GENERA EUCALYPTUS AND MELALEUCA. 25 



verted into a charred mass, a part of which is dissolved by water, pro- 

 ducing a liquid so dark as to be almost black. 



Nitric acid acts but slowly in the cold ; it gives rise when much 

 concentrated to numerous shades of brown, olive, piirple, violet, and 

 grey ; but when an addition of oil of vitriol is made, or when the nitric 

 acid is employed at a temperature near its boiling point, the action is 

 exceedingly violent ; nitrous acid fumes are given off in great abundance, 

 and the oil is converted into a brown resinous bodv of a pungent odour, 

 hard and brittle, yet becoming plastic like pitch ; soluble in alcohol and 

 ether ; fusing at a moderate heat and inflammable, and possessed of 

 marked acid properties, as it forms coloured salts with the bases, and 

 reddens litmus, in its alcoholic solution. 



Hydrochloric acid does not give rise to very marked results on being 

 simply added to one of these oils ; but the effects produced by this re- 

 agent have not as yet been studied to the extent they deserve. Iodine 

 has been already referred to. What has been said of E. amygdalina, as 

 to its solubility in various liquids, is true of the whole series. 



If a piece of the metal sodium be introduced into one of these volatile 

 oils, an evolution of gas instantly begins upon its surface, and this action 

 is much aided by heat ; it is not under any circumstances as energetic as 

 that caused by the same treatment of some other essential oils, such as 

 oil of cloves. The soda formed is taken up by the oil, giving rise to a 

 dark brown liquid, from which water abstracts the colour, and acquires 

 alkaline properties. Solid potash aided by heat, and a solution of potash 

 in alcohol, act very similarly as far as the change in colour is concerned. 



From what has been said it would appear probable that these volatile 

 fluids must be regarded as oxygenated oils of very similar constitution, 

 holding a camphor, or possibly a liquid carbo-hydrogen in solution, the 

 proportion of which differs in the several varieties. The adoption of 

 such theory helps at least to explain the differences which exist, in bodies 

 otherwise so similar in their boiling points, the separation of solid 

 matter at low temperatures, and above all in the varying purity of colour 

 with which they burn in a lamp supplied with a constant amount of 

 atmospheric air. 



The following summary will be found to give concise information re- 

 specting some of the properties of these oils, and the circumstances 

 under which they were produced. 



E. amygdalina (Dandenong Peppermint). — Gathered in September ; 

 yield from 100 lbs., 60-50 oz. ; specific gravity at 60° F., 0-881 ; boil- 

 ing temperatures, 330° to 370° ; relative illuminating power, the 

 flame of kerosene == 1*000, - 849 ; colour of flame, that of kerosene being 

 white, yellow. This yield is estimated from fresh leaves and branchlets 

 together ; the flame has a tendency to smoke. 



E. amygdalina, from Ballaarat. — Yield from 100 lbs., 31*25 oz. ; 

 specific gravity at 60 p F, 0-907 ; boiling temperatures, 320° to 385° ; 



