438 Hess and Wells — Occurrence of Struverite. 



1 2 



H 2 0-4 0-4 



Si0 2 1-8 1-8 



Ti0 2 45-8 45-8 



Sn0 2 1-3 1-3 



FeO 7-5 7-5 



Ta 2 6 376 30-5 



Cb„0 6 (by difference) 5-6 12-7 



Although these results give a fair idea of the composition, 

 it was concluded that a separation of the chlorides by fractional 

 distillation might be a more advantageous method of analysis. 

 The separation of titanium from columbium and tantalum in 

 this way was suggested by a method of separating titanium 

 and iron occasionally employed in steel analysis,* although, of 

 course, the quantities are not exactly comparable. 



Experiments were first made on known quantities of TiO, and 

 Cb 2 6 using sugar carbon and dry chlorine to produce the 

 chloride in a hot, hard, glass tube, and it was found that an 

 approximate separation could be made. 



A mixture of titanium, columbium and tantalum oxides, 

 obtained from the mineral under examination, and free from 

 other elements, was subjected to treatments with carbon in 

 chlorine. 



Taken 0-2248 g. Found TiO,. 0-1345 g. 



(Ta,Cb) 2 6 0-0789 



Total found 0-2134 g. 



Deficit -0114 g. 



Applying the ratio of Ti to (Ta,Cb) here found to 89 - l per 

 cent of the mineral (the total acid earths) gives Ti0 2 56 - 2, 

 (Ta,Cb) 2 5 32-9 per cent. This is considerably more Ti0 2 

 than found by the colorimetric method. 



Owing to the difficulty of completely converting the oxides 

 into chlorides by the use of carbon, the apparatus was some- 

 what modified and chloride of sulphur tried instead. It was 

 found possible to convert nearly half of a gram of a mixture 

 consisting of the oxides of titanium, tantalum or columbium 

 into chlorides in two hours. A porcelain boat was used in a 

 long, hard, glass tube. That portion of the tube used for the 

 condensation of the less volatile chlorides was warmed uni- 

 formly by a jacket of asbestos containing electrical resistance 

 wire. Sufficient chloride of sulphur was introduced as vapor 

 by merely passing the chlorine through a distilling flask in 

 which sulphur chloride was kept gently warmed. Practically 



* Blair, The Chemical Analysis of Iron, 6th ed. , p. 74. 



