TITANIUM. 191 



These figures, with = 15.879, give values for Ti ranging from 46.03 

 to 47.98; or, in mean, Ti^ 46.80. The}^ are not, however, sufficiently 

 explicit to deserve any farther consideration. 



In 1847 Isidpr Pierre made public a series of important determina- 

 tions.* Titanium chloride, free from silicon and from iron, was ])re- 

 pared l\v the action of chlorine upon a mixture of carbon with pure, 

 artificial titanic acid. This chloride was weighed in sealed tubes, these 

 were broken under water, and the resulting hydrochloric acid was titrated 

 with a standard solution of silver after the method of Pelouze. I subjoin 

 Pierre's weighings, and add, in a third column, the ratio of TiCl^ to 100 

 23arts of silver : 



TiCL. Ao-. Ratio. 



Mean, 44.432, — .0173 



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

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

 periments were made purjjosely with tubes which had been previously 

 opened, in order to determine the cause of the discrepanc^^ According 

 to Pierre, the opening of a tube of titanium chloride 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 beino- 

 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. 



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

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

 He also started out from 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 Rose and by Pierre might 

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

 value deduced for the atomic weight under consideration. According! v, 

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



*Ann. Chira. Phys. (3), 20, 257. 



■f Ann. Chem. Pharm., 72, 214. 1849. 



