ON THE OXIDES OF LEAD. g37 



5. Sixty-three grains of the fait, partly in fcales and partly The oxide of 

 In needles, were fufed with carbonate of potalli in a Wedge- not"diirent' 

 wood crucible. By folution and filtration a fiedi-coiou red from the yellow, 

 powder was obtained, which was a mixture of oxide of lead 



and filica. It weighed 53 grains ; but a portion which I could 

 not eftimate adhered to the crucible. The filica was obvioufly 

 abraded from that veflfel. Thirty grains of this powder di- 

 gefted in nitric acid, left 3f grains of filica; of courfe, 26f 

 were ditTolved. The folution yielded 39f grains of nitrate o( 

 lead. Now 39| of nitrate contain 27 grains of yellow oxide, 

 or almoft the very quantity diflblved. The oxide obtained by 

 this experiment, then, was the yellow ; of courfe, it coincides 

 exadlly with the preceding ores. 



Proufl's fait, then, does not appear to contain a different 

 oxide from common nitrate; but its new properties were 

 owing to the different proportion of its acid. It is completely 

 neutralized, whereas common nitrate contains an excefs of 

 acid, and is, in fa6l, a fuper-nitrate. But if this conclufion 

 be well founded, Proufl's nitrate may be formed by expofing 

 common nitrate to a heat fufficient to expel the excefs of » 



acid. It was requifite to verify this prefumption by experi- 

 ment. 



6. One hundred grains of nitrate of lead (dried in 300^)prou(l's fait 

 were expofed to a graduated heat in a flafk. Fumes of nitrous made by ab- 

 acid feparated in abundance, and the fait loft five j9er cew^ ftgad of adding' 

 of its weight. On increafing the temperature the fait melted '"'J- 



into a tranfparent glafs of a very pale yellow colour. The 

 weight of the mafs was now reduced to 85 grains. Hence it 

 was compofed of 68.5 oxide and 16.5 acid, or, per cent, of 



80 oxide, 



20 acid. 



100. 

 On pouring water into the flafk and digefiing, I obtained a 

 yellow folution fimilar to that formed by boiling lead in nitrate 

 of lead, but not fo deep. A yellow powder refufed to dif- 

 folve ; it confifted chiefly of the portion of fall at (he bottom 

 of the flafli, which had been expofed to a higher temperature. 

 It was taftelefs, and not unlike fub-muriate of lead. When 

 heated to rednefs it melted into a yellow glafs, and loft 14- per 

 salt. It was therefore compofed of 



2 '86 



