VANILLA. 167 
Protocatechuic acid, produced from the above. 
Dimethylprotocatechuic acid *, prepared by heating the above 
with caustic potash, methyliodide, and wood spirit f. 
When this last compound (which is identical with veratric acid) 
is heated with dilute hydrochloric acid in a closed vessel to 130°- 
140° C., among the products of decomposition is found mono- 
methylprotocatechuic or vanillic acid, of which vanillin is the 
corresponding aldehyde. 
The retrograde conversion of the acid into the aldehyde can be 
effected by the dry distillation of an intimate mixture of vanillate 
and formate of calcium. An oily distillate is obtained consisting 
of guaiacol and a small quantity of vanillin. If an ethereal 
solution of this distillate be agitated with a concentrated aqueous 
solution of sodium bisulphite, the latter, after decomposition with 
sulphuric acid, will yield the vanillin to ether. By crystallization 
from hot water it is obtained im a perfectly pure state. The 
other products of the decomposition of vanillic acid being car- 
bonic acid and guaiacol, this latter corresponding in every respect 
with that obtained from beech-wood tar f. 
The specification of Dr. Haarmann’s English Patent, dated 
Feb. 25, 1874 (No. 709), claims the following processes :—“ In 
order to obtain the artificial production of vanillin, by means of 
coniferin or the sap of plants belonging to the species of conitera 
as an extract of all those parts containing coniferin, take either, 
first, coniferin ; or, secondly, the sap of the plants which has been 
purified from albumina and other impurities; or thirdly, an 
extract of the parts; or fourthly, the products obtained from 
* Dimethylprotocatechuic acid, identical with veratric acid, exists in the 
seeds of Veratrum Sabadilla. It can also be prepared by shaking up 1 part of 
methyl-eugenol with 10 to 15 parts of water, and a solution of 33 parts of 
potassium permanganate in 20 to 30 parts of water heated to 8U°-90° C, 
gradually added. The filtrate is concentrated by evaporation and precipitated 
by hydrochloric acid (Ber. Deutsch. chem. Ges. ix. p. 937). Veratric acid dis- 
solves in 2100 parts of water at 14°, and in 160 parts at 100°, and crystallizes 
from a concentrated solution at a temperature above 50° in anhydrous needles, 
while crystals containing a molecule of water are obtained from very dilute 
solutions at any temperature below this. It melts at 174°-175° and can be 
sublimed. It dissolves readily in alcohol and ether; ferric chloride produces 
no coloration. 
+ Ber. Deutsch. chem. Ges. viii. p. 514. 
{ Ibid. viii. p. 1124. 
