Metallic Oxydes and Earths. 211 
on the hands, they inftantly fhrivelled the fkin, 
and were either abforbed, or foon dried up. Two 
phials of Nos. 1 and 2 being left expofed to the 
action of air and light, for fome months, were not 
in the leaft changed. 
As’ it was evident, that a confiderable portion of 
arfenic was diffolved in all the foregoing experi- 
ments, I wifhed to fee, if it could be precipitated ; and 
-at the fame time the oils be left pure, and deprived 
of colour; though with no great hopes of fuccefs, 
from the known property of the mineral acids to 
render oils thick and difcoloured. 
5- Part of No. 1 being poured into a phial, 
three or four drops of ftrong vitriolic acid were 
added. ‘The arfenic immediately precipitated, 
leaving the oil as pure and colourlefs as before. 
6. The fame quantity of vitriolic acid being 
added to Nos. 2, 3, and 4, the arfenic was in like 
manner precipitated. No. 2 feemed even clearer 
than before the addition of acid. 
7. Nitrous acid being added, in the fame pro- 
_ portion with the vitriolic, the colour of all the oils 
was inftantly changed toa dark brown, except the 
Sperma Ceti oil, which was not much affected ; the 
train and lin-feed oils fuffering the greateft change. 
In all of them a flight effervefcence took place. 
8. Marine acid occafioned a precipitation, which 
foon rediffolved, in all of them. 
g- Both the fixed alcalies iminediately coagulated 
the oils, the water, in which the folution of alcali 
Dde was 
