This section is from the book "Alcohol, Its Production, Properties, Chemistry, And Industrial Applications", by Charles Simmonds. Also available from Amazon: Alcohol: Its Production, Properties, Chemistry, And Industrial Applications.
When methyl alcohol vapour is passed over reduced copper at a temperature of about 200-240°, it is decomposed into formaldehyde and hydrogen (Sabatier and Senderens). At higher temperatures, the formaldehyde is partly destroyed, carbon monoxide being produced. Thus, according to Mannich and Geilmann,1 at 240-260° the evolved gas contains 10 to 12 per cent. of carbon monoxide, corresponding with the decomposition of about one-seventh of the primarily formed formaldehyde. A large proportion of the latter is polymerised to methyl formate.
With reduced nickel as catalyst in the place of copper, Sabatier and Senderens found that the action is more violent and takes place at a lower temperature, but partial decomposition of the aldehyde cannot be avoided. Reduced cobalt acts similarly to nickel. Platinum sponge also effects the decomposition of the alcohol, but at a higher temperature.2
The catalytic decomposition of methyl alcohol is of considerable technical importance in the production of formaldehyde. Reduced copper, platinised asbestos, and silvered gauze or pumice are commonly used as the catalysts. Formaldehyde itself is largely used in the dyeing industry, in making certain medicinal products (hexamine), and in the manufacture of synthetic resins (bakelite).
If methyl alcohol is heated in absence of air, in a vessel provided with a reflux condenser, by means of a platinum or nickel wire electrically heated to about 700°, hydrogen and carbon monoxide with traces of dioxide are given off, and formaldehyde is found in the reaction vessel. If ammonia is dissolved in the methyl alcohol, the formaldehyde is converted into hexamethylenetetramine.3 A mixture of methyl alcohol vapour and air yields formaldehyde when exposed to sunlight, though not when kept in the dark at the ordinary temperature, and only traces at 100°.4
Applications, - Methyl alcohol finds important applications in the manufacture of medicinal and photographic chemicals and of dyestuffs. It is employed both as a solvent - as, for example, in the preparation of "Salvarsan" - and as a means of introducing methyl groups into a compound. For this latter purpose, it is usually employed in the form of a salt or ester, e.g., methyl sulphate, chloride, iodide, or picrate. Methyl anilines are largely used in the preparation of certain dyestuffs. Methyl salicylate, or synthetic oil of wintergreen, is of some importance in medicine, and is also employed as a constituent of flavourings. Various methyl esters are used in perfumery, as, for instance, methyl benzoate (Niobe essence), methyl anthranilate, methyl cinnamate, and methyl beta-naphtholate (nerolin).
1 Ber., 1916, 49, 585 2 Compt. rend., 1903, 136, 921.
3 Lob, Zeitsch. Elektrochem., 1912, 18, 847.
4 H. D. Gibbs, Phil. J. Sci., 1912, 7, 57.
In its less pure forms as wood spirit or wood naphtha, methyl alcohol is largely used as a solvent for resins in the varnish industry, and it finds an important application in the denaturing of ethyl alcohol used in manufactures.