218 ODOROGRAPHIA. 
are still liquid in the presence of a resin-content of 30 per cent. 
Two estimates of every oil ought to be made, of which the average 
should be taken. Both should accurately agree, or at most show 
a difference of 1,2, or 4 per cent. 
The following tests are given by E. Hirschsohn in the ‘ Journal 
of the Chemical Society’ (and reprinted in the Pharm. Journal, 
May 2, 1891). One volume of the oil should give a clear or merely 
opaline solution with three volumes of 70-per-cent. alcohol at 15° ; 
a turbidity or sediment indicates the presence of petroleum or of 
foreign ethereal or fatty oils, or of a large excess of colophony. 
Also, when the alcoholic solution is added drop by drop into half 
its volume of a cold saturated solution (saturated at the tempera- 
ture of the room) of lead acetate in 70-per-cent. alcohol, no pre- 
cipitate should be produced, otherwise colophony or a similar resin 
is present. Oils without any addition of resin do not become 
turbid on applying this test. Even old cassia oils with their slightly 
increased content of cimnamic acid remain quite clear. However, 
some old cassia oils that have been kept in badly closed vessels 
may possibly precipitate cinnamate of lead. This test with acetate 
of lead is particularly commended when little material is available 
for the investigation. 
To detect the adulteration of oil of cassia by oil of cloves, a drop 
of the oil should be heated on a watch-giass. Genuine cassia 
evolves a fragrant vapour possessing but little acridity ; when, 
however, clove oil is present, the vapour is very acrid and excites 
coughing. With fuming nitric acid, cassia merely crystallizes ; if 
clove be present it swells up, evolves a large quantity of red vapour 
and yields a thick reddish-brown oil.. Cassia oil when pure 
solidifies with concentrated potash, but not when mixed with clove 
oil. 
It has been noticed that oils of cassia and cinnamon may be 
highly adulterated with resin oils and still pass the tests of the 
German Pharmacopeeia *. 
With nitric acid sp. gr. 1°45 at 15°, or with 1:50 acid at 6°, 
both the pure and impure oils give crystals without development 
of heat ; however, with the 1°50 acid at 15°, both react violently, 
with development of heat and without the formation of crystals. 
Therefore the P. G. test, as neither the sp. gr. nor the temperature 
* Chem. Zeit. xiii, pp. 1406-7, and Journ. Chem. Soc. Apr. 1890. 
