PURIUCATION OF OIL. 151 



However, as the art of purifying oils ought to be known 

 hy Jhofe who manufacture them, the pfoceffes, which are 

 confidered the moft economical and fimplc, Oiall be here 

 mentioned ; by which information they will be able to obtahi 

 that profit which thofe now make who tbllow this fpecies of 

 induftry after them. 



The procefs for the purification of oil by fulphuric acid, Procefs by fuj- 

 which follows, is little different from ihat publithed by ^^^^"^'jj''''* ''*'■ 

 Thenard. 



To one hundred parts of rape oil one part of fulphuric acid Sulphuric acid 



IS to be added, diluted with fix times ils weight of water; ^ the olT- ''uS* 



the mixture lliould be ftrongly agitated, and as foon as this is mixture I'trongly 



completely finiQied, it is left ftill till the oil becomes clear ; ^'J'^^'^ f^ 

 , . . ^ , 'etc to fettle. 



when It js perfeftly clear the purification is effeded. 



There remains at the bottom of the vefi'el an acid liquor 



foraewhat coloured : the oil is to be feparated from the fedi- ^^^ «'• f^pa- 

 , . , , . , ... • J 1 '^^'^^^ f'oi" the 



ment; and in order to be certain that no acid is retained by fedi«ieni- pow- 



the oil, fome ounces of powdered chalk is to be added ; the '^^red chalk 



mixture fhould then be fliaken, and the oil again left ^uie.t^ j^„^'jfj^j"^^^|^j. 



to fettle. to fettle. 



The a<5lIon of the fulphuric acid in this procefs confifts in 



deprivirrg the oil of all its humidity, although it is ilfelf mixed 



with water, and in feparating from it a mucofo-exlradive The acid in this 



fubftance, the prefence of which diminilhes the energy of the fhe'^iucXex! 



combuftion of the oil, covers the wick with charcoal, and tiaflive matter 



produces much fmoke : It is then on the abftradion of thefe "°|" the "il, 

 . . . ..... . which injures it9 



principles foreign to the oil, that its quality ol giving a good combuftioR, 



light depends. 



Another Method, 



The next procefs to be defcribed has been followed by fome Procefs by flour 

 manufacturers, who have had good fuccefs with it. ^"*^ water. 



To one hundred parts of rape-feed oil ten parts of water Flour and water 

 are to be put, to which one part of wheaten flour has been ^J^^^j^'^^'j^'^J^jJ''' 

 added J the mixture is to be well agitated, and (hen to be agitated, and 



heated until all the water added has been evaporated, or, ^^^^'^.'^ *'^'/ J^- 

 1 -1 , •. 1 /• I 1 parationof the 



more properly, until the oil has cealed to have any union contained mat- 

 wiih the fttbftances which it held in fufpenfion : In this fiate^ers ^nfues ; in 

 it becomes purified; and at the end of twenty-four hours it^jjij j^is ^lear, 

 is very clear, and does not differ at all in quality from that 

 prepared by fulphuric acid. 



In 



