102 ABSOLUTE ATOMIC WEIGHT. 



Dumas and Stas^ 1840 : 



5.40 gr., 5 Det., Extr. 95 28; 67. Mean 2 low c 

 .Erdtnann and Marchand^ 1841 : 



4.83 gr., 5 Det., Extr. 73 96; 77. Mean 30 low. 

 Roscoe, 1883: 



6.03 gr.. 5 Det., Extr. 75 49526. Mean 5 low. 

 Friede^ 1884: 



1.33 gr., 2 Det., Extr. 40 28; 12. Mean 33 low. 

 Mean of first 3 sets of 5 det. each, 12 low. 



Total weight of diamond burnt 16.26 grammes in these 

 15 determinations, averaging 1.08 grammes in each. 



The four series of determinations divide sharply into 

 two groups, according to the amount of the analytical 

 excesses. To obtain the corresponding effect on the atomic 

 weight, we must remember that a rise of o.i corresponds to 

 220 low in the fourth place. 



Hence Dumas mean, 2 low, corresponds to 12.001 ; that 

 of Roscoe to 12.0025. 



The second group, giving an analytical excess of about 

 " 30 low " corresponds to about 12.017. 



Since Dumas and Roscoe used over n grammes of 

 diamond against the others only about half as much, it is 

 evident that the former had the best chance of getting 

 accurate results. 



It will be noted, that Friedel had only about half a 

 gramme for each determination, while all the others averaged 

 a gramme for each determination. 



We must conclude that the atomic weight of carbon 

 (diamond) is 12 exactly, within the limit of the errors of 

 the experiment. 



This limit is o.ooi in the case of Dumas, 0.002 in the 

 case of Roscoe, and 0.017 in the case of Erdmann and 

 Marchand, and for Friedel also. 



This is the simple record of the facts ascertained. It is 

 most admirable. 



A False Correction. 



Recently A. Scott has called attention to the effect of the 

 absorption of carbon dioxide on the volume of the saturated 



