HYDROGEN AND OXYGEN IN CONTACT WITH HOT SURFACES. 
13 
The Absorption Apparatus. 
Whenever it was necessary to test the power of a given surface to absorb hydrogen 
(or oxygen) at higher temperatures than could be obtained with the Lothar Meyer 
furnace of the circulation apparatus, the combustion tube containing the catalysing 
material was transferred to the “absorption apparatus” shown in Diagram I., fig. 4. 
This consisted of a high-temperature furnace, properly screened by an asbestos hood 
and placed symmetrically with regard to the two ground-glass mercury cup joints 
cV, into which the combustion tube exactly fitted. One of these joints was fused on 
to the three-way tap X, through which connection could be made either with an 
automatic Sprengel pump or a syphon manometer. The other joint was similarly 
fused to the tap Y, which served to connect the apparatus with the gas-holder 
containing the hydrogen (or oxygen). In making an experiment, the combustion 
tube was first of all thoroughly exhausted and heated to the desired experimental 
temperature (usually about 650°), which was kept constant by the employment of a 
Stott’s governor in connection with the gas supply of the furnace. The gas under 
examination was then admitted from the holder, and the absorption (if any) followed 
by taking pressure readings every few minutes. When the material was fully 
charged, the furnace was turned out and the unabsorbed gas pumped out in the cold. 
Finally, the combustion tube was again heated to the experimental temperature and 
any occluded gas pumped out and collected for examination. In this way the 
rapidity and extent to which a given surface occluded the gas was measured, and, by 
afterwards transferring the combustion tube with its contents back again to the 
circulating apparatus, the influence of repeated occlusions on its catalysing power w r as 
determined. 
Part I. —Experiments with Porous Porcelain. 
In these experiments the combustion tube of the apparatus was closely packed with 
fragments of unglazed porous porcelain which had been previously heated to 1000° in 
a muffle furnace. The material was perfectly white in colour and presented a large 
surface to the reacting gases. Its average composition was as follows :— 
Per cent. 
Silica. 7575 
Alumina.. . 21‘30 
Ferric oxide. 0'05 
Per cent. 
Calcium oxide.1‘45 
Magnesium oxide. 0’35 
Sodium and potassium oxides . 070 
During the course of the research, altogether five different surfaces of this material 
were employed. The results obtained with all five surfaces were the same in three 
important particulars, namely (1) that with normal electrolytic gas the rate of 
combination was always proportional to the pressure of the dry gas; (2) that with an 
