the Periodic Law of the Chemical Elements. 103 



a number which is very nearly identical with 6*64, which was 



A 



obtained as the value of cby applying the equation c = 

 to all the atomic weights, as in Table I. 



m-\~ V 



If there be any truth in the above, then the atomic weights 

 at present accepted for cassiuni (132' 6) and copper (63*3) are 

 rather too high, and that for gold (196'9) somewhat too low. 

 Caesium should be about 131, copper about 62, and gold 

 about 198. 



In Table II. (pp. 104, 105) is given a list of the atomic weights 

 calculated from the equation A=c(m-\- ^ v\ c being taken 

 equal to 6* 6. 



The Table shows that, of the 54 elements considered, the 

 difference between the calculated and experimental atomic 

 weights 



f in the case of 21 elements is less than 1 unit ~ 



[ „ „ 12 „ it lies between 1 & 1| units 

 f ,* ,, 8 „ „ „ 2 & 3 



33 



21 



55 



55 





55 



55 



55 



8 



55 



5? 



55 



3 



55 



55 



55 



6 



55 



>5 



55 



4 



55 



3&3± 

 4&4| 

 6&6£ 



Mean 

 ' + 1-9 



V^ >5 55 * 55 55 55 w v*/ \J ^ 



The considerable difference between the calculated and ex- 

 perimental values in some cases shows that the expression 

 At. wt. = 6*6 (m+ s/ v) is at best only approximate. The 

 atomic weights calculated by it are, however, very much 

 nearer the experimental values than those calculated accord- 

 ing to Dulong and Petit's law from the equation 



. , , _ atomic heat 6*4 



~ specific heat "" spec, ht.' 



Thus of the 44 elements * of which the specific heats have 

 been directly determined, the difference between the calculated 

 and experimental atomic weights 



in the case of 9 elements is less than 1 unit 



»( 



r 



23<< 



55 



5 



55 



it lies between 1 & 1 \ units 



55 



2 



55 



55 



„ 1J&2 „ 



55 



5 



55 



55 



„ 2 &3 „ 



55 



5 



55 



55 



5, 3 &4 „ 



55 



4 



55 



55 



„ 4 &5 „ 



55 



2 



55 



55 



55 5 & 6 „ 



55 



5 



55 



55 



„ 6 &7 „ 



55 



2 

 5 



55 



55 



55 

 55 



„ 7 &10 „ 

 „ 10 & 15 „ 



Mean 



+ 4-2 



* Exclusive of C, Si, B, N, 0, F, and H, which are apparently such 

 marked exceptions to Dulong' and Tetit's law. 



