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j - NOTES ON SCIENTIFIC RESEARCH. 103 
vanillin-ferrate, [Fe (Cs Hs(CHO)(OCHs) O)4] Na + 1/2H.O, forms an almost black powder, 
which under the microscope appears to be composed of tiny reddish violet needles. 
There are further described: potassium pentavanillin-ferrate, sodium tetraeugenol-ferrate, 
a compound of potassium tetraeugenol ferrate and eugenol and the potassium salt of 
tetraeugenolferric acid. 
The ferric acid of methyl salicylate had previously been prepared’). 
Several years ago, M. Otto and A. Verley’) found that isoeugenol can be converted 
into vanillin by oxidation with ozone. A German firm opposed at the time the grant 
of a patent for this process, alleging that it was impracticable. By order of the German 
Patent Office, O. N. Witt undertook the verification and, on account of his experiments, 
arrived at the conclusion that the French method did not lead to the indicated results. 
Nevertheless a French factory produced several kilos of vanillin daily by this process, | 
Later on it was compelled, it is true, to stop the manufacture, as the ozonation did 
not work properly and did not pay either. 
The investigations, continued through many years by C. Harries, have now led to 
a complete elucidation of the process chemically speaking, on which he reports together 
with R. Haarmann®). It has been found that the preparation of vanillin from isoeugenol 
affords a satisfactory yield only if ozone of low percentage is used. Witt*) employed 
from the very beginning a big apparatus for the production of concentrated ozone, as 
in the application for a patent much stress had been laid on the use of a highly 
concentrated ozone, which, according to the conception of those days, corresponded 
to air containing 3 p.c. ozone. As Harries remarks, in this way Witt could only arrive 
at resinous products when starting from zsoeugenol. Harries and Haarmann succeeded 
best with a 1 p.c. ozone. In this manner they treated not only ¢soeugenol, but also 
some other phenols and phenolethers. They prepared 1 p.c. ozone by conducting 
14 p.c. ozone first through 5 p.c. soda lye, then through concentrated sulphuric acid 
and finally through a tube 40 cm. long and containing phosphorus pentoxide, thus 
considerably reducing the contents of ozone. In hexane solution isoeugenol gave a 
rather unstable, normal ozonide. In another experiment, isoeugenol in glacial acetic 
acid was saturated with 1 p.c. ozone and the solution heated on a water-bath, when 
gases were evolved and acetaldehyde escaped. After the glacial acetic acid had been 
distilled off im vacuo, an oil remained, from which by repeated distillation 37,8 p.c. of 
the theoretically possible quantity of vanillin was obtained. 
Oxygen alone can likewise oxidize isoeugenol to vanillin. For this purpose dry 
oxygen was introduced into a solution of isoeugenol in glacial acetic acid, when at 
least 12 p.c. of vanillin formed. 
A much better yield of vanillin is obtained by reducing the ozonide. Isoeugenol 
in dry ethyl acetate was saturated with 1 p.c. ozone, the acetate distilled off in vacuo, 
the oily residue, isoeugenol ozonide, dissolved in ether and reduced by gradually 
adding zinc dust and glacial acetic acid under cooling. After the excess of zinc dust 
had been removed, the ethereal solution was shaken with precipitated calcium carbonate 
and water, the ether being then removed and evaporated. The residue yielded 71 p.c. 
of vanillin (m. p. 73°) on distillation in vacuo. The yield is not inconsiderably increased 
if the distillation is carried out under strongly reduced pressure at 0,3 to 0,5 mm. 
*) Weinland and A. Herz, Liebigs Annalen 400 (1913), 225. — 2%) Annal. de Chim. VII. 183 (1898), 120; 
Chem. Zentralbl. 1898, 1. 307. — A. Trillat, Compt. rend. 188 (1901), 822. — Otto and Verley, D. R. P. 97620; 
Chem. Zentralbl. 1898, II. 693. — *) Berl. Berichte 48 (1915) 32. — +4) Ibidem 231. See also C. Harries, 
ibidem 410. 
