ATOMIC AVEIGHTS 405 



A second series, upon artificial fluoride, gave : 



1.743 

 1.741 

 1.741 



Mean, 1.7417, ± .0004 



Hence F= 19.03. 



Dumas ^ published but one result for calcium fluoride. .495 ^rra. gave 

 .864 grm. sulphate, the ratio being 1: 1.7455. Hence P=: 18.95. 



De Luca " worked with a very pure fluor spar, and published the fol- 

 lowing results. The ratio between CaS04 and one gramme of CaF, is 

 given in the third column : 



.9305 grm. CaF„ gave 1.630 grm. CaSO^. 1.7518 



.836 " 1.459 " 1.7452 



.502 " .8755 " 1.7440 



.3985 " .6945 " 1.7428 



Hence F = 18.97. 



If we include Dumas' single result with these, we get a mean of 

 1.7459, ±.0011. 



Moissan^ unfortunately gives no detail? nor weighings, but merely 

 states that four experiments with calcium fluoride gave values for F rang- 

 ing from 19.02 to 19.08. To S he assigned the value 32.074, and probably 

 Ca was taken as = 40. With these data his extreme values as given may 

 be calculated back into uniformity with the *ratio as stated above, 

 becoming — 



1.7444 

 1.7410 



Mean, 1.7427 



Hence F= 19.011. 



If we assign this equal weight witli Berzelius' series, the data for this 

 ratio combine thus: 



Berzelius 1.7500, ± .0004 



Louyet, first series 1.7437, ± .0003 



Louyet, second series 1.7417, ±: .0004 



De Luca with Dumas 1.7459, ± .0011 



Moissan 1.7427, ± .0004 



General mean 1.7444, ± .00018 



1 Ann. Chem. Pharm., 113, 28. 1860. 

 = Compt. Rend., 51, 299. 1860. 

 sCompt. Rend., m, 570. 1890. 



