Iodoform, Chi
IODOFORM, CHI 3 , a valuable antiseptic discovered by G. S. Serullas in 1822; in 1834 J. B. Dumas showed that 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 CHa-CO-C . Its formation from alcohol may be represented thus: C2H 6 OH+ 4l 2 -r-6KHO = CHl 3 -r-KHC0 2 +5KI+5H 2 O. It crystallizes in yellow hexagonal plates, melting at 119-120 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, CHjIj.
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. Elbs 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 70 C., and a current density of one ampere per square decimetre is used. At the end of three hours a yield of 70 % of the theoretical quantity is obtained.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)
