DEFECTS OF COMMON ACID BATTERIES. 33 



The zinc and copper are connected together by a binding screw. 

 To construct this battery the zinc plates are put in first, being made 

 to slide in grooves, cut in the sides of the trough, the plates stand- 

 ing in the centre of their respective cells : the copper plates are put 

 in, and the copper bands marked c are made fast to the zincs by 

 binding screws, care being taken that the parts where they are con- 

 nected are clean and bright, and that the copper and zinc touch no 

 where else. A battery of nine pair can be fitted up and made ready 

 for action in ten minutes. 



In fitting up batteries of this sort, we are aware that sometimes 

 great care is taken that the partitions in the trough be perfectly 

 water tight, and .also formed of some non-conducting material, such 

 as glass, or of wood, either pitched or saturated with some non-con- 

 ducting substance ; but we have found in practice that these pre- 

 cautions are not required, the principal thing to attend to being, 

 that the metals should not be allowed to touch, except in their 

 proper connections. 



Defects of Common Acid Batteries. Although we have spoken 



thus favourably of the principles upon which Wollaston's battery is 

 constructed, still as a philosophical instrument it is far from being 

 perfect : hence the many modifications of it which have been recom- 

 mended. Indeed, electro-chemists, since the time of Volta, have 

 been endeavouring to invent an instrument free from the defects 

 which attach to Wollaston's one capable of giving, at the same 

 time, a constant and powerful current, abundant in quantity and of 

 great intensity. The success and results of these endeavours are so 

 closely connected with the art of electro-metallurgy, and the know- 

 ledge of them is so essential to a successful prosecution of the art, that 

 we must not be sparing in our descriptive details. 



In operating with a Wollaston's battery, or any other arrangement 

 composed of similar elements, such as zinc, sulphuric or muriatic 

 acid, and copper, silver or platinum, it will be found that the 

 current of electricity obtained diminishes in quantity and strength 

 in proportion to the time of action. This is the result of various 

 causes : 



1st. The hydrogen which is evolved at the surface of the negative 

 metal in the battery, which we shall say is copper, adheres with con- 

 siderable force to the surface of the metal, and consequently obstructs 

 its superficial influence, so that the quantity of electricity which the 

 surface of the two metals are calculated to give is much lessened. 



2d. After the battery is in action a short time, a portion of the 

 sulphate or chloride of zinc, formed in the battery by the solution 

 of the zinc, becomes reduced upon the surface of the copper. This 

 reduction is supposed to be owing to the electrolyzation of the zinc 

 solution by the passage of electricity, but it is, more probably, caused 



