BALSAM OF MECCA. 273 
is put up in square leaden bottles containing about 250 grammes, 
but is, as a rule, adulterated, and many chemists even sell Chian 
turpentine or Canada balsam instead of it. Oil of sesamum is 
likewise used as an adulterant. 
According to Prosper Alpinius* the true balsam is at first 
turbid and white, of very strong pungent smell, like that of 
turpentine, but much sweeter, with a bitter, acrid, astringent taste ; 
upon being kept for some time it becomes thin and limpid, of a 
greenish hue, then of a golden yellow, and at length of the colour 
of honey. A drop of the balsam, when let fall into a vessel con- 
taining water, at first sinks to a certain depth, and then rising to 
the surface, instantly and completely spreads out into a thin 
nebulous film, which under a magnifying-glass presents the 
appearance of an infinite number of little globules uniformly 
spread over the entire surface of the water. After about a quarter 
of an hour this film solidifies, by reason of the rapid evaporation 
of its volatile oil; it can then be lifted out entire on the point of 
a pencil. This invariable property was first observed by Prosper 
Alpinius + ; it is of great exactness and is one of the best tests of 
the purity of the balsam. It was confirmed by Guibourt on 
experimenting with a sample which he had reason to believe was 
quite pure, aud with which sample he made the following further 
observations :—The balsam thickens with age, becomes more brown 
in colour, and does not rise so quickly and spread out on the surface 
of water; a natural result of resinification and loss of volatile oil. 
When rubbed on the hand, the balsam rapidly loses its volatile oil 
and becomes very sticky. Dropped on paper it spreads a little, 
but does not penetrate or render the paper transparent. After 
twelve hours of exposure to the air, the drop of balsam becomes 
so adhesive that on doubling the paper in two it becomes difficult 
to separate the sheet without tearing it. On being triturated 
with an eighth of its weight of oaleied magnesia it does not 
solidify as do the turpentines of pines and several balsams. Five 
grammes of balsam mixed with 30 grammes of 90 per cent. alcohol 
form a liquid white as milk, which only becomes transparent after 
being left standing for 8 or 10 days; a glutinous matter being 
then deposited which consists of insoluble resin. This resin 
* ‘Dialogue du Baume,’ traduction d’Antoine Collin, Lyon, 1819. 
+ Ibid. p. 61. 
ue 
