122 ETHEREAL OILS. 



Impiire Chloral Hydrate^ (2 di-ops to 1 of oil), resembles the fore- 

 going reagent in the colouration it produces witli jnany oils. It 

 differs, however, in its behaviour to oil of lemon and bergamot, 

 with which it assumes a reddish colom- ; cloves, which turns red 

 on warming ; mace (fine rose-red), pepper (reddish-violet), copaiba 

 (dark-green). Valerian (greenish), cummin (fine green), cinnamon 

 (green, with violet margin), and myrrh (reddish-violet). 



Alcoholic hydrochloric acid varies 'in its action with the amount 

 of acid it contains. A dilute Solution is. to be preferred, as 

 the colourations appear more slowly, but are. purer. Dilute 

 alcoholic hydrochloric acid in the proportion of 15 to 20 drops to 

 1 of oil yields colowless mixtures with oil of turpentine, caraway, 

 coriander, cardamoms (cone, acid, cheiTy-red); cloves,, rosemary 

 (cone, acid, deep cherry-red); yelloio^ mixtures with bergamot 

 (cone, acid, orange to olive-green), inace (cone, acid, reddish- brown), 

 diir(cpnc. acid, cherry-red), bitter orange, cummin (cone, acid, 

 deep violet) ; brownisli-red •mt}x oils of fcascarilla, lavender, sweet 

 marjoram, worm-seed, jumper (cone, acid, red) ; rose to deep red or 

 reddish-violet wit]), oils of cubebs, pepper, copaiba, cedar wood,- cin- 

 namon,, nutmeg, thyme, laurel, sweet-flag and myn-h ; red, tuminri 

 blue, with oil of peppermint. 



Concentrated sulphuric acid (2 or 3 drops to 1 of oil). assumes with 

 most oils a yellow colour, turning brown, and frequently passing 

 finally to a fine red. The latter colouration is observable with 

 oils of caraway, rrientha crispa, sweet marjoram, star-anise, 

 mace, dill, "juniper, cubebs, copaiba, sage, winter-green, lavender, 

 aniomum, cascarilla, nutmeg, thyme, sandal-wood, peppermint, 

 myrrh, and parsley. Oils of . cardamoms, cloves, fennel, anise, 

 cajeput and laui'el produce a violet, cinnamon a greert and blue 

 colouration. 



If a drop of the oil is mixed with J cc. of chloroform and 2 

 drops of cone, sulphuric acid added, similar colours are produced' 

 and imparted to the chloroform. 



' ^ Jehn wa3 the first to observe that this reagent produced a, currant-red 

 oolont with oil of peppermint. Its use is, however, .open to objection, as it is 

 not yet known what impurity causes the colouration, and it is therefore impos- 

 sible to prepare a reagent of constant composition. If 100 cc. of alcohol are 

 saturated .with chlorine, mixed with sulphuric acid (aifter partially separating 

 the hydrochloric acid by evaporation) and the resulting metachloral distilled, a 

 very satisfactory reageilt will be ' obtained, but its activity diminishes on 

 keeping. 



■^ But not if petroleum spirit is used instead of ohlorpfonn. 



