§ 142. GOLOUR-KEACTIONS. 133 



FroMe's Beagent^ resembles sulphuric acid in its action ; but the 

 colours are purer and make their appearance more rapidly. Very 

 characteristic colours are produced with some oils by sulphuric 

 acid mixed with.-:|th of its volume of a 5 per cent, aqueous solution 

 of ferric chloride. 



The oils should be dissolved in chlorofoi-m, in which the colour- 

 ing, matter is also soluble and thus seen to advantage. 



Oils of pennyroyal, parsley^ coriander, fennel, anise, savin and 

 turpentine cause «o cohwroHon in the chloroform, even after the 

 lapse of some time ; with oils of ledum and peppermint it assumes 

 a red tinge ; with ledum-camphor, and oils of thyme, cajeput, 

 galangal, pepper, cube|}s, copaiba, jumper, violet or bluishrviolef ; 

 with serpyllum, sweet marjoram, rosemary, caraway, dill, nutmeg, 

 cloves, worm-seed, cinnamon, green or bluish-green; with oil of 

 bergamot, etc., olive-green. 



Fuming nitric acid (5 drops to 1 of oil) gives specially charac- 

 teristic colourations with oil's of mace and nutmeg (blood-red), 

 cubebs (green), copaiba (bluish- violet), gaultheria (cherry-red), 

 cinnamon (caxmine), myrrh (reddish-violet), pimento (blood-red), 

 .and pennyroyal (violet). 



Picric acid (0;05 gram, to 5 to 6 drops of oil) is easily dissolved 

 1 y some oils in the cold (caraway, cardamoms, cloves, rosemary, 

 uientha crispa, sweet marjoram, anise, star-anise, dill, valerian, 

 cummin, gaultheria, cinnamon, sweet flag)j by others only on 

 wanning. Some of the solutions deposit Crystals on standing 

 /turpentine, lemon, bergamot, sweet marjoram, mace, dUl, galangal, 

 bitter orange, worm-seed, valerian, cedar-wood, lavender, cajeput, 

 nutmeg, thyme, laurel and sandal-wood) ; others gradually assume 

 characteristic colourations : thus oil of mentha crispa becomes 

 olive-green ; cloves, sweet marjoram, anise, star-anise, nutmeg, 

 ■cinnamon, cummin, amomum and thyme, orange; fennel and 

 myrrh, blood-red ; dill, cascarilla and galangal, brown ; wonn-seed, 

 reddish-brown ; sweet-flag, deep brown ; peppermint, deep grass 

 green. 



Fltickiger^ recommends acting upon a solution of the ethereal - 

 oil in bisulphide of carbon (1 in 15) with sulphuric and nitric acids. 

 With oil of valerian and nitric acid (specific gravity, 1"2) he 

 observed a green colouration of the bisulphide, and red of the atid 



' 1 cc. coho. Bulphurio acid with O'Ol gram inolybdate of soda. 

 » Schweiz. Wochenschr. I. Pharm. 261, 1870. 



