1889.] the Chemistry of Sto rage Batteries. 307 



as is seen from the following comparison :— 



Calculated. Found. 



So 64 7-57 7-78 



Pb 3 621 73-49 73-41 



O 10 160 18-94 18-44 



845 10000 99-63 



The composition of this salt may be represented graphically 

 thus : — 



O 



2 =S=0 2 =Pb 



\) =S=Oo=Pb 



O 



The formation of this salt is expressed by the following equation : — 

 Pb 3 4 + 2S0 4 H 2 = S 2 Pb 3 O 10 + 2OH 2 . 



Minium. Sulphuric Red lead Water, 

 acid. salt. 



These then are the salts which constitute the original active material 

 of storage cells when that material is formed by the admixture of 

 sulphuric acid with litharge or minium respectively, and it is highly 

 probable that one or the other of these salts takes part in the elec- 

 trolytic processes of the storage battery. It is fortunate that these 

 hitherto unknown salts (and not the ordinary kuown sulphate; are 

 formed in the cell reactions ; for, in the alternative case, lead storage 

 batteries would be practically valueless. 



If the buff lead salt be the active material of the battery plates, 

 then the following equations express the electrolytic reactions taking 

 place in the cell: — 



I. In charging — 



(a.) Positive Plates. 



S 8 Pb 5 O u + 30H 3 + 3 = 5Pb0 2 + 3S0 4 H 2 . 

 Buff lead Water. Lead Sulphuric 



salt. peroxide.* acid. 



(6.) Negative Ptates. 

 S 3 Pb 5 14 +5H 2 = 5Pb-h3S0 4 H 2 + 20H 2 . 



* Mr. Fitzgerald considers that this peroxide is hjdrated. 



