feXPERIMENTS ON THE METALS FROM THE FIXED ALKALIS. 327 



The 8 cubical inches of gas contained scarcely f of a Results, 

 cubical inch of ammonia ; and the unabsorbable part de- 

 tonated with oxigen, in the proportion of 11 to 6, gave a 

 residuum of 7*5. — The barometer was at 30*2 in., thermo- 

 meter at 52° Fahrenheit. Dr. Pearson, Mr. Allen, and 

 Mr. Pepys were present during the whole of these opera- 

 tions, and kindly assisted in the progress of them. 



Now 6-78 — *4 of ammonia = 6*38, and this quantity of Deductions 

 gas, decomposed by electricity, would afford 114 of per- 

 manent gas, consisting of 2*9 nitrogen, and 8*5 hidrogen. 

 But there are produced in this experiment, of hidrogen, 

 2*48 in the first operation, and 4*28 in the second ; and, 

 considering the nitrogen in the permanent gas as 3*32, 08 

 must be subtracted from the common air; which would give 

 2*52 for the nitrogen generated: and to these must be 

 added the quantity of hidrogen and nitrogen in the tubes 

 and adaptors. 



The quantity of potassium regenerated was sufficient to 

 produce 2*9 cubical inches of hidrogen. 



In all experiments of this kind a considerable quantity of Black matter 

 black matter separated, during the time the potassium in 

 the tube was made to act upon water. 



This substance was examined. It was in the state of a This examined. 

 fine powder. It had the lustre of plumbago, it was a con- 

 ductor of electricity. When it was heated, it took fire at 

 a temperature below ignition ; and after combustion, no- 

 thing remained but minutely divided platina. I exposed 

 some of it to heat in a retort, containing oxigen gas ; there 

 was a diminution of the gas, and a small quantity of mois- 

 ture condensed on the upper part of the retort, which 

 proved to be mere water, 



I made two or three experiments, with a view to ascertain 

 the quantity of this substance formed, and to determine 

 more fully its nature. I found, that in the process in 

 which from 3 to 4 grains of potassium were made to act 

 upon ammonia in a vessel of platina, and afterward dis- 

 tilled in contact with platina, there were always from 4 to 

 6 grains of thjs powder formed; but I have advanced no 

 farther in determining its nature, than in ascertaining, that A compound of 

 it is platina combined with a minute quantity of matter, ft tina ^{l* 

 vuicn affords water bv combustion in oxigen. * rogen "' 



In 



