402 



Prof. V. B. Lewes. 



[Mar. 7, 



It is well known that hydrogen will diffuse through ignited 

 platinum into a vacuous space or even into other gases, and although 

 no change in volume was observed when a mixture of 95 per cent, 

 hydrogen and 5 per cent, ethylene was passed through the tube 

 heated to 900 C., it seemed advisable to make special experiments to 

 ascertain if any loss of hydrogen from this cause did take place at 

 the temperature employed. 



The apparatus having been fitted up as before, 6 in. of the tube 

 were heated to between 900 and 1000 0., and a carefully measured 

 volume of pure hydrogen was made to pass through it three times at 

 a slow rate of flow, with the result that, after being brought back to 

 its original temperature and pressure, it measured 99'5 per cent, of the 

 volume taken, showing that error from this cause is not likely to 

 have taken place. 



, A new series of experiments was now undertaken to ascertain, if 

 possible, how increase of contact with the heated walls of the con- 

 taining vessel affected the amount and character of the decomposition 

 taking place. 



In order to do this, a small platinum tube 2'5 mm. in diameter and 

 45*72 cm. long was taken in place of the one used in the previous ex- 

 periments, which was 14 mm. in diameter. The area of the big tube 

 therefore, as compared with the area of the small tube, was as 1'54 to 

 0'049, and in order to obtain the relative amount of decomposition it 

 is manifest that the rate of flow must be the same in both tubes. 



If the rate of flow in the big tube be 40 c.c. per minute, then 



2-5 2 x40 



= 1-27 



will give the required rate for the small tube. 



Table V. Temperature, 900 C. Rate of Flow, 1*27 c.c. per minute. 



