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XXIII. On some Atomic Weights. By Edward Turner, 

 M.D. F.R.S. Lojid. Sj- Ed., Sec. G.S., Professor of Chemistry 

 in the University of London.* ■' '^ uj lu j.' //^ 



': 'R / emsa' 9ifi f{,t(V3- 



T^HE adoption by British chemists of the opinion that atomic 

 -*■ weights are multiples by whole numbers of the atomic 

 weight of hydrogen, and the experimental contradiction given 

 to that opinion by so distinguished an analyst as Berzelius, 

 induced me about three years ago to undertake an inquiry 

 into the subject. As nearly the sole evidence in proof of the 

 multiple theory is embodied in the First Principles of Che- 

 mistry, published by Dr. Thomson, I turned to that work with 

 the view of putting some of the statements, contained in it, to 

 the test of careful experiment. 1 commenced with investiga- 

 ting the composition of the chloride of barium, because Dr. 

 Thomson had employed it as a means of obtaining a con- 

 siderable number of his results. My inquiry, published in the 

 Philosophical Transactions for 1829f, proved the existence of 

 a material error ; and Dr. Thomson has since acknowledged 

 it by changing the equivalent of barium from 70 to 68 J. It is 

 obvious that this error vitiates many of his other equivalents; 

 and that as so great a mistake has been committed in a fun- 

 damental question, an inquiry into the accuracy of minor points 

 is superfluous. 



I apprehend, therefore, that the atomic weights at present 

 employed by British chemists are unsupported by satisfactory 

 experiments, and that those who adopt the multiple theory 

 cannot adduce exact analyses in defence of the practice. With 

 this feeling I have occupied my leisure for some time past in 

 examining the equivalents of several important substances, 

 endeavouring to ascertain the value of the numbers adopted 

 in this country compared with those of Berzelius. I shall 

 confine myself entirely to results, partly because some of 

 the points are not yet settled to my satisfaction, and partly 

 because I hope early in the ensuing winter to lay the details 

 in a more perfect form before the Royal Society. 



Lead. — The equivalent of lead is frequently employed as 

 the basis of calculation in chemistry. The number adopted 

 in this country, on the authority of Dr. Thomson, is 104. 

 Berzelius has lately repeated his earlier experiments on the 



• Read before the Chemical Section of the British Association at Oxford, 

 June 27, 18."J2; and coinmiinicated by the Author. 



+ Dr. Turner's paper " On the Composition of Chloride of liarium,''' will 

 be found in Phil. M;ig. and Annals, N.S. vol. viii. p. 180. — Edit. 



t Dr. 'riioiusoii's correction will be found in Phil. Mag. and Annals, 

 N.S. vol. X. p. 3'J2.— Edit. 



