104 Hr T timer’s Experiments on the application of 
nation. The very same occurred in a mixture of 5 air to 1 hy- 
drogen. Ball No. 3. had a distinct action in mixtures of 30 and 
40 air to 1 of hydrogen. 
It is then apparent from these experiments, that the plati- 
num balls caused the formation of water, when a strong electri- 
cal charge did not do so. It appears, too, that the balls acted 
so powerfully in a mixture of air and hydrogen, that electricity, 
afterwards employed, had no effect. The platinum is likewise 
shown to act with great velocity; for, after the short space of one 
minute, so large a quantity of hydrogen had disappeared, that the 
residual gas was not explosive. I have, within a few days, seen 
a short article by Professor Gmelin of Tubingen, published in 
a recent Number of the Annales de Chimie et de Physique , in 
which he states, that a mixture of air and hydrogen, after it 
had been acted on by platinum, still contained so much hydro- 
gen as to detonate from the electric spark. He concludes, 
therefore, and justly, were his experiments correct, that plati- 
num cannot be employed in eudiometry. He does not mention 
how he operated, and therefore I cannot perceive the source of 
his error. 
I now proceeded to inquire, whether the exact quantity of 
hydrogen was indicated by the action of platinum. 
In a mixture of 5 air to 1 hydrogen the diminution oc- 
casioned by an active ball indicated within a fraction the quan- 
tity of hydrogen present ; and in a mixture of 9 air to 1 hy- 
drogen the quantity of the latter was again correctly indicated. 
These experiments were performed once and again with simi- 
lar results. 
In mixtures of 13 air to 1 hydrogen, 15 to 1, 17 to 1, and 
19 to 1, the quantity of hydrogen was very accurately indica- 
ted, and the brilliancy of the mercury round the ball was in 
each case sullied by the formation of dew. 
I mixed 5 volumes of hydrogen with 500 of air, or in the 
exact proportion of 1 : 100. The ball No. 2., gently warm- 
ed, was put into 180 volumes of this mixture, which, of 
course, contained 1.8 of hydrogen. In half an hour there was 
diminution of 3 volumes, which indicates the presence of 
Q hvdrogen. 
