HYDROGEN AND OXYGEN IN CONTACT WITH HOT SURFACES. 
15 
Diagram II. Experiments with porcelain. Pressure curves for normal electrolytic gas. 
combination is proportional to the pressure of the dry gas, the values of “ k 1 ,” 
1 C 
calculated from the expression — log , being remarkably constant throughout each 
experiment, even though the total pressure varied over a wide range. 
Second Series.—Experiments with Surface B at 430°. 
This surface had been previously used for experiments on the catalytic combination 
of carbon monoxide and oxygen, during the course of which it had settled down to a 
very steady condition as regards its catalysing power. Before being packed into the 
combustion tube of the apparatus, the material was thoroughly burnt out at red heat 
in a current of air. Neither the tube nor its packing was changed throughout the 
whole of the following series of experiments (III. to XX. inclusive), which may be 
sub-divided into three groups, according to the special objects in view in each case. 
ls£ Group .— With Normal Electrolytic Gas. 
This group comprised two experiments with normal electrolytic gas. In Experi¬ 
ment III. the rate of circulation was 1 in 20 minutes, and in IV. 1 in 30 minutes, 
otherwise the conditions were the same. As might be expected, the absolute rate of 
