%\20. 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 CONSTITGENTS ; CH0LESTERIN,,FILICIN, ETC. 



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

 recommended the use of benzene some twenty years ago^ 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. § 3fi.) The use of benzene was afterwards 

 advocated by Hofifmann^ also, who gave it the preference over 

 ether and bisulphide of carbon. Other methods for estimating 

 fixed oils have been described by Miinch.^ Various forms of 

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

 nications from Storch,* Wagner,* Simon,^ ToUens,^ Schulze,^ 

 Tschaplowitz,* Medicus,^'' Siewert,^^ Hirschsohn,^^ Keyser,^^ and 

 others. 



The aj)paratus 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 



^ Pharm. Zeitschr. f. Kussland, i. 44, 1862 ; Anm. Zeitscbr. f. anal. Cbem. 

 i. 490. 



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

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



* Zeitschr. f. anal. Chemie, vii. 68, 1868. ' Ibid, ix, 354, 1870. 



' Ibid. xii. 179, 1873 (Joum. Chem. Soc. xxvli. 293). 

 ' Ibid. xiv. 82, 1875, and xvii. 320, 1878. » Ibid. xvii. 174, 1878. 



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



" Landw. Versuchset. xxiii. 317, 1879 (Joum. Chein. Soo. xxxvi. 558j. 

 " Aichiv d. Pharm. [3], x. 486, 1877. " Farm. Tidakr. 1880, Noa. 9 and 19. 



7—2 



