GAS MANTLES.

Taranaki Daily News, Volume L, Issue 61, 19 November 1907, Page 4

GAS MANTLES.

One of the most important illuminating appliances is the gas mantle, invented by Dr. Welshich, of Vienna, whose efforts, says Mr lies, "gave us on admirable example of an inventor passing from a hint to a test, day after day cnlties with unfailing soorcefulnesa." Tin- invention was the outcome o, t,n inv, siigotion of rare earths by Tl . '.Yelsbach, with the view of ascertaining their value as illuminants. After a number of experiments, he produced a mantle made with lanthanum oxide, which lie thought was just what was wanted' But after several days it crumbled £o powder, having attracted from the atmosphere both moisture and carbon dioxide. To overcome this defect, he added magnesia, but when it had been used for about 70 hours it failed in radiance, becoming glassy and translucent. Other rare earths were tried, including zirconium. Then thorium oxide was tested, with gratifying results. Vet when he had purified this substance to the utmost, the light fell off in on unaccountable'manner. Evidently in the purifying process some invaluable element had been cast aside. This was discovered by the researches of an associate, Mr Haitinger, to be cerium in minute quantity. As the result of many experiments it was found that 1 per cent of cerium and 99 per cent of thorium oxide are the best proportions for a mantle such as is used today. Nearly all the thorium required for mantles is found in the Monazite sands of Brazil, for a long time valued only for the zinc they contain. To-day the thorium is of far more account. It is sent for chemical treatment to Germany, whence the mantles are distributed to every quarter of the globe.