TITAMUM. 211 



Upon comparing Demoly's figures with those obtained by 

 Rose, certain points of similarity are plainly to be noted. 

 Both sets of results were reached by essentially the same 

 method ; and in both the discordance between the percent- 

 ages of titanic acid and of silver chloride is glaring. This 

 discordance can rationally be accounted for by assuming 

 that the titanic chloride was in neither case absolutely 

 what it purported to be ; that, in brief, it must have con- 

 tained impurities; such for example as hydrochloric acid, 

 as shown in the experiments of Pierre, or possibly traces of 

 oxychlorides. Considerations of this kind also throw doubt 

 upon the results attained by Pierre, for he neglected the 

 direct estimation of the titanic acid altogether, thus leaving 

 us without means for correctly judging as to the character 

 of his material. In fact, not one of the determinations oi 

 the atomic weight of titanium can be regarded as trust- 

 Avorthy. All depend upon the chloride, and the volatile 

 chlorides of metals are as a class especially liable to con- 

 taminations of a kind most difficult to recognize. Possibly 

 a series of good determinations might be based upon analy- 

 ses of some of the titanofiuorides. I subjoin a combination 

 of the foregoing mean values, feeling that such a general 

 average is a little better than any one set of determinations 

 taken singly : 



From Rose's analyses Ti = 48.710, dr .105 



" Pierre's " " ^49.889,^.096 



" Demoly's " " =52.191,^.153 



General mean " = 49.846, ± .064 



Or, if = 16, Ti = 49.961. 



This mean agrees with the average of all of Pierre's ex- 

 periments. 



