1817.) On the Decomposition of the Earths. 197 
University ; but as it has been confirmed by your high authority, * 
the evidence will be deemed sufficient ‘* by all who are willing to 
give a peaceful entrance to truth.” I have sometimes altered the nature 
of the gases, and have often tried the effect of varying the propor- 
tion between them ; but the greatest degree of heat has always been 
“produced, if the gases be perfectly pure, by mixing them exactly 
in the proportion for forming water. A greater excess of hydrogen, 
as it renders the mixtare less explosive, always proportionally dimi- 
nishes the heat. With Professor Cumming, 1 made trial of the 
carburetted hydrogen gas ina state of mixture with oxygen. Its 
combustion was characterized by a flame of a sapphire-blue colour ; 
but the heat was barely sufficient for the combustion of zon wire. 
Platinum was not melted by it. The Professor himself had pre- 
viously tried a mixture of the super-carburetted hydrogen, or ole- 
frant gas, with oxygen; but found the heat also defective, In the 
following experiments, the gases were mixed according to the pro- 
portions originally suggested by experiments for the formation of 
water, and by the phenomena, attending its decomposition, which 
I had myself witnessed during a long residence upon Mount 
Vesuvius, 
Continuation of the Experiments. 
1. Muriate of Barytes.—As this substance has been supposed by 
Sir H. Davy to be a compound of the metal of barytes with chlorine 
in the proportion of 0°66 of the metal, to 0°34 of chlorine, I 
wished to effect the volatilization of the chlorine, for the develope- 
ment of the metal. ‘The experiment succeeded ; but it often fails; 
owing to the volatilization of the minute globules of metal in the 
moment of their revival. The plan I adopted was, to place the 
muriate first upon charcoal, and after its ebullition ceases to collect 
the dry mass, together with some of the charcoal, and again expose 
the whole to the ignited gas in a charcoal crucible. In this manner 
I observed the brilliant globules of the metal dispersed upon the 
surface of the charcoal, as they were exhibited to Mr. Holme and 
to me in a former experiment with the nitrate of barytes; and as 
he has since described their appearance ;f but in this instance they 
were so exceedingly minute that [ could not succeed in my endea- 
vours to place them, as before, in naftha. 
1 succeeded however in obtaining very large globules of the 
metal of darytes in the highest state of metallic lustre of which 
any metal is capable, and which for a long time were preserved 
in naftha, and exhibited to Professor Cumming, to Mr. Holme, 
and to other chemists of this University, by a different process, 
1 mixed the two gases in the proportion of three parts of hy- 
drogen, by bulk, to one part of oxygen. ‘The heat in this case 
is less intense, but the deoxidating power may perhaps be 
greater. 1 exposed some pure barytes to the flame of this gaseous 
* See Annals, ix, T. 
+ See Mr, Holme’s observations upon the reduction of barytes to the metallic 
#late, Annals, viii, 471, B+ 
