of thorium. In 1916 the United States imported 2,500,000 pounds of
monazite from Brazil and India, most of which used to go to Germany. In
1895 we got over a million and a half pounds from the Carolinas, but the
foreign sand is richer and cheaper. The price of the salts of the rare
metals fluctuates wildly. In 1895 thorium nitrate sold at $200 a pound;
in 1913 it fell to $2.60, and in 1916 it rose to $8.
Since the monazite contains more cerium than thorium and the mantles
made from it contain more thorium than cerium, there is a superfluity of
cerium. The manufacturers give away a pound of cerium salts with every
purchase of a hundred pounds of thorium salts. It annoyed Welsbach to
see the cerium residues thrown away and accumulating around his mantle
factory, so he set out to find some use for it. He reduced the mixed
earths to a metallic form and found that it gave off a shower of sparks
when scratched. An alloy of cerium with 30 or 35 per cent. of iron
proved the best and was put on the market in the form of automatic
lighters.
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