At the end of the eighteenth century, the Italian physicist Alessandro Volta invented the battery. By placing a pair of electrodes—one of zinc, the other of copper—in a solution that conducts electricity (sulfuric acid), he developed the principle that is still in use in today's dry-cell batteries.
More than half a century later there had been many new versions of the battery, but there were still problems with the original Voltaic design. The solution that conducts the electricity, usually some kind of acid, was too dangerous to touch and could spill out if the battery was tipped over. Nor were the electrodes very steady and were in danger of falling out if the battery was shaken too much. Furthermore, the batteries themselves were far too heavy to use around the house.
It was not until about 1866 that the French engineer Georges Ledanche (1839-1882) resolved these problems. Filling a porous pot with ammonium chloride, which is an alkaline rather than an acid, meant that a battery was less toxic. Replacing the lead electrodes used in earlier models with one of zinc and one of carbon-manganese dioxide created a much lighter battery. Finally, sealing the battery with a hard wax mixture, made it much more resilient against shocks and shakes and spillage.
Ledanche's design was tweaked again in 1887 by German scientist Carl Gassner who mixed the liquid ammonium chloride conductor with plaster of Paris to form a paste, which gave the world the first true dry- cell battery. Ledanche cells were extremely popular. They were used in doorbells, in cars, and, importantly, by Alexander Graham Bell in long-distance demonstrations of the telephone.
