120 ETHEREAL OILS. 



1)\' heating formic acid with oxide of lead is insohible in alcohol,^ 

 ■whilst basic acetate of lead prepared in a similar way is soluble 

 (the heating should be continued until the reaction is alkaline, 

 but not longer, as otherwise an acetate insoluble in alcohol might 

 be produced). Basic butyrate of lead is also soluble in alcohol, 

 but both the neutral and basic salt are greasy and sparingly soluble 

 in cold water. The same is the case with the ferric compound 

 obtained by precipitating an alkaline butyrate with a ferric salt 

 (avoiding an excess). (See also § 34.) 



i$ 140. Identificntion. — The mturnting jtoirer of a fattj' acid, a 

 knowledge of which may l^e of assistance in identifying it, can be 

 ascertained by titration with normal soda solution, or by esti- 

 mating the sodium, barium, lead or silver contained in the corre- 

 sponding salts. In certain cases a determination of the water of 

 rriistallkation may prove useful. 



By distilling the sodium salts with concentrated sulphuric acid 

 and absolute alcohol, the ethyl-salts of the acids may be prepared ; 

 they are not unfrequently of characteristic odour (acetate, lA^ty- 

 rate, valerianate of ethyl, etc.), by which, as also by their boiling- 

 points, they may sometimes be identified. 



§ 141. Optical Tests ; Soluhility in Alcohol. — For information with 

 regard to the optical testing of volatile oils see Buignet,- Franck,^ 

 Fliickiger,^ and Symes.^ 



I have ascertained that alcohol nuist jjossess the following 

 strengths to be miscible Avith certain ethereal oils in every propor- 

 tion : oil of turpentine, 96 per cent. ; fir, 96 per cent. ; juniper, 

 95 per cent. ; savin, 92 per cent. ; lemons, 97 to 98 per cent. ; ber- 

 gamot, 88 per cent. ; l)itter orange, 98 per cent. : caraway, 88 per 

 cent. ; peppermint, 86 to 87 per cent. ; oleum menthte crispse, 86 

 per cent. ; lavender, 88 per cent. ; rosemary, 82 per cent. ; sweet 

 marjoram, 82 per cent. ; cajei)ut, 91 per cent. ; sage, 85 per cent. ; 

 cloves, 74 per cent. ; cinnamon, 78 per cent. ; cubebs, 90 per cent. ; 

 fennel, 93 i)er cent. ; anise and rose, 93 to 94 per cent. ; balm, 90 



^ ' Barfoed, Lehrbuch der organischen qnal. Analy.se,' Kopenhagen, 1880. 



- Jüurn. de Pharm, et de Chim. [:3], xl. 2.">2, 1862 (Amer. Journ. Pharm. 

 xxxiv. 140). 



■' N. Jahr)), f. Pharm, xxvii. 1.31; xxix. 28. See also Mierzin.ski, 'Die 

 Fabrik, äth. Oule,' Berlin, 1872, and Flückiger'.s 'Pharm. Chemie,' Berlin, 

 1879, where the npecific gravities of certain ethereal oils will also be found. 



* Archiv d. Pharm. [.'3], x. 19:5, 1877 (Anur. .(ourn. Pharm. Ixxvii. 309). 



* Pharm. Journ. and Trans. [3], x. 20". 



