VANILLA, 163 
in stellate groups of crystals, possessing in a high degree the odour 
and taste of vanilla. 
Operating in this way the yield was very small, in consequence 
of the rapid resinification of the decomposition-product under the 
influence of the sulphuric acid, and in this state it was only slowly 
and partially attacked by the oxidizing mixture. It was found 
more easy and advantageous to operate directly upon coniferin. 
This was done by pouring an aqueous solution of coniferin into a 
warm mixture of potassium dichromate and sulphuric acid, and 
heating the whole together for several hours in a flask connected 
with an inverted condenser. After cooling, the liquid was filtered 
to remove a little resinous matter which was deposited, and then 
agitated with ether. Upon evaporating off this solvent a yellowish 
oil was obtained, which, after some days, formed a crystalline mass. 
By re-crystallizing this from hot water, and decolorizing with animal 
charcoal, fine crystals were obtained, identical in all respects with 
vanillin produced by nature *. 
In the course of the investigations made by Tiemann and Haar- 
mann in the laboratory of Dr. Hofmann at Berlin, it was found 
that on fusion with caustic potash, vanillin is converted into proto- 
catechuic acid, and on heating to 200° C. with hydrochloric acid, 
under pressure, it is decomposed into methyl chloride and _ proto- 
catechuic aldehyde, thus proving that vanillin is the methyl ether 
of protocatechuic acid or, to use the inconveniently long name 
applied to it by Dr, Tiemann, “ monomethylprotocatechuic 
aldehyde ” +. 
Protocatechuic acid is obtainable from various carbon compounds 
by fusion with caustic potash {, and its synthetical formation in 
various ways is of theoretical interest §. It is best prepared from 
East Indian Kino, as per note at foot | 
* Ber. Deutsch. chem. Ges. vil. pp. 609, 614, 
+ Ibid. vii. p. 608. 
{ Ann, Chem. Pharm. exxiv. p. 118, exxvii. p. 357, exxvili. p. 285, cxxx, 
p. 346, cxxxiv. p. 277, cxxxix. p. 78. 
§ Ibid. clii. p. 109, cliv. p. 364, clix. p. 252. 
|| Protocatechuie acid is most readily prepared from East-Indian Kino, which 
is obtained by making incisions in the bark of Pterocarpus Marsupium ; the sap 
flows out and dries to a dark red transparent mass. ‘One part of the finely 
powdered kino is gradually added to three parts of fused sodic hydrate, stirring 
the mixture constantly during the introduction of the kino and keeping the 
