on the Verra panderata, &ey. Kee ASE 
oehe ae, ‘may be freed from this powder cither by diftilla-. 
tion in glais veflels, which i Is a tedious. and dangerous procefs, 
or by the affufion.of water; and, after bie powder has fubfided, 
a gentle evaporation. w ill drive 8 mott ‘of the, fuperfluous 
RAE oth. 2 | 
. Nirrous ACID > may he freed from stale eee marine, acids, 
s folution of filver in the acid of nitre,. as is daily practifed 
but the MARINE ACID has not, to my knowledge, been puri- 
fied by any. other method than the laborious one of re-diftilling 
it from common falt. Ti 1s generally mixed with, vitriolic on 
~and often in large proportion. There is no temptation, and 
{earcely an opportunity, for it to be contaminated by nitrous 
acid. From the-vitriolic a acid then it may be readily purified by 
the addition of terra ponderofa cauftica diffolved in water, or 
by, the terra oe falita. If the ae be ufed, a {mall 
Ste Eun by dilticn write ete: ‘and oe Fea Ww rae ‘Drs Bite loves gave 
me, being the refiduum of vitriolic acid dittilled to drynefs ina HAs elafs retort. 
ift, Repédted boiling i im water, reduced 62 grains to 2 grains. + 
.* adly, This! folution,. by’ gentle’ evaporation, afforded 5, grains of cryftals, as 
hard and as taftelefs as felenite. 
3dly, To thefe cryftals, re-diffolved in water, mild fof Lally was added, and 
‘gq white powder’precipitated. 22); /. ; iat 
, '4thly, This powder, after expofure: to a a pretty: insu ia was thrown inte 
water ; part of it diffolved, and the water got Tee tate and other properties of 
rh sZ 
Sime- water. 
sthly, The infoluble part (1.) fuffered no change by boiling in nitrous acid ¢ 
ene-half of it mixed with borax, and expofed to the blow-pipe upon gharcoal, 
vitrified ; ; the other half, ‘mixed with borax and charcoal-duft, likewife vitrified. 
py TORERESEONS: It appears, then, that the greater part of this fabiaace was 
eal vite or felenite ; ‘the remainder a vitrifidble earth. 
“I had before found, that the terra ponderofa vitriolata, -or heavy gypfum, would 
diffelve in concentrated vitriolic acid 5 but always. feparated ina powdery form 
upon the affufion of water; and now it appears, that calx vitriolata, or felenite, 
does the fame. : 
ki : portion 

