OCCLUSION OF OXYG-EN AND HYDROGEN BY PLATINUM BLACK. 
133 
pure lead and zinc were determined, to see that everything was in good working 
order. The values we found were as follows :— 
Specific heat of lead . 
Spring found . . . 
Specific heat of zinc . 
Kopp found. 
Bunsen found .... 
Schuller and Wartha form 
0'0290 between 
r 0-0305 ,, 
I 0-03195 
10-03437 
0‘09312 between 
0° and 38°0 C. 
17° ,, 108° „ 
13° „ 197° „ 
1G° „ 292° „ 
0° and 15°-8 C. 
. 0-0932 
. 0-0935 
d 0-0939 
I Temperature interval not 
f stated. 
j 
The numbers we find are lower than those recorded by other observers, but this, 
at least in the case of lead, is as it should be, since the determination was made at a 
lower temperature. 
Having satisfied ourselves that the instrument gave correct results, an experimental 
tube of the form shown in fig. 1 was made. It consisted of a bulb, D, to contain the 
platinum black, which along with a portion of the stem was immersed in the salt 
solution contained in the inner tube of the calorimeter. Communication between the 
bulb and the system of taps and capillary tubes which projected above the calorimeter 
was made by means of a tube F, just sufficiently wide to admit of the introduction of 
the platinum black. When the experimental tube was in position, the mouth of the 
inner tube of the calorimeter was closed by the india-rubber stopper F. After a 
known weight of ])latinum black had been introduced, and before the apparatus was 
finally fixed in position in the calorimeter, the tube F was sealed off at the point A. 
The tube B was now connected with a gas burette whilst C was placed in communi¬ 
cation with the pump, and the capacity, of the tube determined by filling with dry air 
at a known temperature and pressure, exhausting and remeasuring at the same 
tempei-ature and pressure. 
The platinum black wms now fully charged up by admitting i)ure hydrogen under 
atmospheric pressure. After standing for a day, the tube was jacketed with aniline 
vapour at 184°, and the excess of hydrogen filling the apparatus, together with the 
hydrogen and water which can be removed in vacuo at the ordinary temperature, and 
that which is given off at 184° C., extracted by means of the pump. Both taps being 
now shut, the experimental tube in a vacuous state was cut off, cooled to 0°, and 
introduced into the calorimeter. In this position it was again connected up with the 
hydrogen apparatus and the pum]i, and when equilibrium had set in, hydrogen was 
admitted, from a gas burette, and the deflection of the mercury meniscus in the 
capillary side tube, G, noted from time to time until equilibrium was presumably again 
established. As a rule the position of the meniscus in the capillary tube never 
remains stationarv, whether an experiment is in progress or not, in consequence of 
