905, 58, 96). Also in Oxidation, such as the permanganate titration of iron in the presence of Hydrochloric and of Manganese Salts (Kessler. Pogg. Am. 1863, 118, 48; 119, 225), or the ability of Ferrous Sulphate to promote interaction between Potassium Persilphate and Potassium Iodide (Price Z Phys. Chem. 1898, 27, 474); and Reduction as in the employment of a Zinc-Copper Couple for the reduction of Chlorates to Chlorates (Thorpe and Eccles J.C.S. 1873, 26, 541; Bothamley and Thompson Ibid 1888, 53, 164). Catalysts are also employed in Organic analysis, as for example the use of colloidal platinum metals to convert Halogen compounds into Hydrogenated products and Halogen acid in the presence of Hydrogen (Borshe and Heimburger, Ber. 1915, 48, 452, 850). In Inorganic Chemistry a large number of reactions are catalytically accelerated. One of the best known is the decomposition of Potassium Chlorate in the Presence of Manganese Dioxide. Numerous catalyses are cited in the work of Dhar. (Ann. Chim. 11, 130-223, 1919). Hydrogen peroxide, another example of classical importance in chemical kinetics is decomposed by numerous agents, such as glass wool, salts of heavy metals, colloidal platinum. In Electrochemistry one may cite such examples as the addition of Fluorides in the preparation of Persulphates or percarbonates, (Muller and Friedberger, Z. Elektrochem., 1902, 8, 230), or the use of Lead Peroxide anodes in the oxidation of Chromates to Dichromates (Z. Elektrochem, 1905, 11, 863). Para-nitrotoluene with platinum anodes yields p-nitro-benzoic acid almost quantitatively. An enormous number of reactions is accelerated by radiant energy, according to photo chemical laws. A typical example is the union of Hydrogen and Chlorine, whose mechanism has occupied the attention of numerous workers. The photocatalytic combination of carbon-monoxide and Chlorine, of Sulphur Dioxide and Chlorine, of saturated, unsaturated, and aromatic hydro-carbons, and of acids (much as Acetic acid) and Chlorine furnish still further examples. Such reactions are further sensitive to the presence of ordinary material catalysts or anti-catalysts (See Griffiths and McKeowan, (“Photochemistry” p. 626.)