May as, 1914 
Aroma of Hops 
153 
It is very probable that esters of the higher acids, as heptoic, octoic, 
and nonoic, would boil at higher temperatures than myrcenyl acetate. 
This would necessitate the concentration of the esters in fractions, as 
shown above. Earlier fractions would also contain some esters, as 
would later fractions, since the association of lower and higher boiling 
compounds with the esters would modify their boiling points. In order 
to show that the esters constitute no small proportion of the oil, curves 
of fractionation were made of the original oil (containing esters) and the 
same oil after saponification of the esters (fig. 14). 
The curves show directly opposite courses from each other between 
the temperatures 170° and 260° C. It was between these temperatures 
that the large proportion of the esters of the original oil distilled over. 
It can therefore be readily perceived that a destruction of these esters 
by saponification and the consequent removal of the high-boiling acid 
portion of the esters would tend to flatten the curve of fractionation 
between these respective points. 
The presence of the esters of myrcenol in the oil of hops is not sur¬ 
prising when it is known that the hydrocarbon myrcene, found in the 
low-boiling fractions, can be readily changed to myrcenol by the action 
of glacial acetic acid and dilute sulphuric acid. Myrcene bears the same 
relation to the alcohol myrcenol that camphor does to isobomeol and 
pinene or that dipentene bears to terpineol. , It is very likely that the 
hydrocarbon myrcene is partly changed to myrcenol by hydration during 
the formation of the essential oil in the plant, the myrcenol in turn being 
esterified by the organic acids present. 
