470 



Rev. P. J. Kirk by on the Union of 



per cent, or less, be taken as the temperature necessary to 

 start the reaction. 



The latter temperature, 0, of the wire was calculated from 

 its resistance, R, by means of the formula 



6 



0o h p — (R— R ), 



ar\ 



R being the resistance which corresponds to the temperature 

 O . No correction was made, since the " platinum scale " is 

 practically identical with the centigrade scale for the 

 temperatures here determined. 



The resistance of the wire was found to be 2' 69 ohms at 

 18° centigrade, and a proved by experiment to be O0037, a 

 number which, by the way, testifies to the purity of the 

 platinum. When this number is put for a, and when 2*69, 

 18 are put for R , O respectively, the formula becomes 



0= 18 + 107 (R-2-69). 



Table I. gives the results of the experiments made with 

 the pure platinum wire. In this 



p = the pressure of the hydrogen and oxygen in mm. 



of mercury ; 

 C = the current in amperes which heated the wire to the 



temperature ; 

 R = the resistance of the wire in ohms when the current 



C was flowing in it ; 

 6 — the temperature centigrade of the platinum wire, 



at which it began to cause the chemical union of 



the gases. 



Table I. 



p. 



C. 



R. 



i 



e. 



397 



1-29 



5-17 



283 



36-0 



1-29 



5-2 



287 



176 



1-22 



513 



279 



9-6 



1-12 



5-13 



279 



8-9 



1-09 



5-03 



2G8 



8-6 



1-08 



5-0 



265 



4-3 



•97 



5-17 



283 



0-86 



-64 



5-6 



329 



It has been already pointed out that the method by which 

 was obtained might introduce an error of one per cent, 

 into 0. Other errors arise from the use of the voltmeter 

 and ammeter. But the total error to be expected in ought 

 not to exceed two per cent. Most of the numbers in the last 

 column may thus be said to be the same. The temperature 



