[578] J. Soc. Chem. Ind. 1912, 31, 830.
[579] Ibid. 1911, 30, 1128.
The fluoride, silicofluoride, and dioxide have also been proposed for the preparation of enamels,[580] but do not give satisfactory results.
[580] Rickmann and Rappe, D. R. P. 99165, September, 1898; also D. R. P. 203773, October, 1908.
Several patents protect the use of rare earth compounds for flashlight powders. For most of the mixtures covered, it is claimed that the usual defects of fumes, slow firing, etc., are absent. The usual recipes[581] are for magnesium or aluminium powder with chromates, nitrates, or similar salts of thorium, cerium, etc.; in one case[582] the rare earth metals, alloyed with barium, silicon, uranium, or titanium, are to be used with ‘an oxidising agent which leaves a non-volatile residue.’ None of these mixtures appears to have been successful.
[581] Vide, e.g. E. 14692, 1908; D. R. P. 158215.
[582] F. 403722, October, 1909.
Cerium compounds have also been proposed for use in arc-lamp electrodes; it is claimed that they give a very intense light, one patent[583] adding that the presence of cerium peroxide and a little fluorspar causes the arc to burn evenly and quietly. In another, the use of a mixture of tungstates or molybdates of the alkaline earths, with fluorides of the rare earth elements is protected;[584] the use of pyrophoric alloys, either entirely, or for the core of the electrode, has also been suggested.[585]
[583] E. 414707, June, 1910.
[584] F. 431040, August, 1911; also E. 21374, 1909.