525 
Rev. T. R. Robinson, D. D., read a paper on the effect 
of Heat in lessening the Affinity of the Elements of Water. 
The author referred to the experiments of Mr. Grove on 
the decomposition of water by the action of incandescent pla- 
tinum ; and, after noticing the objections which were urged 
against its being caused by heat, detailed results which he 
had obtained at a much lower temperature, and which ap- 
peared to him to accord with that hypothesis. 
Proceeding on the theory of the voltaic circuit, which 
Ohm has given, he investigated the diminution of electric 
intensity, which is caused by placing in the circuit a cell where 
water is subjected to voltaic decomposition, and shewed that 
it is equal to the affinity of platina for oxygen minus twice that 
of hydrogen for oxygen, or 
e = op — 2ho. 
This quantity e can be measured by the instruments and pro- 
cesses described by Mr. Wheatstone in the Philosophical Trans- 
actions for 1843, with some modifications, which, in the au- 
‘thor’s opinion, increase their accuracy. After describing the 
apparatus he used, he finds for the value of e, 
At the temperature 61°. . . e€=598.9 . . . 12 obs. 
136°.4 00.5% GGTBy 20sc8 AS 
1 ae B31O 32.92 
These give, for an increase of temperature of 100°, the decrease 
of the affinity of the oxygen and hydrogen of water = 23.2. The 
author applies to this result the theory of probabilities, which 
has so much advanced astronomical and physical science ; and 
finds the chances to be 10,000 to 1 that it is not all error of 
observation. 
It might be objected, that this diminution of e is due to 
the expansion of the gases by heat enabling them to escape 
more freely from the electrodes. This was tested by placing 
