282 SMITHSONIAX MISCELLANEOUS COLLECTIOXS VOL. 54 



.0173 



Hence Ti = 49.894. 



It will be seen that the first three of these results agree well with each 

 other and are much liigher than the remaining six. The last four ex- 

 periments were made purposely with tubes which had been previously 

 opened, in order to determine the cause of the discrepancy. According 

 to Pierre, the opening of a tube of titanium cliloride admits a trace of 

 atmospheric moisture. This causes a deposit of titanic acid near the 

 mouth of the tube, and liberates hydrochloric acid. The latter gas being 

 heavy, a part of it falls back into the tube, so that the remaining chloride 

 is richer in chlorine and poorer in titanium than it should be. Hence, 

 upon titration, too low figures for the atomic weight of titanium are 

 obtained. Pierre accordingly rejects all but the first three of the above 

 estimations. These give Ti = 50.265. 



The memoir of Pierre upon the atomic weight of titanium was soon 

 followed by a paper from Demoly,^ who obtained much higher results. 

 He also began with titanic chloride, which was prepared from rutile. 

 The latter substance was found to contain 1.8 per cent, of silica; whence 

 Demoly inferred that the TiCl^ investigated by Eose and by Pierre might 

 have been contaminated with SiCl^, an impurity which would lower the 

 value deduced for the atomic weight under consideration. Accordingly, 

 in order to eliminate all such possible impurities, this process was resorted 

 to : the chloride, after rectification over mercury and potassium, was 

 acted upon by dry ammonia, whereuix)n the compound TiCl4.4XH3 was 

 deposited as a white powder. This was ignited in dry ammonia gas, and 

 the residue, by means of chlorine, was reconverted into titanic chloride, 

 which was again repeatedly rectified over mercury, potassium and potas- 

 sium amalgam. The product boiled steadily at 135°. This chloride, 

 after weighing in a glass bulb, was decomposed by water, the titanic acid 

 was precipitated by ammonia, and the elilorine was estimated in the 



' Ann. Chem. Pharm., 72, 214. 1849. 



