124 ETHEBEAL 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 C^^H^g, 

 the 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 Avith certain oils. Some 

 oxygenated oils (carvol of cummin oil) yield crystalline s«/pM?/f/ya^es 

 when mixed with alcoholic solution of sulphide of ammonium, from 

 which the oil may be separated l)y decomposition with potash. ^ 

 If hydrochloric acid gas is passed through ethereal oils, 

 crystalline or liquid hjdrochlorates are not unfrequently produced, 

 which may l^e characteristic of the oil acted upon. The NOCl 

 group sometimes combines with hydrocarbons of the terpene 

 series to form compounds of the formula C^qHjqNOCI, and, 

 according to Tilden, this reaction also maj'' be e'mployed in dis- 

 tinguishing ethereal oils. Tilden ^ ol)tained 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 Crahe^ and Tomlinson.^ 



§ 143. Fractioncd distillation. — Linnemann's apparatus^ (fig. 6) 

 is very servicealde 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 tul)e, B, is fused on at an 

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

 Just l)eneath the junction, and at a distance of 20 and 25 cm. from 

 the end, l>ull:)s are blown. At the upper end a thermometer is 

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

 of the tul)e 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 

 vai)our of more easily volatile liquids. Smaller ap})aratuses of 

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



For distillation in a ]mrtial vacuum the apparatus represented in 



' Compare Jahre.sb. f. riiarni. 468, 1867. 



- Pharm. Joiirn. and Trans, [-i], viii. 188. 



•' Pharm. Journ. and Trans. [;SJ, v. 242. •* Iliid. v. 280. 



•'' Annal. d. Chem. und Pharm, clx. 195, 1872. 



