igos .] HALL AND SMITH— COLUMBIUM. 203 



chloride. Therefore, care should be taken in the dehydration of 

 the tetrachloride used ; otherwise the product will be contaminated 

 with oxide. This seems to be the best method for the preparation 

 of tantalum chloride in large quantities and in a high state of 

 purity. The chloride is an excellent starting-out material for a re- 

 determination of the atomic weight of tantalum, a number none 

 too definite, as a study of the series of results obtained by Marignac 

 (Zei/. anal. Chem., 5, 478) by the analysis of potassium tantalum 

 fluoride and ammonium tantalum fluoride will show. 



The action of carbon tetrachoride on the oxide of columbium 

 also affords an excellent method for the preparation of the oxy- 

 chloride of that element. It is produced, however, in a very 

 voluminous state, and mats together to a tough felt, completely 

 stopping up any tube used in its preparation. When heated in a 

 sealed tube it condenses on a warm surface to very compact lus- 

 trous silky needles. It is very difficult to remove the last traces of 

 columbium pentachloride from this body. This may be done, 

 however, by subliming it in a current of chlorine over ignited 

 oxide, but as long as any carbon tetrachloride is present the colum- 

 bium chloride will continue to be formed. To make the chloride 

 of columbium it is necessary to have recourse to the action of sul- 

 phur monochloride on the oxide or to act on the oxide with carbon 

 tetrachloride in a sealed tube. 



PROPERTIES OF COLUMBIUM CHLORIDE. 



As already mentioned, columbium chloride is soluble in carbon 

 tetrachloride, forming a yellow colored solution. It is much more 

 soluble when hot than when cold and crystallizes out on cooling in 

 well defined crystals. It is also soluble in sulphur monochloride, 

 the solution saturated in the hot being red in color and depositing 

 yellow crystals of the chloride on cooling. It dissolves in ether 

 with a yellow color. On evaporating this solution on a water bath 

 a thick liquid remains, and an acid vapor is given off, but no crys- 

 tals separate. Upon ignition the mass chars, then burns and leaves 

 a residue of oxide. On passing dry ammonia gas into the ethereal 

 solution of the chloride a heavy precipitate is formed. This is am- 

 monium chloride and columbium nitride. On washing with water 

 the ammonium chloride is dissolved out, leaving a white residue 

 which reverts on ignition to oxide of columbium, and when boiled 



PROC. AMER. PHILOS. SOC. XLIV. l8o. M. PRINTED AUGUST I, I905 



