The most convenient hydrogen chloride generator is that described by Sweeney.[1] Concentrated hydrochloric acid is introduced into concentrated sulfuric acid, by means of a dropping funnel and a _capillary tube leading to the bottom of the sulfuric acid container_. It is convenient to use a 3-l. bottle for this container and a 1-l. funnel to contain the hydrochloric acid. The gas is dried by passing through a wash-bottle containing concentrated sulfuric acid. An empty catch-flask should be connected between the generator and the absorption flask in case any glycerol tends to suck back at the start of the reaction. About 6 kg. of concentrated hydrochloric acid and 10 kg. of concentrated sulfuric acid are required in one run. The generating flask will have to be recharged every six hours; it should be half filled with sulfuric acid. Aside from this, the apparatus needs no attention. The oil bath can be conveniently heated on an electric hot plate. The dichlorohydrin boiling over a 7'0 range is sufficiently pure for most purposes. It contains very little, if any, isomeric dichlorohydrin, since on oxidation it gives dichloroacetone in good yields. 3. Other Methods of Preparation The following methods of preparing dichlorohydrin are described in the literature: the action of gaseous hydrogen chloride on glycerol;[1b] the action of gaseous hydrogen chloride on glycerol mixed with an equal volume of acetic acid;[2] the action of hydrogen chloride gas on glycerol containing 1-2 per cent of some organic acid, as acetic, as a catalyst;[3] the action of aqueous solution of hydrochloric acid on glycerol containing acetic acid as a catalyst;[4] the action of sulfur monochloride on glycerol.[5] The previous work, described in the literature, indicated that the best yields were obtained by the treatment of glycerol containing 1-2 per cent of acetic acid as a catalyst by gaseous hydrogen chloride. Therefore this method was employed. [1a] J. Am. Chem. Soc. 39, 2187 (1917) [1b] Ann. 88, 311 (1853); Ann. chim. phys. (3) 41, 297 (1854); (6), 22, 437 (1891); Bull. soc. chim. (2), 48, 237 (1887); Z. physik. Chem. 92, 717 (1918); 93, 59 (1919); 94, 691 (1920); D. R P. 263,106; 272,337; Frdl. 11, 33 (1912). [2] Ann. Spl. 1, 2I8 (1861); Ann. chim. phys. (3) 60, 18 (1860). [3] D. R. P. 197,308; Frdl. 9, 33 (1908). [4] D. R. P. 197,309; Frdl. 9, 33 (1903). [5] Ann. 122, 73 (1862); 168, 43 (1873); Ber. 5, 354 (1872); Ann. chim. phys. (6) 22, 437 (1891). IX GLYCEROL a-MONOCHLOROHYDRIN C3H5(OH)3 + HCl--> CH2ClCHOHCH2OH + H2O Prepared by J. B. CONANT and O. R. QUAYLE. Checked by O. KAMM and A. O. MATTHEWS. 1. Procedure