336 On the Edulcoration of Fish - Oil. 
the gelatinous fluid and bile, gives rise to a further prin- 
ciple of purification than simple edulcoration , or the re- 
moving the fcetor: for the presence of such humours in 
the oil renders it subject to a second putrescence per se , 
supposing the first corrected ; makes it unfit for the pur- 
pose of the woollen manufacture, as the heat through 
which this is in some cases employed causes this matter 
to contract a most disagreeable empyreuma. It also pre- 
vents its burning in lamps, as well from its viscidity as 
from the repugnance which the presence of water gives 
to all oleaginous matter. It is therefore necessary to free 
the oil from this heterogeneous matter; after which it can 
be subject only to the rancid putrescence, or that which is 
proper to oils as such. 
The substances which have been or may be applied to 
the removing or preventing the etfects of putrescence, 
are, acids, alkalies, metallic calces, neutral salts, ethereal 
and essential oils, vinous spirits, water, and air. With 
respect to acids, though they may be applied with effect 
to the removal or prevention of putrefaction in mixed 
animal and vegetable substances, yet they have not the 
same efficacy when employed in the case of oils ; for in a 
small proportion, without the subsequent aid of alkalies, 
they rather increase than diminish the fcetor, and in a 
large proportion they coagulate the oils, and change 
their other properties as well as their consistence. 
Though they might therefore be employed with the as- 
sistance of alkalies, yet, requiring a more expensive and 
complex process, and not being moreover necessary, as 
the same end may be obtained by the use of alkalies only, 
they may be deemed improper for the purification of ani 
mai oils for commercial purposes. Alkaline substances, 
both salts and earths, are the most powerful instruments 
in the edulcoration of oils; but as their action on putrid 
oils, and the method ©f applying them to this end. 
