ATOMIC WEIGHTS 145 



The determinations of Dittmar ' resemble those of Diehl ; but the 

 lithium carbonate used was dehydrated by fusion in an atmosphere of 

 carbon dioxide. The carbonate was treated with sulphuric acid, and 

 the CO2 was collected and weighed in an absorption apparatus, which 

 was tared by a similar apparatus after the method of Regnault. The 

 following percentages of CO2 in Li^COg were found : 



59.601 



59.645 



59.529— rejected 



59.655 ' 



59.683 



59.604 



59.517 



59.663 



60.143 — rejected 



59.794 



59.584 



Mean of all, 59.674 



Rejecting the two experiments whicli Dittmar regards as untrust- 

 worthy, the mean of the remaining nine becomes 59.638, ±.0173, and 

 Li=: 6.891. This combines with the work of Diehl and Troost, as follows : 



Dlehl 59.417, ± .0060 



Troost 59.456, ± .0200 



Dittmar 59.638, ± .0173 



General mean 59.442, ± .0054 



The unique merit of the determinations by Richards and Willard " is, 

 not only that their work was done with scrupulous accuracy, but that 

 their ratios give simultaneous values for the atomic weights of lithium, 

 silver and chlorine, which are independent of all other data. Analyses 

 of lithium perchlorate gave directly the molecular weight of lithium 

 chloride, with reference to oxygen alone, and with that their other ratios 

 are reducible. The data for the perchlorate are as follows, with vacuum 

 weights : 



Preliminary Series. 



' Trans. Roy. Soc. Edinburgh, 35, H, 429. 

 ^ Journ. Amer. Chem. Soc. , .32, 4. 1910. 



