NO. 2 



HISTORY OF ELECTRIC LIGHT SCHROEDER 



13 



GRENET BATTERY 



It was discovered that chromic anhydride gives up oxygen easier 

 than nitric acid and consequently if used would give a higher voltage 

 than Grove's nitric acid battery. It also has the advantage of a lesser 

 tendency to attack zinc directly if it happens to come in contact with it. 

 Grenet developed a cell having a liquid consisting of a mixture of 

 potassium bichromate (K2Cr207) and sulphuric acid. A porous cell 

 was therefore not used to keep the two liquids apart.. This had the 



Grove's Incandescent Lamp, 1840. 



Grove made an experimental lamp, using platinum for the burner 

 which was protected from, draughts of air by a glass tumbler. 



advantage of reducing the internal resistance. The chemical reaction 

 was: 



KoCraOy (potassium bichromate) +7H2SO4 (sulphuric acid) + 3Zn 

 (zinc) =3ZnS04 (zinc sulphate) +K2SO4 (potassium sulphate) 

 + Cr2 (504)3 (chromium sulphate) +7H2O (water). 



In order to prevent the useless consumption of zinc on open circuit, 

 the zinc was attached to a sliding rod and could be drawn up into the 

 neck of the bottle-shaped jar containing the liquid. 



DE MOLEYNS' INCANDESCENT LAMP 



Frederick De Moleyns, an Englishman, has the honor of having 

 obtained the first patent on an incandescent lamp. This was in 1841 

 and his lamp was quite novel. It consisted of a spherical glass globe, 

 in the upper part of which was a tube containing powdered charcoal. 

 This tube was open at the bottom inside the globe and through it ran a 



