TUR1FICATI0N OF FJSH-OIL. *J 



the fir ft corrected ; makes it unfit for the purpofe of the woollen 

 manufacture, as the heat through which this is in fome cafes 

 employed, caufes this matter to contract a moft difagreeable 

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

 from its vifcidity as from the repugnance which the prefence 

 of water gives to all oleaginous matter. It is therefore neeef- 

 iary to free the oil from this heterogeneous matter; after 

 which it can be fubject only to the rancid putrefcence, or 

 that which is proper to oils as fuch. 



The fubftances which have been or may be applied to the Enumeration of 

 removing or preventing the effects of putrefcence, are, acids, p ° r |^g ^^ 

 alkalies, metallic calces, neutral falts, ethereal and eflential Acids, alkalies, 

 oils, vinous fpirits, water, and air. With refpeft to acids, J*jJ e \£%f 

 though they may be applied with effect to the removal or alcohol, waterj 

 prevention of putrefaction in mixed animal and vegetable 3 ' 1 ' 

 fubftances, yet they have not the fame efficacy when emr eligible, 

 ployed in the cafe of oils j for in a fmall proportion, without 

 the fubfequent aid of alkalies, they rather increafe than 

 diminifh the foetor, and in a large proportion they CQagulatp 

 the oils, and change their other properties as well as their con- 

 fidence. Though they might therefore be employed with 

 the affiftance of alkalies, yet requiring a more expenfive and 

 complex procefs, and not being moreover necelfary, as the 

 fame end may be obtained by the ufe of alkalies only, they 

 may be deemed improper for the purification of animal oils 

 for commercial purpofes. Alkaline fubftances, both falts but alkalies are 

 and earths, are the m oft powerful inftruments in the edul- tefl > 

 coration of oils ; but as their action on putrid oils, and the 

 method of applying them to this end, are not the fame in. 

 both, it is proper to confider them diftin&ly. 



Of alkaline falts it is the fixed kind only which are proper Fixed alkaline 

 to be ufed for the edulcoration of oils. Fixed alkaline falts, ca ^onates in- 

 jn a diflblved ftate, being commixed with putrefying animal proce f s j C P ° 

 fubftapcps, appear to combine with putrid matter, and mixing 

 with fome of the principles, form inftantly volatile alkaline 

 falts. On the lefs putrid they feem to a&, after their com- 

 bination, by an acceleration of the putrefcent action, till 

 they attain the degree which produces volatile falts. This is 

 evident by the fenfible pijtrid ferment and fmell which appear 

 after their commixture ; but which gradually abating, the qil 

 is rendered fweeter, much lighter-coloured and thinner. 



