164 Mr, Prideaux on the mean Atomic Weights 



instead of 3 ; and boron 2*95—2 = '95 ; which would lie be- 

 tween the numbers of these two eminent chemists ; between 

 the result of Berzelius's analysis of borate of ammonia, and 

 Thomson's of borax ; and between the analysis of the hydrate, 

 in which they exactly accord, and that of Davy. All these 

 experiments may be referred to (First Prin., article Boron). 



\e.) Chlorine. — Although Berzelius's method of taking the 

 undecompounded gases, hydrogen, azote, &c. in volumes, 

 instead of equivalents, be somewhat incommodious, it was 

 necessary, in giving his numbers, to conform to it ; and the 

 fractional expression is employed as readiest of comparison 

 by neglecting the denominator. 



It may be here observed, that direct experimental compa- 

 rison of the atomic weights of chlorine and oxygen, by heat- 

 ing chlorate of potash very gradually in a platinum crucible 

 over a spirit-lamp, before I recollected the experiments of 

 Berzelius (Ann. Phil. xv. 91), gave me a number for chlorine 

 rather less than his ; although indirect trials, by double de- 

 composition, gave a number nearly corresponding with that 

 of Thomson. 



(f.) Cobalt. — The number for this metal being calculated 

 by Berzelius from experiments not his own, it seemed fair 

 to incline the mean to Thomson's side. 



(g.) Columbium. — This number being also altered, without 

 stated reasons, in Berzelius's last table, and two-thirds of it, 

 (indicated by his construction of the acid Cb 2 ) = 769'14-3, dif- 

 fering widely from Thomson's, even if doubled ; these seemed 

 no sufficient indications for altering the latter. 



(h.) Fluoron (and Fluorine). — If the fluoric be an oxy-acid, 

 its base must have a name; and the above is used as the 

 readiest that occurs. 



Berzelius found (Ann. Phil. xv. 280) that fluate of silver, 

 " heated to redness, melted, and continued, as long as it was 

 exposed to the fire, to give out fluoric acid and oxygen gases ; 

 whilst metallic silver was disengaged :" and he believed this 

 was not owing to the presence of water. Even if it had been 

 from that cause, it would be remarkable that so energetic a 

 substance as the hypothetical fluorine should be so easily 

 driven off; when iodine, under similar circumstances, bears 

 a red heat. Fluoboric acid is explained on the fluorine hypo- 

 thesis (First Prin. ii. 183), as " 1 atom fluorine and 2 atoms 

 boron;" although (at vol. i. 161) it is said "Davy's experi- 

 ments on the composition of boracic acid ; Berzelius's ana- 

 lysis of borate of ammonia, and mine of borax ; — preclude the 

 possibility of either more or less than an atom of boracic acid 

 being united, in fluoboric acid, with an atom of fluoric acid." 



There 



