GIXGEE. 101 



270^ C. A little passes over between 270^ and 300^, but 

 evidently accompanied by decomposition products, and a trans- 

 parent brown tenacious semi-solid residue remains in the flask. 

 The English oil gave : — 



Boiling below* ... 150° C. about 5 per cent, 



between 



liesidue in retort . . . 



100 

 From the " Foreic^n " oil was obtained : — 



Boiling below 210° C. about 17 per cent. 



between ... 210^-250° C. „ 15 „ „ 



250^-270^0. „ 45 „ ;, 



270^-310° C. „ 10 „ ., 



Eesidue in retort ... ... ... ... 13 „ „ 



100 

 The lower boiling products retained the ginger aroma (perceptible 

 when diluted with spirit) and were much more soluble in rectified 

 spirit than the higher fractions." Further than this, Thresh's 

 researches do not appear to have led to any definite conclusion as 

 to the constitution of the oil. 



Oil of ginger is yellow in colour. Its odour is intensely that 

 of the root (the oil of Jamaica root being the most fragrant), but 

 it has not the pungent burning taste of ginger ; this taste is due 

 to gingerol, the active pungent principal of the root. Probably it 

 is for this reason that the spirituous extract of the rhizome is 

 preferred by the liqueur makers, as it contains both the essential 

 oil and the pungent principle. 



GIngerol. The investigations of Thresh show that this body 

 exists in the dried rhizomes to the extent of from 0*600 to 1*450 

 per cent. He eliminated it in the form of a viscid fluid of about the 

 consistency of treacle, of a pale straw colour, entirely devoid of 

 odour, and of an extremely pungent and slightly bitter taste. It 



* All boiling points are corrected for portion of thermometer tube not 

 immersed in vapour. 



