102 



Prof. J. J. Thomson. 



[Mar. 9 T 



Spark 



Metal 



Excess of H 



Excess of O 



H in 



Duration of 



len °iA\ in 



used for 



m tube next 



in tube next 



water 



experiment 



millimetres. 

 > 



electrodes. 



+ electrode. 



— electrode. 



voltameter. 



in minutes. 







c.c. 



c.c. 



c.c. 





1 5 



gold 



3 '25 



1 -5 



3 2 



40 



1 5 



platinum 



2-8 



1 6 



3 -0 



30 



1*5 



gold 



1-7 



-8 



1 -8 



20 



2-0 



gold 



2-0 



1 -08 



1'95 



30 



2-0 



gold 

 platinum 



3 25 



1-75 



3 2 



60 



2-0 



1-8 



tube broken 



2-0 



not noted 



2-0 



platinum 



3-0 



1-5 



3-0 



60 



2 -0 



gold 



2 5 



1-5 



3-0 



60 



3-0 



gold 



1 -8 



not noted 



1-8 



not noted 



3-0* 



gold 



0-7 



0-4 



0-8 



90 



3 "Of 



gold 

 gold 



1 *b' 



not noted 



1 *75 



not noted 



4-0 



0-9 



0-37 



0-7 



20 



4 



gold 



2 75 



I -25 



2-7 



60 



4 -Of 



gold 



10 



not noted 



1-25 



not noted 



4-0 



gold 



2-5 



125 



2-3 



45 



equal to that from the water, it is, when the increase in the spark 

 length is not too large, considerably greater. 

 The following are a few instances of this : — 



Hydrogen Hydrogen 



Spark length. from steam. from voltameter. 



5 mm. 1-8 T2 



5 „ 3'75 3-0 



5 „ 4-4 2-1 



6 „ 4-0 1-6 



7 „ 4-25 3-0 



7 „ 3-75 2-0 



8 „ 3-75 2*6 



This increase in the ratio of the hydrogen from the steam to that 

 from the voltameter does not continue when the length of the spark 

 is still fnrther increased. When the spark length has got to 8 mm. 

 this ratio begins to fall off very rapidly as the spark length increases, 

 and we soon reach a spark length at which it seems almost a matter 

 of chance whether hydrogen or oxygen appears in the collecting tube 

 connected with the positive electrode. 



When the sparks are at this critical length the kind of thing which 

 happens is somewhat as follows : — For some time an excess of hydro- 

 gen (say) comes off in the tube next the positive electrode, and 

 accumulates as the mixed gases are exploded ; then some slight 



* In this experiment a slow mercury break making about four breaks per second 

 was used. 



f In these experiments large Leyden jars were attached to the electrodes. 



