— 141 — 



cock 1 ), on the formation of formic acid by the atmospheric oxidation of 

 turpentine. He pointed out that, in spite of the large number of references to 

 the subject, dating from earlier up to recent times, it could not be held that 

 the production of the acid in the manner described had been positively 

 proved, since no analytical figures had been given. Kingzett had observed 

 a considerable formation of a dirty reddish-brown crystalline substance 

 in a galvanized iron tank which was in use for the storage of air-oxidised 

 Russian turpentine, and had examined these crystals. By frequent suc- 

 cessive recrystallisation from hot water he succeeded in removing the 

 colouring-matter due to the admixture of insoluble iron-compounds and 

 in obtaining the body in the form of white crystals. When analysed, 

 (by the calomel method and by direct estimation of the formic acid after 

 isolating with dilute sulphuric acid and distilling with steam), these 

 crystals were found to consist of pure zinc formate (HCOO) 2 Zn + 2H 2 0. 

 The formic acid is certainly produced by oxidation of the turpentine or of 

 a primary oxidation-product by the agency of atmospheric oxygen. Further 

 experiments showed that this oxidation is only set up in the presence of 

 water or moisture, and that in addition to formic acid, acetic acid is also 

 produced, because the aqueous liquid contained more acid than was 

 accounted for by the calomel-precipitate. For instance, in 100 cc. water 

 which had separated out at the bottom of an oxidised oil, 0,0527 g. formic 

 acid and 0,2436 g. acetic acid was found, but a portion of these acids 

 may have been present in the original oil, as was found to be the case 

 with aqueous washings of Russian and Swedish oils. Samples of Russian, 

 Swedish, and American oils were placed in dry test-tubes, zinc foil being 

 suspended over the samples and the tubes covered with watch glasses. 

 After being left standing for several weeks it was found that no action 

 had taken place upon the metal. But when the test-tubes were placed 

 together in a beaker containing water, the foil was rapidly covered with 

 a white incrustation of zinc formate, even when the tubes were covered 

 with watch glasses. 



In the discussion following, Coste mentioned that he had obtained similar 

 results, and asked whether a reliable varnish or other covering was known 

 for protecting the turpentine-tanks. Kingzett replied in the negative, but 

 added that he did not think such a covering was required, because the metal 

 was only attacked when the oil was brought into contact with water or 

 moisture, that is to say at the seams on the upper surface and at the 

 bottom seam between the oil and any water which might have separated. 



For the reduction of turpentine oil, see pinene, p. 174. 



Vetiver Oil. During the period under review there was no lack of 

 suitable material for the preparation of our own distillate, which is 



*) Journ. Soc. chem. Industry 29 (1910), 791. 



