352 Elements of Mineralogy. 



flour, little clots will be formed, and in fome- 

 thing more than half an hour the whole will 

 gradually grow hot, and at laft burft into a 

 flame, as I have feen feveral times at the 

 houfe of Sir Jofefb Banks. The tempera- 

 ture of the room where the experiment was 

 made was about 50: the heat this ore was 

 expofed to while drying might be about 130. 



1 6. According to Mr. Wedge r woo(T ana- 

 lyfis 100 parts of black wad contain 43 of 

 manganefe, 43 of iron, 4,5 of lead, and 5 

 of mica. 



1 7. To analyfe the abovementioned ores, 

 they fhould be firft roafted to dephlogifticate, 

 the calx of manganefe, and iron if any, then 

 treated with dephlogifticated nitrous acid to 

 diflblve the earths ; the refiduum fhould then 

 be treated with nitrous acid and fugar, by 

 which means a colourlefs folution of manga- 

 nefe will be obtained, which being precipi- 

 tated by aerated mineral alkali, will give a 

 precipitate 100 gr. of which are equivalent 

 to 100 of regulusof manganefe. 



1 8. Many fpecies of iron ore contain man- 

 ganefe. To difcover it, let the iron be dif- 

 folved in fome acid, and precipitated by the 

 PruJJian alkali ; let the folution be poured 

 off, and the precipitate digefted in pure 



water ; 



