CALCIUM. 71 



2.738 gmi. CaCl^ = 5.309 grm. Ag. 51-573 



2.436 " 4.731 " 51-490 



1.859 " 3.617 " 51.396 



2.771 " 5.38.85 " 51-424 



2,240 " 4-3585 " 51-394 



Mean, 51.4554, ± .0230 



We have now four ratios to calculate from, as follows : 



(I.) Per cent, of CaO in CaCOj, 56.0198, =!= .0029 



(2.) CaO : SO3 : : loO : 142.3998, dr .051S 



(3.) CaCOg : CaSO^ : : 100 : 136.0525, :±: .0071 



(4.) Ag : CaCl.^ : : 100 : 51.4554, =t .0230 



These give us the subjoined values for calcium : 



From (I) Ca = 39.955, ± .011 



From (2) " ^40.139, zb .023 



From (3) " = 39.925, zh .068 



From (4) " = 40.069, zb .058 



General mean " = 39.990, ± .010 



If = 16, then Ca = 40.082. 



A glance at the above figures will show that, if, as is 

 probable, the value deduced from the composition of calcium 

 carbonate is a trifle too high, the general mean must be too 

 high also. It is, therefore, interesting to see what result the 

 very latest of Erdmann and Marchand's experiments will 

 lead to. They found, after taking every precaution, in a 

 single exjDeriment that calcium carbonate yielded 55.998 per 

 cent, of lime. From this we get Ca = 39.905 ; or, if = 

 16, Ca = 39.997. It is possible, then, that " Front's law " 

 may hold good for calcium. 



