36 



The cineol in the oil of this species is always small in .amount, averaging 

 probably between 5 and 8 per cent. It is impossible to determine this small 

 amount accurately by the phosphoric acid method, or by any other known method 

 besides absorption with 50 per cent, resorcinol. Statements have been made 

 that the resorcinol method indicates the presence of a much larger quantity of 

 cineol than the oil actually contains, an - d that is so, if the results of the direct 

 absorption be taken without correction. On rectifying the oil so as to separate 

 the constituents boiling between 170-190 C., a considerable quantity of pi peri- 

 tone comes over, and is absorbed by the resorcinol at the same time as the 

 cineol. The piperitone can, however, be readily estimated by a ketone deter- 

 mination, using the normal sodium sulphite method, and the amount so found 

 when subtracted from the total absorbed, will give the cineol. 



An actual determination will make this clear. A sample of freshly-distilled 

 oil of E. dives was forwarded to us by Mr. A. J. Bedwell, in November, 1919; 

 it was typical of the oil of this species. The crude oil had : 



Specific gravity at 15 C = 0-8828. 



Optical rotation a D ... ... ... ... -68-0 



Refractive index at 20 ... ... ... ... = 1-4769. 



Soluble in i volume 80 per cent, alcohol. 



Ketone determination ... ... ... ... =29 per cent. 



65 per cent, distilled below 190 C. (corr.). This had : 



Specific gravity at 15 ... ... ... .-.. = 0-8592. 



Rotation a D .. ... ... ... ... ... - 77'2- 



Refractive index.,at 20 ... ... ... ... = 1-4734. 



Resorcinol absorption = 22-5 per cent. 



Ketone determination ... ... ... ... = 10-0 per cent. 



Cineol after correction ... ... ... ... = 12-5 per cent. 



When calculated for the original oil the result was 8 per cent, of cineol. 

 The portion boiling above 190 C. (35 per cent, of original oil), had 

 specific gravity at 15 C. = 0-9335; rotation a D - - 38-2; refractive index at 

 20 C. = : i'4855 ; and ketone estimation 75 per cent. 



The non-ketone portion of the original oil had specific gravity at 15 C. 

 = 0-8633; rotation D -- 70-2; refractive index at 20 = 1-4746; saponification 

 number = 15-93, and after acetylation = 38-35, which calculated for a C IO H I8 O 

 alcohol gives 6-3 per cent. This alcohol is probably piperitol, largely, as in the 

 oil of E. radiata. 



166. Eucalyptus radiata. 



(Sieb., in DC. Pro;!., iii, 218.) 

 White-top Peppermint or River White Gum. 



Systematic. A fairly tall tree. It has a hard, black bark on the lower 

 part of the trunk, but smooth on the upper portion of the tree. Abnormal leaves 

 thin, sessile, or almost perfoliate, much resembling those of the " Messmate " 

 E. phellandra, opposite, narrow, about 3 to 4 inches long, marginal vein slightly 

 removed from the edges. Normal leaves lanceolate, narrow, generally about 



