SCIENTIFIC AND OTHER NOTES ON ESSENTIAL OILS. 41 
difficult to check, seeing that the author has not given the slightest indications as to 
the properties of the original oil. 
Wintergreen Oil. In our Report of April 1914 (page 98) we mentioned a colour 
test published in the Perfumery and Essential Oil Record for distinguishing natural from 
attificial wintergreen oil. The test is carried out as follows: 5 drops of the oil to 
be tested are mixed with 5 drops of a 5 p.c. alcoholic vanillin solution and 1 cc. of 
alcohol, and well shaken. Next 2 cc. of concentrated sulphuric acid are added, and 
the mixture is again well shaken. Natural oil produces an intense crimson colour, while 
artificial oil yields a yellow colour. 
Since then a few further colour reactions have been recommended for the same 
purpose by G. N. Watson and L. E. Sayre’). In one of the tests the oils are mixed 
with an excess of sulphuric acid. It is claimed that gaultheria oil will produce an 
intensely red, birch-bark oil a yellowish or faintly red, and artificial methyl salicylate 
no colouring at all. A second test consists in a few drops of the oil to be tested 
being mixed with 2 cc. of concentrated sulphuric acid and 2 drops of a saturated 
alcoholic solution of heliotropin. In this case gaultheria oil will cause a pronounced 
red colour, which, upon addition of alcohol, is converted into a dark violet colour. 
In the case of birch bark oil the colour shades are similar but somewhat less pro- 
nounced, whereas the artificial product yields a yellow colour, which, however, is to 
be attributed solely to the influence of sulphuric acid on heliotropin. The following 
is recommended as a still better test, capable above all of distinguishing between 
gaultheria and birch bark oil: 1 cc. of the oil is mixed with 2 cc. of concentrated 
sulphuric acid, 1 cc. of a saturated aqueous solution of chloralhydrate being added. 
It is claimed that with this test gaultheria oil will develop a dark green coloration, 
the dark green oily layer showing above a lighter green aqueous zone. This becomes 
more pronounced when 2 to 3 cc. of water are added. Birch bark oil yields a dark 
violet oil layer, whereas methyl salicylate affords no coloration at all, or else a faint 
violet shade which becomes noticeable only after prolonged standing. 
In connection with these reactions a well known means of distinction between 
natural and artificial oil is called to mind. The natural oil, on being shaken, shows a 
slight froth at the top which lasts for a short while, the artificial oil, however, shows 
no froth at all. It is also claimed that a rise in the temperature, when mixed with 
sulphuric acid, only occurs in the case of natural oils. This contention, however, is 
not correct, as we have ascertained ourselves and as was to be expected. 
Opinions as to the value of the tests recommended by Watson and Sayre may 
differ. Apart from the fact that colour reactions are always a make-shift of doubtful 
value, above-mentioned tests, as we had occasion to convince ourselves in guaranteed 
pure oils distilled by ourselvess, can only be used for distinguishing between natural 
and artificial oil at most. When tried with gaultheria or betula oil, the reagents 
produced either identical results, or else the differences were so slight as to permit 
of no conclusions whatsoever. Generally speaking it could be established that the 
colour shades were a little more pronounced with gaultheria oil than with betula oil, 
but we failed to observe positive differences in the colouring, not even with the 
chloralhydrate test, where we waited in vain for the green colouring of gaultheria oil. 
In this case both natural oils showed brown coloration, which was converted into a 
turbid violet when water was added. Artificial oil. remains colourless in this reaction, 
1) Journ. Amer. Pharm, Assoc. December 1914, 1, 658; Pharmaceutical Journ. 94 (1915), 281. 
