349 
of Kapeseed Oil . 
phuric acid : it is this matter which colours the oil, and 
prevents it from burning with facility. Three very dis- 
tinct strata, then, are established, as is here seen : the up- 
per one is oil ; the second is aqueous, and contains a little 
sulphuric acid ; and the third is carbonaceous. The oil 
which forms the upper stratum, after these eight days of 
rest, is far from being limpid : twenty days, in my opi- 
nion, would be necessary for it to purify itself merely by 
repose ; but by filtration it may be immediately obtained 
perfectly clear and transparent. For this purpose, pound- 
ed charcoal, and a piece of linen or cotton cloth, may be 
employed : the two last substances are preferable to any 
other. The same cloth will serve several times, only it 
must be carefully cleaned. 
By following this process with attention, you may ob- 
tain oil which has much less colour, odour, and taste, than 
that commonly used ; which will burn with the greatest 
facility, and without any residuum ; and which is equal 
to the purest oil sold in the shops, &c. The loss is very 
inconsiderable. 
If you are desirous of obtaining it still purer, it may 
be exposed again to the same treatment ; but, in that case, 
for one hundred parts of oil, one hundredth part of con- 
centrated sulphuric acid will be sufficient. The sul- 
phuric acid will not form in oil which has been once pu- 
rified a blackish precipitate ; on the contrary, it produces 
a very scanty precipitate, of a grayish-white colour. 
This precipitate is more difficult to be separated than the 
former. 
When the oil has been treated with two hundredth 
parts of sulphuric acid, if it be suffered to digest for 
twenty-four hours with the fourth of its weight of chalk 
or carbonate of lime, or of argil, you will obtain it al- 
most as clear as water. Lime, however, cannot be em- 
ployed with advantage, as it would occasion too much 
