A comparison of the course of careful fractionations of American and French turpentine oil, has been made readily possible by two tables published by B. Ahlstrom and 0. Aschan3). These tables reveal not only the amounts that distil over for each degree, but also record the density and specific rotation of each fraction.
Approximate amount in grams
153 to 155°
156 ,, 157°
157 ,, 158°
French Turpentine Oil:
Approximate amount in grams
153 to 155°
155 „ 156°
- 40,51 °
156 „ 157°
157 „ 158°
158 „ 159°
159 „ 160°
160 „ 161°
161 „ 162°
162 „ 163°
163 „ 173°
Because of the oxygenated substances and polymerization products which they contain, the boiling temperature of old, resinified turpentine oils is considerably higher. In as much as the pine tar oils contain dipentene, sylvestrene and other sub1) Coste [Analyst 33 (1908) 219 to 230; Chem. Zentralbl. 1908, II. 731] demands that when 100 cc. are distilled from a 180 cc. Ladenburg fractioanting flask with a shortened Anschutz thermometer, nothing shall come over below 155°, 70 p. c. between 155 and 160°, and 95 p. c. between 155 and 180°.
2) Pharm. Review 15 (1897), 7.
3) Berl. Berichte 39 (1906), 1443, 1444.
stances, the percentage that distils over above 162° is greater with these oils.
Evaporation Residue. Upon evaporation turpentine oil is almost completely volatile. An abnormal, non-volatile residue not contained in the original oil, may, however, be encountered: on the one hand products of decomposition and polymerization may result where too high a temperature is used; on the other hand, slow evaporation due to too low a temperature may result in oxidation products.
If the evaporation residue is determined on a water bath in the ordinary manner, results that are too high are obtained, since the oil oxidizes most readily at water bath temperature and hence resinifies considerably. For this reason H. Herzfeld1) determines the evaporation residue at a temperature approximating that of the boiling temperature of the oil. Into a platinum dish, completely imbedded in a sand bath and heated to 155°, 5 cc. of oil are slowly transferred. After vapors cease to be given off, the dish is heated for 15 minutes longer. The results thus obtained vary but little. Considerable, however, are the differences in the results obtained by this method as compared with those obtained by the waterbath method.
In order to avoid ignition of the instantaneously formed turpentine vapors, Kollo2) has slightly modified the technique of the method. He places the platinum or nickel dish inside of a tin ring about as broad as a finger. The ring causes a more rapid evaporation at the point of contact, every drop evaporating as it is added, thus accomplishing the end sought more quickly and securely. The dish should project but slightly from the ring, is imbedded in sand up to the ring, and is heated to 155°. With the aid of a separating funnel, the tube of which is twice bent at right angles and drawn out to a point, the oil is added very slowly (100 drops per minute).
H. Wolff3), who has frequently observed a creeping of the last portion of the oil, avoids this evil by placing a cylinder over the evaporating dish. This cylinder, made of tin, should be about 5 cm. high and of a diameter exceeding that of the evaporating dish by about 1 cm. It is imbedded in the sand to the extent of about 1/2 cm.
1) Chem. Revue Fett- u. Harzind. 1909, 174; Pharm. Zentralh. 51 (1910), 72.
2) Pharm. Zentralh. 51 (1910), 154.
3) Farbenzeitung 16 (1911), 2746; Chem. Zentralbl. 1911, II. 1181.
In the case of a normal oil the residue thus determined does not exceed 1 p. c. However, in the case of an old oil, or of one adulterated with high boiling petroleum fractions, the residue is larger. As to how such an oil should be further investigated see p. 33.
Flash Point The flash point of turpentine oil is recorded at 32o1) to 35°2) to 37,7 °3). It must be remembered that the flash point will vary according to the apparatus used. Hence the statements as to the flash point that do not likewise record the apparatus employed in its determination are of little value. Apparently the above data pertain to a closed apparatus (Abels' petroleum tester, the apparatus of Pensky-Martens). The flash point of turpentine oil, when determined in an open apparatus, such as is employed in the examination of lubricating oils (Comp. Lunge-Berl, Chemisch-technische Untersuchungsmethoden,6th. Berlin, vol.3. p. 611), lies in the neighborhood of 41 to 42°. However, conclusions as to the purity of the turpentine oil are not warranted at present, for the observations are still too meagre. This much, however, seems apparent that the normal flash point is lowered by the addition of petroleum or low boiling hydrocarbons.
Acid Content. All crude oil distilled from turpentine contains normally small amounts of formic acid, acetic acid and resin oil. The last is due to the initial stages of pyrogenous decomposition, which sets in toward the end of the distillation when the colophony is heated to a certain point. The resin oil that passes over always contains some colophony4). These admixtures (rosin oil and colophony) have been designated normal adulterants ("adulterants normaux") by Vezes1). The maximum in commercial oil should not exceed 2,5 p. c. and the acid value should not exceed 1,52). Inasmuch as the average acid value of colophony is 1703), an acid value of 1,5 corresponds to 0,0088 g. colophony in 1 g. of oil of turpentine, or 8,8 g. in 1 kg = 0,88 p. c.
1) Long, Chem. Zentralbl. 1892, II. 174. - Journ. analyt. and appl. Chemistry VI. No. 1; Journ. Parfum. et Savonn. 24 (1911), 113.
2) Vezes, Sur la definition de l'essence de terbenthine commerciale-ment pure. Bordeaux 1910, p. 2.
3) L. M. Nash, Analyst 36 (1911), 577; Chem. Zentralbl. 1912, I. 448.
4) Comp. also Vezes and Eustache, Sur un mode simple de dosage de fa colophane dans l'essence de terebenthine et dans l'huile de resine. Bordeaux 1901.