1889.] Revision of the Atomic Weight of Gold. 



73 





Atomic weight of gold. 



Average value 

 from 

 aggregate 

 weights. 



T 1 



.Lowest value 

 from a 

 single 



experiment. 



Jiignest value 



11 U 111 Cb 



experiment. 



First series 



(5 experiments) .... 



196 '722 



196 -688 



196 -770 



Second „ 



(6 



j, ) . . . . 



196 -790 



196*731 



196 -843 



Third „ 



(4 



) . . . . 



196-775 



196-685 



196 -817 



Fourth „ 



(5 



» ) • • • • 



197 -225 



197*131 



197 -289 



Fifth „ 



(5 



)) ) • • • • 



196 -823 



196 -709 



196 -945 



Sixth „ 



(3 





197-137 



196-994 



197-283 



Seventh „ 



(6 



) . • . . 



196-897 



196 -848 



196 -956 



If the general mean be taken of the results of all these series of 

 experiments, nsing the average valne derived from each, and giving 

 all an equal weight, the number 196"910 is obtained for the atomic 

 weight of gold. 



But reasons are given for feeling much less confidence* in the 

 results of the fifth and sixth, series of experiments (made by electro- 

 lysis) than in the rest ; if these two series be excluded the general 

 mean becomes 196-882. 



A certain degree of suspicion as to possible constant error having 

 been shown to perhaps affect the results of the fourth series, if this also 

 be left out, and only the first three and the seventh series be considered, 

 the general mean will be 196" 796. 



And finally, if, for the sake of comparison with the results of the 

 recent researches of other chemists, only the first three series be 

 included, in which auric chloride and bromide were examined, the 

 general mean will be 196*762 — a result rather higher than that of 

 Kriiss and lower than that of Thorpe and Laurie, but nearer to the 

 latter than the former. 



In conclusion, reference is made to the bearing of the results 

 reached on Mendelejeffi's periodic classification of the elements, and 

 on the hypothesis of Prout, and attention is drawn to the desirability 

 of a general re- examination of atomic weights, not by a single method 

 only in each case, or by methods more or less nearly similar or 

 dependent on each other, resting satisfied with a close agreement of 

 results under these conditions, but by as many distinct and indepen- 

 dent methods as may be possible for each element examined. 



