176 COL UM BITE. 



bright copper-turnings; the neck of the retort is 

 drawn out to a point, which is bent downwards. When 

 the bichloride of titanium has been left for some time 

 in contact with the metal, it is distilled off by gentle 

 ebullition, and immediately received in tubes, which 

 are afterwards hermetically sealed. 



In order to prepare pure titanic acid from the 

 bichloride, it is gradually mixed with water, avoiding 

 all rise of temperature, which would render the 

 solution turbid, and the titanic acid precipitated by 

 ammonia. 



Pure ignited titanic acid is white, frequently with a 

 tinge of yellow. During ignition it has a lemon- 

 yellow color. When exposed to a very high degree 

 of heat it becomes brownish. It is then perfectly 

 insoluble in hydrochloric acid. By long digestion 

 with concentrated sulphuric acid, it is dissolved. 



94. COLUMBITE. (NIOBITE.)* 

 (FeO,MnO)(Cb0 5 Ta0 5 .) 



The mineral is not decomposed by acids. It is best 

 decomposed by fusing it in the form of a levigated 

 powder, with 6 parts of bisulphate of potassa, in a 

 platinum crucible. The salt is first fused by itself, 

 allowed to solidify, the powdered mineral thrown upon 

 it, and the two gradually fused together. The fusion 

 is continued until the mineral has entirely dissolved. 



The mass is afterwards repeatedly boiled with 

 water, and the undissolved hydrated acids filtered off 

 and washed. It still contians sesquioxide of iron, and 

 commonly also a small quantity of binoxide of tin and 

 tungstic acid. 



* Sp. gr. = 5.4 to 6.39. Often contains small quantities of Sn0 2 , 

 WO, and CaO. 



