158 ODOROGRAPHIA, 
servation of the beans in a dry place and in a box which is not 
hermetically sealed; also the removal from a warm locality to a 
cold one, which occurs when the produce is sent from the West 
Indies to Europe. The Réunion vanilla becomes frosted with 
crystals in about two months from the time of its preparation ; 
being soldered up in tin boxes in the colony, it is found frosted 
when the boxes are opened on their arrival in France. These 
crystals assume two distinct forms :—they appear either in very 
thin lamine or (which is generally the case) in needles so extremely 
fine and so close together as to appear like a minute hoary moul- 
diness or tufts of cotton—an aspect which, until the cause was 
understood, depreciated the value, but which is known to indicate 
the finest quality, or the ripest and most perfumed beans. VWanillin 
exists in the ripe fruit, but only appears on the surface under con- ' 
ditions favourable to its efflorescence. 
The reactions distinguishing vanillin from benzoic acid are :— 
Sesquichloride of iron gives to vanillin a dark violet coloration ; 
cold sulphuric acid gives to it a green coloration, and the hot acid 
colours it red. 
Quantitative Estimation of Vanillin in Vanilla-pods. 
The following method was devised by Tiemann and Haarman, 
and is abstracted from a paper read by them before the Berlin 
Chemical Society *. It is based upon the fact that vanillin, in 
common with other aldehydes, combines with acid sulphites of the 
alkalies to form compounds which are readily decomposable by 
acids. Vanillin being the only aldehyde present in vanilla, it is 
isolated without difficulty :— 
‘30 to 50 grams of vanilla cut small are placed with 1 to 14 litre 
of ether in a large stoppered bottle and left in contact during from 
6 to 8 hours, being frequently shaken. The clear liquid is then 
decanted off and filtered through a plaited filter into a large flask. 
A fresh quantity of 800 to 1000 ce. c. of ether is introduced into the 
stoppered bottle, shaken very frequently, and, after from 1 to 2 
hours, filtered. The operation is repeated for a third time with 500 
to 600 c.c. of ether. The now exhausted-fragments of vanilla are 
thrown upon the filter with the very last portion of the third quan- 
tity of ether, and then washed with a small quantity of fresh ether. 
After this treatment the fragments of vanilla are absolutely taste- 
* Ber. der Deutsch. chem. Ges. viii. p. 1115, and Pharm. Journ. [5] vi. p. 603, 
