CHAPTER VI
THE PHOSPHATES AND HALIDES
(a) The Phosphates
Monazite, Phosphocerite.
—Monazite, by far the most important, commercially, of all the rare earth minerals, is essentially an orthophosphate of the ceria earths, of the formula R´´´PO₄.[97] The yttria earths are usually present in small quantities. Silica and thoria, in quantities varying from traces up to 6 per cent. of the former and from 1 to 20 per cent. of the latter, are invariable constituents; it is almost entirely to the percentage of thoria that the mineral owes its commercial value. The following also are common constituents, though usually in very small quantities only—stannic, ferric and manganous oxides, alumina, lime, magnesia, zirconia and water. Helium was observed in it by Tilden, and by Ramsay, Collie and Travers.[98] Boltwood[99] and Zerban[100] found uranium in it; the latter attributed this to impurities, the former regarded it as an essential constituent. Strutt[101] found uranium in a pure monazite. Haitinger and Peters[102] detected radium, their result being confirmed by Boltwood and Strutt.
[ [97] For the composition of the earths in monazite, see James, J. Amer. Chem. Soc. 1913, 35, 235.
[ [98] Trans. Chem. Soc. 1895, 67, 684.
[ [99] Phil. Mag. 1905, [vi.], 9, 599.
[100] Ber. 1905, 38, 557.
[101] Proc. Roy. Soc. 1905, A, 76, 88 and 312.
[102] Sitzungsb. kaiserl. Akad. Wiss. Wien, May, 1904.