some new Objects in Chemical Philosophy . 23 
below ignition ; and after combustion, nothing remained but 
minutely divided platina. 
I exposed some of it to heat in a retort, containing oxy- 
gene gas ; there was a diminution of the gas ; and a small 
quantity of moisture condensed on the upper part of the re- 
tort, which proved to be mere water. 
I made two or three experiments, with a view to ascertain 
tlie 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 afterwards distilled in contact with 
platina, there were always from 4 to 6 grains of this powder 
formed ; but I have advanced no further in determining its 
nature, than in ascertaining, that it is platina combined with a 
minute quantity of matter, which affords water by combustion 
in oxygene. 
In the processes on the action of potassium and ammonia, 
in which iron tubes were used, as appears from the experi- 
ments detailed in the last Bakerian lecture, and the appendix, 
there is always a loss of nitrogene, a conversion of a portion 
of potassium into potash, and a production of hydrogene. 
When copper tubes are employed, the hydrogene bears a 
smaller proportion to the nitrogene ; and more potassium is 
revived. 
In these experiments, in which platina has been used, 
there is little or no loss of potassium or nitrogene ; but a loss 
smaller, or greater of hydrogene. 
It will be asked, on what do these circumstances depend ? 
Do the affinity of certain metals for potassium, prevent it from 
gaining oxygene from ammonia, and do platina and copper 
