102 Dr T urner's Experiments on the application of 
peared, which passed rapidly to vivid redness ; but by this time 
all the gas was consumed. With ball No. 3., the same results 
were obtained. Had I operated in these cases on a larger quan- 
tity of gas, there must have been an explosion. To prove this. 
No. 4. was put in 4 cubic inches of the explosive mixture; absorp- 
tion with dense watery vapour first appeared : in two or three 
seconds the ball became dull red, and passed rapidly, but during 
an appreciable space of time, to vivid redness, at which moment 
an explosion happened. The activity of these balls is greatly 
increased by heating them gently ; I have known No. 4. in that 
case inflame an explosive mixture of less than half a cubic 
inch. 
The balls No. 5, 6, 7, and 8., though not so powerful as the 
preceding, acted, nevertheless, with considerable energy. I put 
No. 8,, for example, in four cubical inches of the explosive mix- 
ture, expecting only a silent action ; to my surprise it became 
red, and caused an explosion. Nor would I venture to put 
Nos. 9, 10, and 11. in contact with much of the explosive mix- 
ture, for they act with an energy by no means to be expect- 
ed from the small quantity of platinum present. No. 12. was 
put into a half cubical inch of the explosive mixture : a very 
sluggish action ensued, but in the space of five minutes the gases 
were completely condensed. 
These experiments will convey a distinct idea of the extra- 
ordinary power of platinum, in causing the combination of oxy- 
gen and hydrogen gases, even when the quantity of metal pre- 
sent does not exceed one quarter of a grain, and that made up 
into a ball with fourteen times its weight of foreign matter. It is 
necessary to mention, that the gases I used in these experiments 
were of great purity, quite dry, and mixed in the exact propor- 
tion to form water. The oxygen was carefully prepared from 
dry chlorate of potash, and received over mercury. I prepared 
the hydrogen from zinc and dilute sulphuric acid, and collected 
it in a gas-holder over water. Successive portions of it were 
drawn off 1 when required, and dried over mercury by fused pot- 
ash. In the more delicate experiments I always ascertained its 
purity, and made due correction for the air it contained. If 
the gases are not mixed in the proper proportion to form water, 
,;ii silent but rapid combination is produced. I have never had any 
