286 Mr. wedgwood’s Experiments 
exp. 6. Water extraSs nothing from it. The riiineral acids, 
with the afiiftance of heat, diflolve about eleven parts out of 
twelve ; but a large quantity of acid is neceffary for this folu- 
tion. The refiduum is greyilh white, full of bright mica- 
ceous particles, with a few fine filaments like thofe of af- 
bellos, which fufFer no change in a moderate red heat. In a 
heat of 1 44 0 , which is 14 0 beyond the fulion of calf iron, it 
ran into a perfect glafs ; but whether this was a vitrification 
of the pure earth itlelf, or of a combination of it with the ar- 
gillaceous matter it was in contact with, the fmallnefs of the 
quantity did not admit of aicertaining. Upon the Hefiian cru- 
cible it formed a black glafs ; what adhered to the thermome- 
ter-piece was brown. 
exp. 7. On boiling with oil of vitriol to drynefs, the bot- 
tom and tides of the mafs became red like colcothar, the mid- 
dle white, the intermediate parts yellow or reddifh yellow, and 
fome greenilh. Thefe appearances were at firfi: attributed to a 
vitriol of iron in different degrees of calcination ; but, on fepa- 
rating fome of the purer white and red parts, the former were 
found to produce in vitrification the fame colour as manganefe 
does, the latter the lame as colcothar ; the other feemed to be 
a mixture of the two. 
exp. 8. A folution of the mineral in nitrous acid was preci- 
pitated, inlfead of common alkali, with Prulfian lixivium, 
which has the property of throwing down from acids iron, 
manganefe, and all metallic bodies, but no one of the earthy 
clafs. When the addition of this lixivium ceafed to make any 
further precipitation, common alkali, added afterwards, had 
alfo no etfebt ; a proof that this mineral contains no earth fo- 
iuble in acids, for that would have remained in the liquor after 
the 
