120. FIXED OIL, ETC. 99 



IX. 



SPECIAL METHODS FOR THE ESTIMATION OF CERTAIN CONSTI- 

 TUENTS OF PLANTS, SUPPLEMENTARY NOTES TO THE PRE- 

 CEDING EXPERIMENTS. 



FATS AND THEIR CONSTITUENT ; CHOLESTERIN, FILICIN, ETC. 



120. Estimation of Fixed Oils. For reasons given in 8, I 

 recommended the use of benzene some twenty years ago 1 for 

 extracting fixed oils. Petroleum spirit, which I subsequently 

 introduced for the same purpose, has the advantage over benzene 

 of being more volatile and possessing a lesser solvent power for 

 resins, etc. (Cf. 36.) The use of benzene was afterwards 

 advocated by Hoffmann 2 also, who gave it the preference over 

 ether and bisulphide of carbon. Other methods for estimating 

 fixed oils have been described by Munch. 3 Various forms of 

 apparatus that may be used have formed the subjects of .commu- 

 nications from Storch, 4 Wagner, 5 Simon, 6 Tollens, 7 Schulze, 8 

 Tschaplowitz, 9 Medicus, 10 Siewert, 11 Hirschsohn, 12 Keyser, 13 and 

 others. 



The apparatus represented in Fig. 5 is that last devised by 

 Tollens. It consists of a weighed flask, A, holding about 100 cc., 

 to which is tightly fitted, by means of a perforated cork, a glass 

 tube B ; the latter is about 30 mm. in diameter at its upper, and 



1 Pharm. Zeitschr. f. Kussland, i. 44, 1862 ; Anm. Zeitschr. f. anal. Chem. 

 i. 490. 



2 Zeitschr. f. anal. Chemie, vi. 368, 1867. 

 N. Jahrb. f. Pharm. xxv. 8, 1866. 



4 Zeitschr. f. anal. Chemie, vii. 68, 1868. 5 Ibid. ix. 354, 1870. 



6 Ibid. xii. 179, 1873 (Journ. Chem. Soc. xxvii. 293). 



7 Ibid. xiv. 82, 1875, and xvii. 320, 1878. 8 Ibid. xvii. 174, 1878. 

 9 Ibid, xviii. 441, 1879. 10 Ibid. xix. 163, 1880. 



11 Landw. Versuchsst. xxiii. 317, 1879 (Journ. Chem. Soc. xxxvi. 558). 



12 Archiv d. Pharm. [3], x. 486, 1877. 13 Farav. Tidskr. WSO^op, 9 and 19. 



