Op the Edulcoration of Fl/h-Oil. 107 



manufaolure, as the heat through v^hich this is in fome cafes 

 employed caufes this matter to contrail, a moft difagreeable 

 Cmpyreuma. It alfo prevents its burning in lamps, as well 

 from its viicidity as from the rcjiugnance which the prefencd 

 of water siives to all oleaginous matter. It is therefore ne- 

 eeflary to free the oil from this heterogeneous matter; attef 

 which it can he fubjecl only to the rancid piitrefcence, of 

 that which is proper to oils as fiich. 



The iubdances which have been or maV be applied to the 

 removing or preventing the eftefts of pntrefcence, are, acids, 

 alkalies, metallic calces, neutral falls, ethereal and eO'cntial 

 oils, vinous fpirits, water, and air. With refpe(:vt to acid?, 

 though they may he applied with eflTcft to the removal ot 

 prevention of putrefaction in mixed animal and vegetable fub* 

 fiances, yet they have not the lame efficacy when employed 

 in the cafe of oils ; for in a fmnll proportion, without the fiib^ 

 fequentaid of alkalies, they rather increaic than diminifli the 

 fcetor, and in a lai-ge proportion they coagulate the oils, and 

 change their other properties as well as their oonfilUnce. 

 Though they might therefore be employed with the aflift- 

 ance of alkalies, yet, requiring a more expenfive and Complex 

 procefs, and not being moreover necellary, as the fame end 

 may be obtained by the nfe of alkalies only, they may be 

 deemed improper for the purification of animal oils for com- 

 mercial purpofes. Alkaline fubltances, both falts and earths, 

 are the moft powerful inltruments in the edulcoration of oils; 

 but as their action on putrid oils, and the method of apply- 

 ing them to this end, are not the fame in both, it is proper 

 to confider them ditlinftlv. 



Of alkaline falls it is the fixed kind only which are propet 

 to be ufed for the edulcoration of oils. Fixed alkaline falts, 

 jn a diffolved Hate, being commixed with putrefvin* animal 

 (ubftanccs, appear to combine with the putrid matter, and, 

 mixing with Ibme of the principles, form inftantlv volatile 

 alkaline i'alts. On the lefs putrid they feem to a6f, afttr thcif 

 combination, by an acceleration of the putrefcent adion, till 

 they attain the degree which produces volatile falts. This 

 is evident by the fenfil)le putrid ferment and fmell which 

 appear after their connnixture; but wliich gradually abatinrr, 

 the oil is rendered fweeter, much lighter coloiJred, and 

 thinner. 



Their great ufe in tl.e edulcoration of fifli-oil arifes there- 

 fore from their converting huh parts of iho c^latinous fluid 

 and bile as are highly putrefied iulianlly into volatile falts, 

 ^nd caufing a rapid putrefaction of the other parts ; by whicti 

 pieans the oil it; freed from tliem by their diiiipatiun. They 

 V do 



