§ 124. BEHAVIOUR TO REAGENTS. 105 



almond and castor oil produce no alteration. According to 

 Vidan^ hydrochloric acid containing sugar changes the colour of 

 castor oil to orange-yellow, poppy oil yellowish-brown, ground- 

 nut oil intense yellow, olive oil yellowish-orange, rape oil dark 

 brown, and almond oil yellowish-orange. 



For the use of chloride of antimony as a reagent see Zablu- 

 dowski^ and Walz.' The latter found that on adding a few 

 drops of the reagent, which should be of a syrupy consistence, to 

 2 or 3 cc. of the oil to be examined, olive oil formed a whitish 

 emulsion, gradually turning dark, without any rise in tempera- 

 ture, whilst with cotton-seed oil a considerable amount of heat 

 was evolved, the mixture becoming solid and of a chocolate-brown 

 colour. 



Concentrated solution of chlorinated lime is said to form an 

 emulsion with -8 times its volume of poppy oil, but not with 

 almond oil. 



Caustic, soda oi specific gravity 1 '33, heated to boiling with 4 or 5 

 times its volume of oil, yields a white liquid mixture with castor 

 oil, yellowish-white with sesam6, colza, poppy, and walnut, and 

 yellow with linseed, whilst olive oil and hemp yield respectively 

 brownish and brownish-yellow solid massea* Some oils, such as 

 rape and colza, may be contaminated with sulphur compounds, which 

 may be detected by nitro-prusside of sodium after treatment with 

 caustic soda. 



For the use of the spectroscope in identifying fixed oils see 

 Gilmour,* of the polariscope see Buignet,^ of cohesion figures see 

 Tomlinson,'' Kate Crane,^ and ^Moffat.* 



§ 125. Free Fat-acid. — The presence of free fat acid may be 



' Journ. de Pharm. et de Ohim. xxii. 30, 1875 (Journ. Chem. Soc. xxix. 

 111). Compare also Jahresb. f. Pharm. 288, 1875. The hydrochloric acid 

 and sugar reaction was recommended by Cajnoin as early as 1860. Compare 

 Choulette, 'Observations prat, de Chim. et de Pharm.' Fasc. i. ISO. 



' Pharm. Zeitschr. f. Russland, ii. 233, 1863. 



' Amer. Journ. Pharm. xlvi. 25, 1874. 



* Compare Hager, ' Untersnchungen ' (Giinther Leipsic, 1874), vol. ii. 510. 

 'Pharm. Journ. and Trans. [3], vi. 981, and JahreRb. f. Pharm. 362, 



1876. 



* Journ; de Pharm. et de Chim. xl. 252, 1862 (Amer. Journ. Pharm. xxxiv. 

 140). 



' Pharm. Journ. and Trans. [2], v. 387, 496. 



' Ibid. [3], V. 243, and Jahresb. f. Pharm. 289, 1874. 



' Chem. News, xviii. 473. 



