236 ODOROGRAPHIA. 
in chloroform, carbon disulphide, volatile and fatty oils, and con- 
centrated sulphuric acid. 
It is characteristic of benzoic acid that certaim impurities, even 
when they are present in extremely small quantities, alter its 
physical properties to a very considerable extent. 
Many varieties of benzoin contain cinnamic acid in addition to 
benzoic acid, and frequently only the former *. Both these acids 
occur either free or in the form of ethereal salts, together with 
other aromatic compounds, in Tolu balsam, Peru balsam, Mecca 
balsam (Balsamodendron Opobalsamum et Gileadensis), Myrrh 
(B. Myrrha), liquid Styrax, acaroid resin (Xanthorrhea hostilis), 
Dragon’s blood, and other resms. Benzoic acid has also been 
found in the oil of Ylang-Ylang (Cananga odorata), in plums 
(Prunus domestica chlorocarpa), and the cranberry. It also occurs 
in vanilla, the fruit of the clove-tree, the seeds of the spindle-tree 
(Huonymus Europeus), and the root of the sweet flag (Acorus 
calamus). 
Fourcroy and Vauquelin found, in 1797, that the urine of grami- 
nivora contains benzoic acid; and Liebig, in 1829, showed that a 
new nitrogenous acid, which he named hippuric acid, splits up 
when the urine is allowed to stand, yielding benzoic acid. Ac- 
cording to some observers, however, benzoic acid frequently occurs 
along with hippuric acid in the urine, and it has been found in a 
gland in the beaver}, and in the kidneys of the ox{. It is 
probable that in all cases the acid is formed by the decomposition 
of hippuric acid. It also occurs in coal-tar. 
Benzoic acid, C,H;.COOH, was formerly prepared exclusively 
from gum benzoin by sublimation; thus obtained it always 
contains a small amount of an ethereal oil, which gives it its’ 
peculiar smell. In order to prepare it in this way, the coarsely 
powdered resin is heated to about 170° in a flat iron vessel ; this is 
covered with filter-paper, and fitted with a conical cap of strong 
paper in which the acid sublimes. ‘This acid is commercially 
called “ English benzoic acid” or “ Benzoim-benzoice acid.” 
A second process for procuring it from its natural source 
(Scheele’s process) consists in boiling a mixture of equal weights 
* Kolbe, Ann. Chem. Pharm, cxix. p. 136. 
+ Ann. Chem. Pharm. lxvii. p. 360. 
J} Chem. Centralbl. 1861, p. 241. 
