IProf. Doeberemer's recent Discovery , to Eudiometry . 101 
heat, I obtained the platinum in a very altered condition ; for it 
was firm, and had contracted to at least one-half of its former 
volume* For these reasons, I had recourse to the balls pro- 
posed by Professor Doebereiner. I mixed together spongy pla- 
tinum and pipe-clay, in different proportions, and, by the addi- 
tion of a little water, made a set of balls, about the size of a pea. 
As the activity of spongy platinum is in some way connected 
with its porous texture, X endeavoured to bring the balls as 
nearly into a similar condition as possible. With this intention, 
a little powdered sal-ammoniac was mixed with the platinum and 
pipe-clay, and when the balls had become dry, they were cau- 
tiously ignited at the flame of a spirit-lamp. The sal-ammoniac 
escaping from all parts of the ball, gave it a degree of porosity 
which was very favourable to its action. In this way twelve 
different balls were formed, the exact composition of which 
I subjoin. 
Platina. Pipe-clay. 
jSTo. 1. consists of 5 grains, 1 grain* 
2 . 
4 
1 
3. 
3 
1 
4. 
4 
2 
■5. 
% 
4 
6. 
2 
4 
7. 
2 
$ 
8. 
1 
5 
Silica* 
9. 
0-25 
0*5 
1.25 
10. 
0-5 
15 
3 
11 . 
0-25 
2.0 
1 
12. 
0-25 
2.0 
1*5 
Siliceous earth was added to the four last, since the pipe-clay 
alone made the mass too tenacious. I found that any of the four 
first balls, the weakest of which contained §ds its weight of pla- 
tinum, might be very well substituted for the pure spongy metal. 
Freshly ignited, and allowed to cool, they became red when a jet of 
hydrogen was thrown upon them, and the gas itself then took fire. 
Put in contact with a mixture of two measures of hydrogen to one 
of oxygen, they became red, and an explosion followed, though 
not quite so rapidly as when spongy platinum was used. For ex- 
ample, when I put the ball No. 2. in 1*5 cubic inch of the explo- 
sive mixture, a dense dew formed on the mercury ; rapid dimi- 
nution succeeded, and in one or two seconds a dull light ap- 
