OCTOBEB 23, 1908] 



SCIENCE 



551 



salts, and to Weiss 's application of 

 "misch metal," a mixture largely of the 

 cerium earth metals, to the reduction of 

 the oxides of Mo, V, Nb and Ta. Since 

 cerium is obtained in large quantities as a 

 by-product in the preparation of thorium 

 salts from monazite, its various applica- 

 tions are of special interest. 



Of the elements gallium, indium and 

 thallium little will be said. During the 

 past five years, gallium has been mentioned 

 but once in the Zentralblatt, and that on 

 account of its occurrence in a Sardinian 

 blend. Renz and Thiel abroad and 

 Mather in this country have done interest- 

 ing work upon the properties and salts of 

 indium. Indexes to the literature of these 

 two elements, by Browning, were pub- 

 lished by the Smithsonian Institution in 

 1904 and 1905. Thallium, with its two dis- 

 tinct conditions of oxidation and its ease 

 of detection by means of its characteristic 

 flame spectrum, has offered an attractive 

 field to the student of pure chemistry. 

 Growing interest in it is indicated by an 

 increase of 200 per cent, in the number of 

 reviews dealing with that element in the 

 Zentralblatt for 1907 as compared with 

 1903. 



Passing to group (4) we find besides 

 thorium and cerium, already mentioned, 

 the elements titanium and germanium. 

 Germanium, like gallium, seems to have 

 attracted little attention of late. An in- 

 dex to the literature of germanium, by 

 Browning, was published in 1904 by the 

 Smithsonian Institution. 



Titanium can not be regarded as of rare 

 occurrence, but I think that most chem- 

 ists will allow it to be classed as a rare 

 element under our definition. Hillebrand 

 states that as far as his personal experi- 

 ence goes, titanium is entirely absent 

 from no igneous, metamorphic, or sedi- 

 mentary rock of a more or less siliceous 

 character, and Clarke tells us that of 



800 igneous rocks analyzed in the labora- 

 tory of the Geological Survey, 784 con- 

 tained titanium. The element is now gen- 

 erally considered to stand tenth in order of 

 abundance in the earth's crust as far as that 

 has been explored, being more abundant 

 than copper, lead or zinc. Considering these 

 facts it is with satisfaction that we find 

 titanium gradually taking its place among 

 the useful elements. Until quite recently 

 the presence of one per cent, or more of 

 titanium in iron ores was considered suffi- 

 cient to make them undesirable on account 

 of the formation of pasty slags in the 

 metallurgical process. This difficulty, ac- 

 cording to Rossi,* can be avoided by judi- 

 cious regulation of fluxes and tempera- 

 tures. The addition of titanium to 

 cast iron has been shown to increase its 

 strength, and the presence of the same 

 element in steel seems not only to augment 

 the tensile strength of the steel but also 

 to raise its limit of elasticity. This prop- 

 erty of titanium has developed the pro- 

 duction of ferro-titanium for use in the 

 manufacture of steel. 



According to the last volume of the 

 "Mineral Resources," titanium is being 

 used to a certain extent as a filament for 

 incandescent electric lamps, and has the 

 advantage over tungsten of a higher 

 melting point and higher electrical re- 

 sistance. Rutile, titaniferous magnetite, 

 and titanium carbide are all finding some 

 use as electrodes with carbon blocks in arc 

 lamps. Other commercial uses of titan- 

 ium are found in the employment of rutile 

 for giving porcelain tile a yellow color and 

 for coloring artificial teeth; of titanous 

 chloride and titanous sulphate as mor- 

 dants and of titanous potassium oxalate 

 as a mordant and yellow dye in the treat- 

 ment of leather. Recently we have seen 

 quite frequent references to the applica- 



*Eossi, A. J., Trans. Am. Inst. Min. Eng., Vol. 

 XXI., 832. 



