120 ETHEREAL OILS. 



by heating formic acid with oxide of lead is insohxble 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 saJt 

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



§ 140. Identification. — The saiwating power of a fatty acid, a 

 knowledge of which may be 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 coire- 

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

 erystaUization may prove useful. 



By distilling the sodium salts with concentrated sulphuric acid 

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

 fchey are not unfrequehtly of characteristic odour (acetate, buty- 

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

 points, they may sometimes be identified. 



§ 141. Optical Tests ; Solubility in Alcohol. — For iijformation with 

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

 Fliickiger,* and Symes.'' 



1 have ascertained that alcohol must possess the following 

 strengths to be miscible with certain ethereal oils in eveiy 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. ; bitter orange, 98 per cent. : caraway, 88 per 

 cent. ; peppermint, 80 to 87 per cent. ; oleum meiithas crispse, 86 

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

 marjoram, 82 per cent. ; cajeput, 91 per cent. ; sage, 85 per cent. ; 

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

 fennel, 93 per cent. ; anise and rose, 9.5 to 94 per cent. ; balm, 90 



^ ' Barfoed, Lehrbuch der, organiachen qual. Analyse,' Kopenhagen, 1880. 



2 Journ. de' Pharai. et de Chim. [3], xl. 252, 1862 {Amer. Journ. Pharm. 

 xxxiv. 140). 



' N. Jahrb. f. Pharm. xxvii. 131 ; xxix. 28. See also Mierzinski, ' Die 

 Pabrik. ath. Oele,' Berlin, 1872, and Fiiickigers 'Pharm. Cbemie,' Berlin, 

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



• Archiv:d. Pharm. [3], x. 193, 1877 (Amer. Journ. Pharm. Ixxvii. 309). 



' Pharm. Journ. and Trans. [3], x. 207. 



