§ 122. ULAIDIN, TEST FOB, ETC. 101 



5 to 7 at its lower extremity ; the former communicates by means 

 of perforated corks with the condenser D. A glass tube, JE, about 

 20 mm, in diameter, is supported upon a bent glass rod, "F, in such 

 a manner that, the condensed vapour from C drops directly into 

 it. In this tube, E, the substance to be examined is carefully 

 packed ; a piece of filtering-papet is then tied over the lower end, 

 and a small circular filter laid upon the surface of the packed 

 substance. During the extraction the heat is so regulated that 

 the material is constantly covered by a layer of ether 1 to 2 cm. 

 thick. 



§ 121. ResirdficaHon. — The rapidity with which an oil resinifies 

 may be ascertained by exposing it to the air in thin layers and 

 noting the daily increase in weight. Parallel experiments should 

 be made witli almond and linseed oil under precisely similar con- 

 ditions. The oil used .should be quite free from any trace of 

 petroleum spirit. 



§ 122. Elaidin Ted. — This test ^ 12) consists in passing nitrous 

 acid into a few cc. of the oil and observing the length of time that 

 elapses before solidification takes place. Another method is to 

 introduce copper turnings or a little mercury, together with nitric 

 acid, into a test-tube, and pour a few cc. of the oil upon the 

 mixture. The colour also ,of the elaidin produced may be 

 characteristic of the oil under examination. 



Using 5- grams of nitric acid, sp. gr. 1-4, and 1 gram of 

 mercury to 10 grams of oil, Massiei observed the following 

 reactions ; 



On agitating the oil with the nitric acid alone for two minutes 

 and allowing the liquids to separate, the following colourations 

 were observed : abnond, hazelnut, suniiower-seed oil, colourless or 

 sliglttly greenish ; olive oil, greenish, while or slightly yellowish-green, 

 or distinctly green; ground-nut oil and poppy-seed oil, reddish; 

 castor and sesaiu^ oil, yellowish or yellowish-orange; oil of white 

 mustard, apricot, walnut, camelina, beech, rape and linseed oil, 

 cherry-red or reddish-orange; oil of black mustard, cotton and 

 hemp-seed oil, brown or hrowaish-red. 



The acid was coloured yellowish by olive oil (occasionally), 

 saffron-yellow by sesam6, light brown with cotton, and slightly 

 reddish or greenish by hemp oil. 



After the addition and solution of the mercury, the mixture is 

 'Journal de Pharm. et de Chim. [4], xii. 13, 1869. 



