124 ETHEREAL OILS. 



layer ; with a mixture of both acids, blue. Gurjun-balsam oil 

 behaved similarly, and oil of cubebs also turned blue with a 

 mixture of both acids. 



Solid iodine added to ethereal oils produces somewhat varying- 

 effects. With some oils, especially terpenes of the formula CjjHjg, 

 t?ie action is very energetic, and accompanied by evolution of both 

 light and heat, whilst with others nothing of the kind is observ- 

 able. Chromic acid also reacts explosively with certain oils. Some 

 oxygenated oils(carvolof cummin oil) yield cvystfiWiae sidjihhydraies 

 when mixed with alcoholic solution of sulphide of ammonium, from 

 which the oil may be separated by decomposition with potash. ^ 

 If hydrochloric acid gas is passed through ethereal oils, 

 crystalline or liquid hydrocJdorates are not unfrequently produced, 

 which may be characteristic of the oil acted upon. The KOCl 

 group sometimes combines with hydrocarbons of the terpene 

 series to form compoimds of the formula CjjHjgNOCl, and, 

 according to Tilden, this reaction also may be employed in dis 

 tinguishiiig ethereal oils. Tildeu^ obtained crystalline compounds 

 with French and American oil of turpentine, with oil of juniper, 

 sage, caraway, bitter orange, bergamot, and lemon. 



For the use of cohesion, figures in identifying the various 

 ethereal oils see Kate Crane^ and Xomlinson.* 



§ 143. Fractional distillation. — Linnemann's apparatus* (fig, 6) 

 is very serviceable in fractionally distilling ethereal oils (§ 30). 

 A is a tube of about 40 cm. in length and 1 cm. in diameter ; at 

 about 32 cm. from one end a second tube, B, is fused on at an 

 angle of about 80°, so that it can be connected with a condenser. 

 Just beneath the junction, and at a distance of 20 and 25 cm. from 

 the end, bulbs are blown. At the upper end a thermometer is 

 introduced, the bulb of which .should.be in C. In the lower part 

 of the tube about 8 cup-shaped pieces of platinum gauze are 

 inserted. These are intended to receive the condensing vapour 

 from the liquids of higher boiling points and wash, as it were, the 

 vapoiiT of more easily volatile liquids. Smaller apparatuses of 

 30 or 25 cm. in height may be used for special purposes. 



For distillation in a partial vacuum the apparatus represented in 



^ Compare -lahresb. f. Pharm. 468, 1867. 



* Pharm. Jonrn. and Trans. [3], viii. 188. 



' Pharm. Journ. and Trans. [3], v. 242. ■• Ibid. v. 280. 



« Annal. d. Chem. und Pharm. clx. 195, 1872. 



