PHILOSOPHICAL TRANSACTIONS. 
I. The Bakerian Lecture. — On certain Phenomena of Holtaic Ignition and the 
Decomposition of Water into its constituent Gases hy Heat. 
By W. R. Grove, Esq., M.A . , F.R.S. 
Received September 3, — Read November 19, 1846. 
IN the Philosophical Magazine for August 1841 , I recommended for eudiometrical 
purposes, the use of a platinum wire ignited by a voltaic battery. In Plate I. fig. 1, 
is represented a form of apparatus for this purpose ; it consists of a tube of Bohe- 
mian glass, with a loop of platinum wire ^ 0 -th of an inch diameter sealed into its 
upper end ; the size of the glass tube may be adapted to the quantity of gas sought to 
be analysed, and may when necessary be reduced to extremely small dimensions, one- 
eighth of an inch being ample; into this the gas may readily be made to ascend, by 
the insertion of a wire of copper, platinum, or glass, as may be suitable to the gas : 
two cells of the nitric-acid battery are sufficient fully to ignite the wire, and the same 
battery supplies, by electrolysis, pure oxygen and hydrogen for the analysis. Since 
the period when I first proposed this, I have seldom used any other apparatus for such 
gaseous analyses as are performed by combining the gas to be examined with oxygen 
or hydrogen. This eudiometer possesses the advantage of enabling the operator 
either to detonate or slowly to combine the gases, by using different powers of battery, 
by interposing resisting wires, or by manipulation alone, — a practised hand being 
able by changing the intervals of contact to combine or detonate the gas at will. My 
general practice has been to produce a gentle heat in the wire until the gases con- 
tract, and then gradually to increase the heat until a full ignition takes place, by 
which means all the objects of the eudiometer of Volta are fulfilled, without detona- 
tion, without dependence on the fickle electric spark, and without thick tubes, any 
danger of explosion, or of the gases being projected from the eudiometer. 
I have commenced with a description of this eudiometer, as it has been indirectly 
the means of my undertaking the experiments detailed in this lecture ; and as its very- 
great convenience has never been generally understood, I think that in strongly re- 
commending it, I shall be of service to chemists. 
MDCCCXLVII. 
B 
