1889.] 



A new Form of Gas Battery. 



297 



well as later investigators, overlook one important point, viz., the 

 necessity of maintaining the condensing power of the absorbent 

 unimpaired. We found that platinum, black, the most suitable 

 absorbent for gas batteries, loses its condensing power almost com- 

 pletely as soon as it gets wet, and that it is therefore necessary for 

 our purpose to keep it comparatively dry. All attempts to attain this 

 with various constructions of the gas battery involving the use of a 

 liquid electrolyte failed. "We have only succeeded by using an elec- 

 trolyte in a quasi-solid form, viz., soaked up by a porous non-conduct 

 ing material, in a similar way as has been done in the so-called dry 

 piles and batteries. 



In order to procure as large a contact as possible between the gases, 

 the electrolyte and the absorbent, and at the same time to obtain the 

 greatest possible duty out of a given quantity of the latter, we have 

 adopted the following construction : — 



A diaphragm of a porous non-conducting substance, such as plaster 

 of Paris, earthenware, asbestos, pasteboard, &c, is impregnated by 

 dilute sulphuric acid or another electrolyte, and is covered on both 

 sides with thin perforated leaf of platinum or gold and with a thin 

 film of platinum black. The platinum or gold leaf, which serves as 

 conductor for the generated electricity (the platinum black being a 

 very bad conductor), is placed in contact at small intervals with 

 strips of lead or other good conductor in order to reduce the internal 

 resistance of the battery to a minimum. In place of the platinum or 

 gold leaf, fine wire gauze of the same metal or of carbon may be used. 



The diaphragms so prepared are placed side by side or one above 

 the other, with non-conducting frames of pasteboard, wood, india- 

 rubber, &c, intervening, so as to form chambers through which the 

 gases to be employed (generally hydrogen and air) are passed, so that 

 one side of the diaphragm is exposed to the one gas and the other to 

 the other gas, and the spaces between the diaphragms are so con- 

 nected that these gases pass in contact with a number of diaphragms. 



Of the numerous ways in which dry gas batteries can be con- 

 structed we will describe two. One of these constructions, suitable 

 for laboratory work, shown in fig. 1, consists of an earthenware 

 plate M, impregnated with sulphuric acid and cemented into an 

 ebonite frame R. 



At a short distance from and all around the plate a copper wire A 

 is let into the ebonite frame. The earthenware plate is covered with 

 platinum leaf which has been perforated with a very large number 

 (1500 per square cm.) of small holes, and which extends over and is 

 in metallic contact with the copper wire. To protect the latter from 

 corrosion, and to avoid local action, molten paraffin is put over the 

 platinum leaf where it is in contact with the copper wire. Where the 

 platinum leaf is in contact with the earthenware plate it is coated by 



