CHI3

IODOFORM  , a valuable antiseptic discovered by G . S . Serullas in 1822; in 1834 J . B . Dumas showed than it contained hydrogen . It is formed by the action of iodine and aqueous potash on ethyl alcohol, acetone, acetaldehyde and from most compounds containing the grouping CH3•CO•C– . Its formation from alcohol may be represented thus: C2H5OH+ 412+6KHO= CHI3+KHCO2+5KI+5H20 . It crystallizes in yellow hexagonal plates, melting at 119-1200 C., and is readily soluble in alcohol and ether, but is insoluble in water . It has a characteristic odour and is volatile in steam . On reduction with hydriodic acid, it yields methylene iodide, CH2I2 . More recently, iodoform has been prepared by the electrolysis of a solution of potassium iodide in the presence of alcohol or acetone, the electrolytic cell being fitted with a diaphragm, in order to prevent the hydrogen which is formed at the same time from reducing the iodoform, or from combining with the iodine to form hydriodic acid . K .

Ellis uses a solution of potassium iodide and sodium carbonate in water, which with the necessary alcohol is contained in a porous cell fitted with a lead anode, whilst the cathode compartment contains a solution of caustic soda and a nickel electrode . The electrolysis is carried out at a temperature of 7o° C., and a current density of one ampere per square decimetre is used . At the end of three hours a yield of 7o 04, of the theoretical quantity is obtained .