+ 
by thé Vapour of the Fluor Acid. 33 
White Carara marble, in a temperature of 20°, loft, im 
twenty-four hours, -“, of its weight; but ftill the fhining 
furface of its eryftallifed texture was ditinguithable. Weak 
fulphureous acid diffolved one-fourth grain out of forty - 
five; while, of another fragment, of 18 grains, 14 grain 
-was diffolved in the fame time. Black marble fuffered 
no lofs, either in its colour or weight. Agate was not 
attacked. 
Lamellated tranfparent gypfum fell into white powder on 
the furface, after being expofed for a few hours in the appa- 
ratus to the common heat of the ftove, and the Jofs of its 
weight amounted to ,. This powder was not foluble in 
diluted nitrous acid. From this it appears that the vapour 
of the-fluor acid did not deftroy the combination of the cal- 
¢areous earth and the fulphureous acid, but only abftracted 
the gypfum from its water of cryftallifation. 
As the zeolite, among the filiceous ftones, contains the 
greateft quantity of the water of cryttallifation, as the gypfum 
does among the calcareous, I expofed 102 grains of ftriated . 
zeolite at the ftove temperature. In forty-eight hours I 
found its furface friable, and‘its weight only 854 grains; con- 
feyuently 4 lefs, When immerfed in water, and again dried, 
it had inereafed 2'.. It now weighed 88 grains, but did not | 
recover its fplendour. On the tin plate, to which the ftone 
had been faftened with wax, I obferved near the latter a white 
powder, which had the appearance of fomething volatilifed 
from the ftone. I poured over the frothy cake of {parry fluor 
powder and fulphurous -acid a little water, and, after fome 
hours, found the inner fides of the apparatus of tin ‘plate . 
covered with a beautiful filky fubftance, of the brightnefs of 
mother-of-pearl, which was perfedly like that of the zeolite 
jn its natural ftate. But as I afterwards remarked the fame 
appearance of a {plendour like that of mother-of-pearl, after 
expofing other fiones in the fame manner, it is not to be 
aferibed to the zeolite exclufively. On the contrary, I rather 
confider it as an imperfect calcmation of the tin; as, by a 
quicker difengagement of the fluor acid, it, or a mixture of 
it with fulphurous acid, may acquire the’ property of attack- 
yng tin. 
Barytes, of a fibrous texture, when expofed twenty-four 
Vou. Vv. F hor urs 
