182 ODOROGRAPHIA. 
_ prussic acid can be made by dipping bibulous paper in fresh 
tincture of guaiacum, then drying and dippimg in an aqueous 
solution of cupric sulphate (1 in 2000) and once more drying. 
The paper will become intensely blue if moistened and afterwards 
dipped into oil containing prussic acid. 
There are other chemically prepared compounds having the 
odour of bitter almonds, such as Nitrobenzene, Nitrotoluene, Meta- 
nitrotoluene, &c. 
MIRBANE. 
Nitrobenzene, C,H;NO,, is used in perfumery as a substitute for 
oil of bitter almonds. 
Nitrobenzene can be readily distinguished from oil of bitter 
almonds by the following test :— 
Pour a few drops of each on a plate and add a drop of strong 
sulphuric acid. The oil of almonds acquires a rich crimson 
colour with a yellow border,—the nitrobenzene produces no colour. 
Also it yields no Prussian blue when mixed with sulphate of 
iron, alcohol, and potash. 
It was first introduced in commerce by Collas under the name 
of “Essence of Mirban,” and incorrectly called “ artificial oil of 
bitter almonds.” In 1874 a process was patented by Mansfeld 
for its preparation from coal-tar. It is now prepared on a very 
large scale and employed for a variety of purposes. 
To prepare it in small quantities, equal parts of fuming nitric 
acid and benzene are gradually mixed. The apparatus consists of 
a large glass worm, the upper end of which is divided into two 
branches gradually dilating so as to form two funnel-shaped tubes : 
into one of these the nitric acid is poured, and into the other the 
benzene. These bodies meet at the point of junction of the two 
tubes, and the rate of their flow is regulated by an appropriate means. 
Chemical reaction instantly takes place and the new compound is 
cooled in its passage through the worm, which is refrigerated for 
the purpose. It has then only to be washed with water or a very 
weak solution of carbonate of soda or caustic soda for the process 
to be complete. 
It is a light yellow, strongly refractive liquid, having at 0° a 
sp. gr. of 1°200. It has a peculiar smell, similar to that of bitter 
