570 MINERALOGY 



bead in the O. F. until all the particles have dissolved, then in the 

 R. F. "for considerable time, when it will be a light violet when cold. 

 In the treatment with tin, the bead is removed from the wire and 

 placed in a shallow cavity beside a piece of tin of about half its 

 size, then fused in the R. F. for some time ; the tin and S. Ph. beads 

 will fuse, but remain distinct, simply sticking to each other and 

 rolling around in contact during the fusion. The fused tin oxi- 

 dizes at the expense of the oxygen combined with the titanium, 

 which is reduced to Ti 2 O 3 , coloring the bead violet when cold. 



b. Wet test. Insoluble substances are finely powdered, made 

 into a stiff paste with water and 6 parts soda and a little borax, 

 and thoroughly fused either on coal or platinum foil. The fusion is 

 dissolved in 2 cc. of concentrated HC1. Titanium is now present 

 in solution as Ti0 2 ; if much iron is present, the solution will be 

 yellow from the ferric chloride. Granulated tin is now added, which 

 dissolves in the HC1, forming stannous chloride, SnCl 2) and liberates 

 hydrogen. As the hydrogen reduces the ferric chloride to ferrous 

 chloride the yellow color due to iron disappears, then the TiO 2 is 

 reduced to Ti 2 O 3 , and the solution assumes a violet color, especially 

 on standing. 



c. Hydrogen peroxide test. If the amount of titanium present 

 is less than 3 per cent., the above tests are not sufficiently delicate. 

 The substance is fused as directed above, but is dissolved in 3 cc. 

 dilute H 2 SC>4 by boiling in a test tube ; when dissolved, dilute with 

 water to 10 cc. and add 2 cc. of hydrogen peroxide solution, when 

 if titanium is present the solution will assume a golden yellow and if 

 much is present an orange color. 



Illustration. Use powdered rutile and proceed with the tests 

 as directed. 



Columbium (Niobium) Cb(Nb). Atomic weight, 93.5. Fusing 

 point, 1950 C. 



a. Wet test. Columbium compounds are very insoluble in 

 acids, and must be thoroughly fused with borax or potassium 

 bisulphate on wire or foil ; the fusion is then dissolved in con- 

 centrated HC1 as in the case of titanium, when granular zinc is 

 added and the solution is reduced in the same way. If columbium 

 is present, it will become blue. In the reduction if titanium is 

 present also, the solution will be violet first, as titanium is the first 

 to reduce ; then the columbium will be reduced, and the solution will 

 be finally blue. Tungsten is another metal which yields blue solu- 

 tions after reduction with tin ; for distinguishing tests see b, p. 587. 



