The crude American turpentine is a viscid liquid of about the consistence of honey, but varying to a soft solid, known as gum, thus, according to the amount of exposure which it has undergone, it contains about 10 to 25 per cent. of "spirits," to which the name of turpentine is commonly given, the rest being resin, or as it is usually called, rosin.
In Liverpool almost all the spirits of turpentine comes from America, so that it is almost impossible to get a sample of French.
The terpene from American turpentine is called austraterebenthene. It possesses dextro-rotatory polarization of +21.5. Its density is 0.864. Boiling point 156° C.
In taking the boiling point of a commercial sample of spirits it is necessary to wait until the thermometer becomes steady. Not more than 5 per cent. should pass over before this takes place, and then there is not more than two or three degrees of rise until almost all is distilled over.
The liquids of lower boiling point do not appear to have been much studied. In French spirits they seem to be of the same composition as the main product, but with more action on polarized light.
French spirits of turpentine is mainly composed of terebenthene. The boiling point and sp. gr. are the same as those of the austraterebenthene, but the polarization is left handed and amounts to -40.5.
Isomeric modifications. Heated to 300° C. in a sealed tube for two hours, it becomes an isomeric compound, boiling at 175° C., while the density is lowered, being only 0.8586 at 0° C. The rotatory power is only -9°. It oxidizes much more rapidly. It is called isoterebenthene and has a smell of essential oil of lemons.
By the action of a small quantity of sulphuric acid, among other products terebene is formed. It has the same boiling point and sp. gr. as terebenthene, but is without action on polarized light. Austraterebenthene forms similar if not identical bodies.
Polymers. One part of boron fluoride BF3 instantly converts 160 parts of terebenthene into polymers boiling above 300° C., and optically inactive. H2SO4 does the same on heating and forms diterebene C20H32.
Terchloride of antimony does the same, and also produces tetraterebene C40H64, a solid brittle compound formed by the union of four molecules of C10H16. It does not boil below 350° C. and decomposes on heating.