of sulfophosphoric acid and phosphorus oxychloride, as well as of copper hydride. But his original work was mainly in the domain of organic chemistry. Investigation of the cyanic ethers (1848) yielded a class of substances which opened out a new field in organic chemistry, for, by treating those ethers with caustic potash, he obtained methylamine, the simplest organic derivative of ammonia (1849), and later (1851) the compound ureas. In 1855, reviewing the various substances that had been obtained from glycerin, he reached the conclusion that glycerin is a body of alcoholic nature formed on the type of three molecules of water, as common alcohol is on that of one, and was thus led (1856) to the discovery of the glycols or diatomic alcohols, bodies similarly related to the double water type. This discovery he worked out very thoroughly in investigations of ethylene oxide and the polyethylene alcohols. The oxidation of the glycols led him to homologues of lactic acid, and a controversy about the constitution of the latter with Adolph Wilhelm Hermann Kolbe resulted in the discovery of many new facts and in a better understanding of the relations between the oxy- and the amido-acids. In 1855, he published work on what is now known as the Wurtz reaction. In 1867 Wurtz synthesized neurine by the action of trimethylamine on glycol-chlorhydrin. In 1872 he discovered the aldol reaction and characterized the product as showing the properties of both an alcohol and an aldehyde. Alexander Borodin discovered the reaction independently in the same year. The product was named an aldol, pointing out its double character. This led to a second confrontation with Kolbe. In addition to this list of some of the new substances he prepared, reference may be made to his work on abnormal vapor densities. While working on the olefins he noticed that a change takes place in the density of the vapor of amylene hydrochloride, hydrobromide, &c, as the temperature is increased, and in the gradual passage from a gas of approximately normal density to one of half-normal density he saw a powerful argument in favor of the view that abnormal vapor densities, such as are exhibited by sal-ammoniac or phosphorus pentachloride. are to be explained by dissociation. From 1865 onwards he treated this question in several papers, and in particular maintained the dissociation of vapor of chloral hydrate, in opposition to Etienne Henri Sainte-Claire Deville and Marcellin