in the Discharge through Gases at Low Pressures. 153 
only in the case cf platinum that cathodes of larger and 
smaller dimensions were used *. 
We have calculated from Granquist’s values the disinte- 
eration for a time of discharge of 30 minutes and a current- 
streneth of 20 scale-divisions = 2°49x10-% amp., on the 
assumption that the disintegration was proportional to the 
current-strength, which assumption seems to be at least 
approximately true according to our own observations. We 
leave out of account the difference in current-density, as 
Granquist’s Table I. shows that with increasing current- 
density the disintegration and potential increase in the same 
ratio. 
TasBLe I1.—Observations of Granquist. 
| 
| 
| 
| | y,(mg. x 10—}). | y(mg. x 10—}). 
: | Pp | y | i P V aeons ee ee 
; (mm. Hg) (Volts) | | ; (mm. Hg) (Volts) 
| | Obs. |Obs. — Cal. Obs. ‘Obs. —Cal. 
Gold. Platinum. 
Peeves 11050} 80 | — 3 *90 | O89 1300 | 55 
Loerie 940) :74 | +3 *« 20 038 1075 | 43 ay 
20 | O27 | 885 | 485 | —12 20 0-38 25 | 30 
30 Ooo | 825 | 51 | — 5 * 20 038 600] 15 
30 O39 | 725/45 | +1 
20 (29) 625) 34 | +1 ‘ ie p S 
20 039 | 625| 3251 oO oF Boece. lee 
Si ee Be 25 054 920] 32 a7 
ee | 222 |. 0 2 | 054 | 835| 20 -8 
Silver 2 fae aay an 4 
9) “de ») Z 
20, 013 | 1050) 44 =i 35 0:95 625 iS-5 a3 
Pasi) | 733) 205|  —5 53 0:95 | 5801 13 
20 | 023 | 700! 19 fei 23 OO54 be 515 |e 1 
205 | O31 | 625 | 14 a4 
205 | O17 | 1830] 63 +6 
Copper. Ries 0:20 1265| 48 =5 
Pee 020) (1410499, (1 | te. 2l 0:23 985 | 46 +9 
Peel |) 11380.) 16). |. +1 | 21 0°38 835 | 30 2 
eee Oey? (11501 3) | 9 20 054 885] 20 eS 
HO 47 1) 5908). 5 do). eos 095 | 580] 13 
28 HEI. hn OS, a en 23 095 |1515 | 12 Be 
The values of v, are calculated from the equations :— 
Gold,  —_ y,=0°118(V —350) =0:00060A(V —350) ; 
Silver, 7, =0-0648(V —350)=0-00060A(V —350) ; 
Copper, ,=0-0191(V —350)=3A x 0:00060(V — 350) ; 
Platinum, 7,=0-0584(V —350)=3A x 0-00060(V —350). 
'* The observations when the cathodes had other dimensions are 
marked with an asterisk. 
