Welsbach patent

The only important commercial use of thorium, however, is in the manufacture of incandescent gas mantles. This industry had a very modest beginning in 1884 when Welsbach patented the use of a fibrous network of rare earth oxides which were to be heated by an ordinary gas flame of the Bunsen type. The first mantles were composed of a mixture of zirconia, lanthana,... 

Period of First Industrial Usage. By iitprovement of this first discovery there arose the first industrial consunption of rare earths and the hour of birth of the rare earth industry in the year 1891, when Auer vcn Welsbach reported his patents for the Auer incandescent mantle v ch is conposed of 99 % thorium oxide and 1 % cerium oxide. Ihis light was sip>erior for decades to electric light. It was cheaper so that until the year 1935 approximately 5 billion incandescent mantles had been produced and consumed in the world. 

The carbon filament lamp vAiich was developed in parallel at the beginning of this century was always several times as expensive in use as an Auer incandescent mantle. As a result, this first use of the rare eaurth elements achieved great economic success and thanks to his capabilities Auer von Welsbach played a major role in this worldwide achievement. He was in the position to survive the extraordinarily corplicated and obstinately pursued patent battles. 

In ignition, electric incandescent lartps were far superior to the Auer lights. But this situation was ameliorated in 1903 vhen von Welsbach was granted a patent for a pyrophoric metal alloy ("flintstone") ccnposed of 70 % mischmetal and 30 % iron, Ihis patent was also streniKxisly litigated but victoriously defended. 

Welsbach first patented thoria as the mantle material,40 believing that it was possessed of high capacity for light emissivity. He later found that the brilliant luminosity of his early products was due to the presence of small amounts of ceria. The addition of about 1 per cent of ceria to the thoria used in making the mantles resulted in a mantle with over ten times the emissivity of those containing no ceria. Further addition of ceria, however, resulted in a progressive diminution of brilliance until when as much as 10 per cent had been added the luminosity was again small. 

Welsbach s incandescent gas mantle patented in 1885 enabled the gas industry to compete for a few more decades with electric lights. 

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