600 
ADULTERATIONS IN ESSENTIAL OILS. 
“III. The fatty oils render essential oils rather thick, and 
facilitate the formation of air-bubbles on the surface. A pure 
essential oil mixed with eight times its weight of alcohol, sp. 
gr. 0823, dissolves entirely, whilst the fat oil remains intact, 
and separates, provided it be not castor oil, which is soluble 
in alcohol, 
“ A fatty oil mixed with a volatile oil gives, when heated, a 
very definite stain on white paper, which is permanent. 
“IV. An admixture of resin also communicates a stain to 
paper, but this stain is readily removed by alcohol, which 
does not affect the mark formed by a fatty oil. 
“V. Those adulterations which consist in mixing essential 
oils with other essences of a less price, are often very difficult 
to detect. 
“ Lately, two reactions have been discovered which admit 
of the division of the volatile oils into two great groups. 
“ It is known that some contain no oxygen, but the greater 
number do contain that element; to determine to which 
of these groups a given oil belongs, Mr. Hope recommends 
the following plan to be adopted:—Precipitate a salt of copper 
with nitro-prusside of sodium, collect the precipitate on a 
filter, wash and dry it at 100° C. The precipitate is then used 
in very small proportion (a fragment about the size of a pin's 
head), which is mixed in a glass tube with a few drops of the 
oil to be tested, boil for a few minutes, and then allow it to 
stand. If the essential oil contains no oxygen, as, for instance, 
oil of turpentine, a green or greenish-blue precipitate will be 
observed, whilst the supernatant oil is colourless or slightly 
yellow. With oils which do contain oxygen, and which have 
not been mixed with other oils free from this element, the 
nitro-prusside of copper becomes black, gray, or brown, 
whilst the supernatant oil assumes a darker shade than in 
the first instance, becoming of a brownish-yellow or green 
colour. 
“The essential oils of orange, citron, juniper, and of savin, 
behave like oil of turpentine. 
“ The essential oils of cumin, fennel, lavender, peppermint, 
balm, majoram, sage, absinthe, cajeput, sassafras, and rue, 
contain oxygen." 
