47 i Experiments on the Fufion of Platina. 



between the platina in this and the former 

 experiment, might probably arife from cavities 

 in the latter, as I have fince frequently found 

 feveral cavities in parcels I have melted. The 

 mafs in experiment fourth was not broken. 



The furfaces of thofe fufions made with fluxes 

 are brighter than thofe melted fer Je^ and for 

 obvious reafons, viz. becaufe the metal in the 

 latter cafe has a more i^nev^n preffure pn its 

 furface. " ---^ 



EXPERI]Vi^')«^T VII. 



Two ounces of platina were melted according to 

 the laft procefs in two hours, with very little lofs 

 of weight. Dr. Pearfon was prefent at this opera- 

 tion, and indeed in mod of thefe experiments fome 

 perfon was prefent with me. 



Dr. Pearfon obferves, " 1 faw Mr. Willi? fufe 

 " pwo ouncj^$ of platina, which he faid he pro- 

 " cured from Mr. Woulfe, who had purified it 

 " by boiling it in the marine acid. The mode 

 " of fufion was by placing the platina, wrapped 

 «' in paper, in the middle af a crucible, of about 

 <' three inches wide, on a bed of charcoal powder. 

 " The charcoal was ground in a coffee-mill, 

 ** the he^t Viras as intenfe as could be given in 

 "his furnace. 



" I put," fays Dr. Pearfon, " five hundred 

 " grains of platina, which had not been purified, 

 " into the middle of finely powdered and fifted 

 " charcoal, in a crucible of about four inches 



" wide. 



