An Introduction to the Practice of Commercial Organic Analysis; Being a Treatise on the Properties, Proximate Analytical Examination, and Modes of Assaying the Various Organic Chemicals and Preparations Employed in the Arts, Manufactures, Medicine (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1879-01-01 Excerpt: ...and, lastly, distilling it over freshly burnt lime. The most delicate test for the presence of alcohol in chloroform is that of A. Lieben, as modified by Hager. For the details of the mode of applying it, see page 80. It depends on the fact that alcohol under the influence of iodine and an alkali yields iodoform, the properties of which are described below. Bromoform, CHBr3, closely resembles chloroform, but boils at 150-152C. Its density is 29 at 12C., or, according to E. Schmidt, 2-775 at 14-5 C. It solidifies at-9 C. Caustic potash converts bromoform into chloride and formate of potassium. By the action of alcoholic potash gas is evolved, consisting of one volume of carbon monoxide and three of ethylene; thus--CHBr3+3KC2H60=3KBr+2HaO + CO + 3C2H4. Bromoform is not unfrequently present in commercial bromine, even to the extent of 10 per cent. It may be detected by fractional distillation of the bromine on the water-bath, or by treating the sample with excess of solution of potassium iodide, and then adding sufficient sodium thiosulphate (hyposulphite) to take up the iodine set free. The characteristic odour of bromoform then becomes apparent. Iodoform, CHI3, is produced in Lieben's test for alcohol (page 80). It is a yellow, shining, crystalline solid, having an odour resembling saffron or a solution of iodine in chloroform. It volatilises at ordinary temperatures. Iodoform is almost insoluble in water (1 part in 13000) or glycerin, but is more soluble in alcohol (1 part in 80), and very soluble in ether and chloroform. Iu its chemical reactions it closely resembles chloroform. Its microscopic appearance is very characteristic, its usual forms being hexagonal plates, stars, and rosettes. When heated gently, iodoform volatilises without change, but a s.