144 
PROXIMATE PRINCIPLES. 
not unite with water. They are divided into Fixed and Vola- 
tile. The Fixed oils are thick and have little odour. 
The oil of sweet almonds, and olive oil grow thick and opaque 
by being exposed to the air. 
The Oil of Flax Seed, called linseed oil, and some other oils, 
dry without losing their transparency ; it is this quality which 
renders linseed oil so valuable to painters. 
The Volatile oils, are distinguished from the fixed oils by 
their aromatic odors, and their tendency to fly off, from which 
circumstance the term volatile is derived. Some of these oils 
are those of the orange, lavender, rose, jasmine, peppermint, and 
wintergreen. These oils are sometimes greatly reduced by being 
mixed with alcohol, and are then called essences. The volatile 
oils may be found in a great variety of plants, particularly those 
of the Labiate family. 
The Aroma, or aromatic property, consists chiefly of the 
odors which are exhaled from plants, containing volatile oil ; 
it is this oil which throws out the aromatic odour of the ginger 
plant, of the myrtle, rose, and other sweet scented plants. 
Aromatic plants are much more common in hot, than cold coun- 
tries ; most of our aromatic spices are found in the equatorial 
regions. 
Wax is found on the surface of the fruit of the bay-berry, 
(Myrica cerifera.). Beeswax is an animal production, made 
by the bees from pollen or farina of plants. 
Camphor has much analogy with the volatile oils ; it is an 
extract from the Laurus camphora, or camphor tree of Japan. 
Resin exudes from the pine, and some other trees ; it is dry, 
insoluble in water, but soluble in alcohol and very inflammable. 
The people in new countries often use, as a substitute for 
lamps, pine knots, which, abounding in resin, burn with a bright 
flame. 
The difference between resin and the volatile oils, appears to 
consist in the action of oxygen upon the resin ; for the oil in ab- 
sorbing oxygen from the air, passes into the resinous state. 
Resins mixed. with volatile oils form balsams ; thick, odorous, 
and inflammable substances of this kind are the balsam copaiva, 
dragon’s blood, which, notwithstanding its terrific name, is but 
the simple extract of a plant, (Draccena draco ;) the balsam of 
Tolu is the extract of the Toluifera balsamum. 
These resins are sometimes mixed with gums, they are then 
called gum-resins ; of this kind are gamboge, a»safcetida, guaia- 
cum, aloes, an extract from the Aloe perfoliata. These gum- 
resins in flowing from vegetables are sometimes white and liquid 
Third order, oils, &c. 
