VOLTAIC ELECTRICITY. 



243 



FIG. 188. 



tions for the solution is as follows : One gallon of water, one pound 

 of bi cliromate of potash, and from a half -pint to a pint of sulphuric 

 acid, according to the energy of action desired. A small quantity 

 of nitric acid added to the solution increases the constancy of the 

 battery. 



{&.) The following recipe is good : Pour 187 CM. cm. of sulphuric 

 acid into 500 cu. cm. of water, and let the mixture cool. Dissolve 

 115 g. of potassium bi-chromate in 335 cu. cm. of boiling water, and 

 pour while hot into the dilute acid. When cool it is ready for use. 



384. Grove's Battery. The 



outer vessel of an element of Grove's 



battery contains dilute sulphuric acid. 



In this is placed a hollow cylinder of 



zinc. Within the zinc cylinder is placed 



a porous cup containing strong nitric 



acid. The negative plate is a strip of 



platinum placed in the nitric acid. The 



hydrogen passes through the porous cup and reduces the 



nitric acid to nitrogen peroxide, which escapes as brownish 



red fumes. A Grove's element is represented in Fig. 188. 



385. Bimsen's Battery. Bunsen's battery differs 



from Grove's in the use of car- 

 bon instead of platinum for 

 the negative plate. The ele- 

 ments are made larger than 

 for Grove's battery. It gives 

 greater quantity and less in- 

 tensity than Grove's ( 380 [a]). 

 A Bunsen's element is repre- 

 sented in Fig. 189. 



p g Note. There are scores of dif- 



ferent batteries in the market com- 

 peting for favor. With the exception of Smee's, those here 

 described are the ones most commonly used. 



