226 ARSENIC. 



This is absolutely nearer, than Mallet's result, and on 

 both sides of the true atomic value. By the way, Berzelius 

 found 27.2 by this method. 



But the chemical condition of the sulphate is rather 

 improper not crystalized. 



While there is no doubt but 27 is the true atomic weight, 

 new determinations are urgently called for, provided good 

 methods are used. 



Other Determinations have been made in considerable 

 number. The most pretentious are those by Mallet, Phil. 

 Transact, 1880, p. 1003. 



Most of these determinations of Mallet are made accord- 

 ing to Stasian methods, hence useless; the only exception is 

 the case above used, but that was very much neglected bj 

 him. The use of hydrogen is out of the question, since 

 other Stasians have thoroughly discredited it. 



Dumas, in 1858, used the chloride, and Mallet, in 1880, 

 the bromide; both determined by silver. 



Such methods are useless for a metal like aluminum. 

 They sin too greatly against the first part of the old rule of 

 Berzelius; for they depend mainly on the "skill" of the 

 chemist, not on the fixed conditions of the substance or the 

 process, not on nature. See p. 3. 



Chemical acrobats are no longer in demand. True At. 

 Weights, p. 135. 



As = 75. ARSENIC. EDGAR F. SMITH. 



The most reliable work on the atomic weight of arsenic 

 has been done at the suggestion and under the direction of 

 Professor Edgar F. Smith in the John Harrison Laboratory 

 of the University of Pensylvania. 



The work itself has been executed by J. G. Hibbs in that 

 laboratory; but we all know that the method and direction 

 is the main thing. 



Pyroarsenate moderately heated in a current of dry muri- 

 atic acid gas leaves a residue of salt. Hence the atomic 

 ratio is 

 4 Na Cl : Na4 Ov As2 = 234 : 354 = 0.66 102. Change 38 low. 



