36 THE ERRORS OF PRECISION*. 



The atomic weight in reference to nitrogen is given, and 

 this atomic weight of nitrogen "is taken at 14.04." 



The atomic weight of uranium stated ranges from 239 .3 

 to 239.6 occuring each once. Two determinations gave 

 239.5 and four g ave 2 39-4- Eight determinations were made. 



Accordingly, the analytical ratio Ur : N ranged 17.044 

 to 17.066. 



But if instead of taking the atomic weight of nitrogen as 

 14.04 it were taken at 14 exactly, the above ratios multiplied 

 by 14 would give for uranium values ranging from 238.6 to 

 238.9, which are 0.7 lower than the values reported by 

 A. Gautier on the assumption that N is 14.04. 



Here we have a change of seven tenths of a unit in the 

 atomic weight of uranium consequent upon the slight 

 change of the atomic weight of nitrogen from 14.04 to 14, 

 amounting to four hundreths only. 



All previous determinations make it highly probable that 

 Ur is 240. Gautier reports 239.4 for N = 14.04; for N = 14 

 it would come down to 238 .7. 



This shows strikingly the great importance of the values 

 of the auxiliary atomic weights used in the calculations 

 of the chemical experiments made, that is, in the so-called 

 reduction of the work. 



The very considerable change or uncertainty also empha- 

 sizes the necessity of giving the original data of the deter- 

 minations, the direct weighings (reduced to vacuum only), 

 so that the chemical work done may be used and not have 

 to be thrown away. 



We shall find, in a subsequent part of this work, that the 

 real atomic weight of nitrogen is 14 exactly and not 14.04. 

 The weighings of Lord Rayleigh have made the Stasian 

 value 14.04 absolutely impossible. See my General Chem- 

 istry, 1897, p. 378. 



Since now the atomic weight of uranium will be found to 

 be truly 240, according to unquestionable methods of work, 

 the new determinations made in this Laboratory of Armand 

 Gautier have only added another false value to the chemical 

 record. 



In fact, the work done by Mr. J. Aloy in the laboratory 



