TEREBINTHINA \nL^LGARIS. 607 



sodium. This re-action proves the presence of a certain quantity of 

 oxygenated oils, not one of which has thus far been isolated. 



The turpentine oils, although agreeing in composition, exhibit a 

 series of physical differences according to their origin. One and the 

 same tree, indeed, yields from its several organs oils of different proper- 

 ties. The boiling point varies between 152° and 172° C. The sp. gr. 

 at mean temperatures ranges from 0-856 to 0-870. Greater differences 

 are exhibited in the optical properties, some varieties of the oil turning 

 the plane of polarization to the right, others to the left. This rotatory 

 power differs in many cases from that of the turpentine from which 

 the oil was derived.^ The odour of oil of turpentine varies with the 

 species from which it has been obtained. 



When crude turpentine is distilled with water, nearly the whole of 

 the oil passes over, while the resin remains. This resin is called Colophony 

 or Rosin. When it still contains a little water, it is distinguished in 

 English trade as Yelloiv Rosin ; when fully deprived of water, it 

 becomes what is called Transparent Rosin. That of deeper colour 

 acquired by a still longer application of heat, bears the name of Black 

 Rosin. 



Colophony softens at 80° C, and melts completely at 100' into a clear 

 liquid. At about 150° it forms a somewhat darker liquid, but without 

 undergoing a loss in weight ; at higher temperatures, it gradually de- 

 composes. Pure colophony has a sp. gr. of 1-07, and is homogeneous, 

 transparent, amorphous, and very brittle. At temperatures between 15° 

 and 20° C, it requires for solution 8 parts of dilute alcohol (0-883). On 

 addition of a caustic alkali, it dissolves in spirit much more freely. It 

 is plentifully soluble in acetone or benzol. 



The composition of colophony agrees with the formula C^H®^0* 

 By shaking coarsely powdered colophony with warm dilute alcohol, it is 

 converted into a crystalline body, Ahietic Acid, C^'H'^0^, — a result due 

 simply to hydration. Under such treatment, colophony yields 80 to 90 

 per cent, of abietic acid,^ and therefore consists chiefly of the anhydride 

 of that acid. This is probably the case with the resins of other conifers. 

 The living tree contains only the anhydride, for the fresh resinous juice 

 is clear and amorphous after the expulsion of the oil ; and when exposed 

 to the air it loses oil, takes up water and solidifies as the crystalline acid, 

 — a change which may easily be traced by the aid of the microscope, 

 in drops taken direct from the trunk. Amorphous colophony retains its 

 transparency even in a moist atmosphere, and appears to be capable of 

 passing into the state of abietic acid, only when the assumption of the 

 needful molecule of water is aided, in nature by the presence of the 

 essential oil, or artificially by that of alcohol. 



Colophony when boiled with alkaline solutions forms greasy salts 

 of abietic acid, the so-callen resin-soaps, which are used as additions 

 to other soaps. 



Siewert's Silvic Acid is regarded by Maly (ISG-i) as a product of the 

 decomposition of abietic acid ; and the Pimaric, Pinic and Silvio Acids 

 of former investigators, as impure abietic acid. Pimaric acid however, 

 which is the chief constituent of Galipot, appears to be decidedly 



^ For some particulars, see my notice in - Fliickiger in loc. cit. 1867. 36. — Most 



the Jahresbericht of Wiggers and Husemann chemists assign to this acid the formula 

 for 1869, p. 36.— F. A. F. C^oH^oO^, and call it mlvic and. 



