278 THE ATOMIC WEIGHTS. 



in which one gramme of the fluoride yielded from 1.734 to 1.737 of sul- 

 phate. At first he regarded these as accurate, but he soon found that 

 particles of spar had been coated with sulphate, and had therefore 

 escaped action. In the following series this source of error was guarded 

 against. 



Starting with fluor spar, Louyet found of sulphate as follows: 



1.742 



1-744 



1.745 



1.744 



1-7435 



I •7435 



Mean, 1.74.37, ± .0003 



A second series, upon artificial fluoride, gave : 



1-743 

 1. 741 

 1. 741 



Mean, 1.7417, zb .0004 



Dumas * published but one result for calcium fluoride. .495 grm. gave 

 .864 grm. sulphate, the ratio being 1 : 1.7455. 



De Lucaf worked with a very pure fluor spar, and jniblished the fol- 

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

 given in the third column : 



.9305 grm. CaF, gave 1. 630 grm. CaSO^. I.75l8 



-836 " 1.459 " 1.7452 



-502 " .8755 " 1.7440 



•3985 " -6945 " 1.7428 



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

 1.7459, ± .0011. 



MoissanJ unfortunately gives no details 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 

 I. 7410 



Mean, 1.7427 



*Ann. Cheni. Pharni., 113, 28. 1S60. 

 + Conipt. Rend., 51, 299. i860. 

 I Compt. Rend , iii, 570. 1890. 



