Page:Collected Physical Papers.djvu/321

Rh exhibits the increased response due to the action of Na$2$CO$3$ on Pt. Another record shows an exactly similar effect on tin. The record of effect was taken two minutes after the application. Other records taken immediately after, show that the enhanced responsiveness takes place gradually with time.

Depressants.—Reagents, like KBr (10 per cent.), produce a depression in the response. There are again others which abolish the response almost completely, for example, 3 per cent. KHO solution (fig. 82, c). One of the most effective reagents which abolishes the response is oxalic acid. The depressing effect of this reagent is so great that a strength of 1 part in 10,000 is often sufficient to produce an abolition of response.