NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 85 



INVENTION OF THE TUNGSTEN LAMP 



Alexander Just and Franz Hanaman in 1902 were laboratory assis- 

 tants to the Professor of Chemistry in the Technical High School in 

 Vienna. Just was spending his spare time in another laboratory in 

 Vienna, attempting to develop a boron incandescent lamp. In August 

 of that year he engaged Hanaman to aid him in his work. They con- 

 ceived the idea of making a lamp with a filament of tungsten and for 

 two years worked on both lamps. The boron lamp turned out to be 

 a failure. Their means were limited ; Hanaman's total income was 

 $44 ])er month and Just's was slightly more than this. In 1903 they 

 took out a German patent on a tungsten filament, but the process they 

 described was a failure because it produced a filament containing 

 both carbon and tungsten. The carbon readily evaporated and quickly 

 blackened the bulb when they attempted to operate the filament at an 

 efficiency higher than that possible with the ordinary carbon filament. 

 Finally in the latter part of the next year (1904) they were able to 

 get rid of the carbon and produced a pure tungsten filament. 



Tungsten had been known to chemists for many years by its com- 

 pounds, its oxides and its alloys with steel, but the properties of the 

 pure metal were practically unknown. It is an extremely hard and 

 brittle metal and it was impossible at that time to draw it into a wire. 

 Just and Hanaman's process of making a pure tungsten filament con- 

 sisted of taking tungsten oxide in the form of an extremely fine 

 powder, reducing this to pure tungsten powder by heating it while 

 hydrogen gas passed over it. The gas combined with the oxygen 

 of the oxide, forming water vapor which was carried off, leaving the 

 tungsten behind. 



The tungsten powder was mixed with an organic binding material, 

 and the paste was forced by very high pressure through a hole drilled 

 in a diamond. This diamond die was necessary because tungsten, 

 being so hard a substance, would quickly wear away any other kind of 

 die. The thread formed was cut into proper lengths, bent the shape of 

 a hair pin and the ends fastened to clamps. Current was passed 

 through the hair pin in the presence of hydrogen gas and water 

 vapor. The current heated the hair pin, carbonized the organic bind- 

 ing material in it, the carbon then combining with the moist hydrogen 

 gas, leaving the tungsten particles behind. These particles were 

 sintered together by the heat, forming the tungsten filament. Patents 

 were applied for in various countries, the one in the United States on 

 July 6, 1905. 



