2$ ACCOUNT of a MINERAL 



fame fubflance fitted to it. The crucible, gradually heatedj 

 was kept in the llrong fire of a fmith's forge for the fpace of 

 half an hour, when it became -very foft. On breaking it after 

 it had cooled, indubitable proofs appeared of the mafs having 

 undergone complete fufion. From being previoufly angulated, 

 it now accommodated itfelf to the Ihape of the crucible, and 

 encruflcd the bottom and fides of it a little way up. 1 he 

 cruft externally, where it flightly adhered to the crucible, was 

 of a dark greyifli colour, internally it had a greenifh Ihade. 

 The matter was light, fpungy and porous like pumice flione, 

 and being carefully colleded weighed only 261 grains. The 

 fpar had therefore loft 77.4 grains, which is at the rate of 23 

 per cent, nearly. 



7. The calcined mafs imbibed water with a hifiing noife and 

 confiderable increafe of temperature, but without fwelling or 

 fplitting like lime, and was foluble in this fluid. On dropping 

 it into diluted muriatic acid, a very flight efFervefcence took 

 place ; but this foon ceafed, and the diffblutioti proceeded ia 

 perfe(!il quiet. The folution had a greenifh caft. 



8. From another mafs, weighing 530.5 grains, I expelled 

 136.5 grains or 25.60 per cent, and ftill it was not altogether 

 non-efTervefcent. I however obtained it once abfolutely cau- 

 ftic or free from carbonic acid, having employed a crucible of 

 Stourbridge clay, which endures a flrong;er heat than the black 

 lead. But I could not in this cafe afcertain the lofs of weight, 

 as part of the mafs had efcaped through a hole it had made for 

 itfelf. 



9. Even by the common blowpipe and candle, a part of the 

 acid may be difengaged. Suppofing that the heat excited by 

 this inftrument, employed in the ufual way, would be very in- 

 adequate to produce the defired effedl, I tried pure air, in the 

 manner I had feen M. Lavoisier ufe it. This mode confifts 

 in direding a flream of oxygenous gas againft ignited charcoal, 



and 



