24 ESSENTIAL OILS FROM THE 



plants of this genus, must yet be regarded as relatively unproductive 

 material. From 100 lbs. of the fresh green material four ounces of a 

 pale yellow oil are obtained. In smell it is like curvifolia ; its taste is 

 very diffusible and pungent. Its specific gravity is - 925. 



This "plant has been found hitherto only in the vicinity of Lake 

 Hindmarsh, and the Tatiara country, and the River Wimmera. It is a 

 desert species. 



Melaleuca uncinata. — This plant is essentially a desert species ; it 

 ranges from Victoria across the continent to Western Australia, and 

 forms a slender and graceful shrub. The colour of its essential oil is 

 green, being in this respect exactly similar to cajeput, but in taste it 

 resembles more the Eucalypti. In smell it is like M. ericifolia, with an 

 addition of peppermint. The yield from 100 lbs. of the plant is approx- 

 imately 1 ounce 6 drachms. 



Melaleuca genistifolia. — 100 lbs. of this shrub yield 1 ounce 2 drachms 

 of a pale greenish yellow oil, mild in odour and taste ; but both cha- 

 racteristic of the tea-tree oils. The quantity submitted for investigation 

 was not sufficiently large to admit of determining its specific gravity and 

 boiling points. The M. genistifolia accompanies the M. linarifolia, 

 but is rare in Victoria. 



Melaleuca squarrosa. — This oil is also coloured green. It resembles 

 that of uncinata and ericifolia, but its taste is disagreeable ; and, while it 

 retains in this respect the character peculiar to the tea-tree oils, its 

 flavour is somewhat vapid. The yield from M. squarrosa is small, being 

 only 5 drachms from 100 lbs. of the shrub. 



This is one of the most common of the tea-tree shrubs, being fre- 

 quently found with ericifolia in tea-tree swamps, though, unlike it, it 

 assumes in deep forest dells the dimensions of a large tree. 



Before passing from the consideration of the essential oils of this 

 class, it is desirable to make some observations bearing upon their tech- 

 nical impoitance and general characteristics. 



The similarity in the properties of the oils which have been described 

 is so great, that the investigations made respecting them have failed to 

 establish individual peculiarities, sufficiently marked to enable the che- 

 mist to distinguish with certainty between them, and tell by the exami- 

 nrtion of a sample the source from which it was obtained. In a practical 

 point of view this want will be little felt, as for the manufacture of var- 

 nishes, the dissolving of india-rubber, or for illuminating purposes, they 

 are almost equally valuable. The behaviour of these substances when 

 subjected to the action of re-agents may be shortly stated as follows : 



With sulphuric acid at ordinary temperatures a gradual darkening 

 in colour is perceptible, the tint varying slightly according to the oil 

 operated upon, but the final result is in all cases a deep brown- 

 When heat is employed, these changes are rapidly brought about ; the 

 acid is decomposed, giving rise to sulphurous acid gas, and the oil is con- 



