399 



l„^=(h;;'(öj' = io2x-48 



if will be seen, that for the surrouiKÜng liquid layer which is in 

 electromotive eqiii librium with magtiesiiun and hydrogen the 

 following formula holds good : 



(Me") L„ 



^ ^L^ _ _M« _ 102x32 



It is evident that this ratio is not renlizable. 



If we chose (Mgp = 1 ihen(H^)' =10^x32 and since (H^XOHj^) = 



= 10-1* ^ve iiave (OH'^^) = IQis. 



If we take (Mg") = lO-i then (H,\ = 10-2* or (OH;) = ]Oio. 



From the above figures it is seen that if magnesium is in such a 

 state that the solubility |)roduct is 10"' ~^'' it can never coexist 

 with unary hydrogen and li(|uid because the surrounding liquid 

 layer, required for this coexistence, cannot exist. 



A graphical representation of the above statement in £", A' diagram 

 (fig. J), is given by the point C. C lies so near one axis that any 

 stable aqueous solution lies to the right of it. If we assume that the 



Fig. 1. 



solution into which the Mg electrode is dipped has the composition 

 X then (here are two limiting possibilities for the coexistence of 



