Page:On Electromotive Wave accompanying Mechanical Disturbance in Metals in Contact with Electrolyte.djvu/18

290 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 2 minutes after the application. Other records taken immediately after, show that the enhanced responsiveness takes place gradually with time. (See also fig. 7, and compare the general similarity between the enhancement of response produced by preliminary vibration and by the action of Na$2$CO$3$.)

Depressants—Other 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. 12, 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.

Opposite Effects of Varying Strengths of Soloution.—The most curious effect is that exhibited by some reagents when the strength of solution is varied. This is clearly seen in the following record (fig. 12), in which

(a) gives the normal response in water. KHO solution was now added so as to make the strength 3 parts in a thousand and (b) shows the