399 



The amount of free acid in the water obtained on rectifying the oil of 

 E. cinerea by direct distillation was 2-1 per cent, considered as acetic (see under 

 that species). The barium salt was prepared with the volatile acid similarly with 

 that of E. Smithii. 0-9784 gram, of the barium salt on ignition with sulphuric 

 acid gave 0-8930 gram, barium sulphate, equal to 91-27 per cent. Theory 

 requires 91-37 per cent, barium sulphate, so that in this instance also, it seems 

 probable that acetic acid could only have been present. It will be observed 

 that the amount of free volatile acid in this case was about five times as much 

 as in the distillate from E. Smithii. 



In the water obtained on rectifying the oil of E. phellandra, 0-744 per cent, 

 of free acid was present, calculated as acetic. The barium salt was prepared in 

 the same manner as with the above two species. 0-5265 gram, of the barium 

 salt when ignited with sulphuric acid gave 0-4804 gram, of barium sulphate, 

 equal to 91-25 per cent., so that it is apparent that practically only free acetic 

 acid could have been present as free acid in this oil also. The remainder 

 of the acid distillate was neutralised with soda, and the soda salt crystallised 

 out. Exhibits of pure sodium acetate in each instance were similarly prepared. 



As concordant duplicate results were obtained in each case, it is evident 

 that not more than mere traces of other volatile acids than acetic, could have 

 been present in the oils tested, and as the species chosen were fairly representative 

 of the whole genus, it is assumed that acetic is the free acid in the greater 

 number of freshly distilled Eucalyptus oils. 



The Butyl Ester of Butyric Acid in Eucalyptus 



Oils. 



A LOW boiling ester, with a low refractive index, occurs in some quantity in 

 the oil of E. Perriniana, is characteristic of this species whether growing 

 in Tasmania or New South Wales, and is one of the distinguishing features 

 between this species and E. Gunnii. Considerable work has been done 

 on the oils of these species, distilled from material collected at both localities, 

 and from this data, supported by botanical evidence, it is apparent that these 

 two Eucalypts cannot be considered as identical species. 



This ester is evidently a constant constituent in the oils of the members 

 of a certain class of Eucalypts, although in most cases it occurs but in small 

 amount. It is another instance of the peculiarity, so pronounced with chemical 

 constituents in the genus Eucalyptus, by which is shown a progressive increase 

 throughout a whole series of closely agreeing forms, the maximum being reached 

 in one or more of them. Not only is this the case with the oils, but the various 

 exudations and secretions also show a sequence, often running through the whole 

 group, and this progression is sometimes remarkably complete. 



Butaldehyde is a very common constituent in Eucalyptus oils, and is also 

 one of the constituents which give to unrectified oils of this group a somewhat 

 objectionable odour. The formation of the ester might perhaps be accounted 

 for by a rearrangement in the aldehydic grouping. Normal butyric acid has 

 already been identified as occurring in small quantity in several Eucalyptus oils, 

 this acid probably being derived from the natural hydrolysis of the ester. A 

 corresponding change takes place when the oil of E. Perriniana has been stored 

 for a sufficiently long time, 



