318 
Dr Turner's Experiments, <fyc. 
time, it acted still more sluggishly. Kept for the same time in 
sulphurous acid, sulphuretted hydrogen and annnoniacal gas, it 
had completely lost its energy, for it occasioned no diminution 
of volume when brought in contact with the explosive mixture. 
Spongy platinum was pressed between two pieces of clean 
metal, till it had become a compact leaf of platinum. Its effect 
on a jet of hydrogen was tried at different periods of the pro- 
cess. So long as any of the porous texture remained, it still be- 
came luminous ; but when this was wholly destroyed, it gave no 
light whatever. A very gentle heat still enabled it to become 
luminous, and to inflame the hydrogen. I have repeated with 
success the experiments mentioned by MM. Thenard and Du- 
long, of throwing a jet of hydrogen on a fold of platinum foil, 
and on a coil of the wire. The metal under this form requires 
to be sharply heated for this purpose, to a degree apparently 
beyond that at which mercury boils. 
The lamp without flame, proposed by Sir H. Davy to be ' 
formed with a coil of platinum wire, may be conveniently made 
with spongy platinum. The porous mass need only be sup- 
ported just above, but very close to the wick, by means of a 
small wire ; and when the spirit-lamp is allowed to burn for a 
few seconds, and is then blown out, the metal becomes red, and 
continues so till the alcohol is consumed. By this means a con- 
siderable body of light may be obtained, by which one can read 
small print, or see even the seconds hand of a watch with perfect 
precision. Sir H. Davy proposes to suspend a coil of platinum 
within the safety-lamp, in this expectation, that, should the at- 
mosphere of a mine become at any time so charged with fire- 
damp as to extinguish the lamp itself, the platinum, by main- 
taining a slow combustion, would afford a certain degree of 
light to the miner. Should this be really useful, still greater 
advantage would probably be derived from suspending spongy 
platinum, inclosed in a little wire cage of the same metal within 
the safety-lamp, as the mass of light would then be increased. 
The product of the slow combustion of alcohol by means of 
the porous platinum, is only carbonic acid and water ; I have 
not at least detected either the acetic or any other acid. 
