DR. JOHN STENHOUSE ON VEGETABLE PRODUCTS FROM INDIA. 
149 
to yield, as Rigaud states, only oxalic acid. I had no opportunity of trying escule- 
tine, but it is stated by those who have investigated it to yield only oxalic acid. 
I will conclude this account of datiscine by proposing the following practical 
application. As is well known, the colouring matter of madder when boiled with 
dilute sulphuric acid is changed into sugar and garancine, a new dye-stuff, which 
for many purposes is found superior to that originally present in the madder. 
Within the last twelve months, Mr, Lieshing, by treating the colouring matters in 
weld and quercitron bark with dilute sulphuric acid, has resolved them into new 
colouring matters, which are but slightly soluble in water, and are found nearly three 
times more powerful as dye-stuffs than the original colouring matters from which 
they had been produced. As datiscine, when boiled with dilute sulphuric acid, under- 
goes a perfectly similar transformation, being resolved into sugar and datiscetine, 
which has a much higher colouring power than the datiscine which has produced it, 
I have not the least doubt that silk dyers, who may hereafter employ solutions of 
Datisca cannahina, will find it highly advantageous to convert their datiscine into 
datiscetine by boiling it with dilute sulphuric acid ; as the process is an extremely 
simple one, and as the datiscetine, from its sparing solubility in water, can be very 
readily obtained in a state of comparative purity. 
Ptychotis Ajowan. 
The Ptychotis Ajowan is an umbelliferous plant, well known in India for its aro- 
matic and carminative properties. Its seeds, which very much resemble in appear- 
ance those of the caraway, only being much smaller, have a very agreeable odour, 
resembling oil of thyme. 
On distilling these seeds repeatedly with water, the essential oil is very easily 
obtained, amounting to between five and six per cent, of the weight of the seeds. 
This oil has a light brown colour, and possesses an agreeable aromatic odour. Its 
specific gravity is 0'896 at 12° C., and upon leaving the oil for some time in an open 
dish to spontaneous evaporation, the temperature at the time being comparatively 
low, large beautiful crystals were deposited, which on examination were found to 
be identical with the stearopten brought from India by the late Dr. Stocks, and 
described by me in a short notice published in the number of the ‘Pharmaceutical 
Journal’ for December 1854. When the crude oil is submitted to distillation, it 
begins to boil at 160° C., the thermometer rising rapidly to 174° C. The thermo- 
meter then rises to 220° C., and the oil which comes over at this temperature crystal- 
lizes on cooling. The residue, which does not immediately crystallize, on remaining 
at rest for some time, solidifies into a crystalline mass, the crystals having precisely 
the same form as those obtained by spontaneous evaporation, and amounting, in 
weight, to from one-third to one- fourth of the crude oil. As it seemed probable from 
these experiments, therefore, that Ptychotis oil, like many other essential oils, is a 
WDCCCLVI. 
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