220 ATOMIC WEIGHT ANALYSES. 



A few elements have found no record at all ; no serious 

 work of permanent value could be found. 



The non-valent elements have been omitted, for the 

 present time. Theoretically they are most important; see 

 General Chemistry, 1897, pp. 380-381, and Principles, 1874, 

 pp. 180-181. 



These non-valent elements will be fully considered in a 

 contemplated special work on the unity of matter. 



In several places we have made use of a contracted form 

 of tabular representation, as already done, page 100. 



We found it sufficient to give, first, our absolute atomic 

 ratio ; second, the chemical formula of the substance and 

 product actually used; third, the extremes and range, and 

 fourth, the analytical excess of the mean, 



It will readily be seen that these four particulars really 

 are fully sufficient and imply all the details essential. 



To a few elements we have devoted more space than may 

 seem proper; for example, to arsenic. But on careful read- 

 ing, it will be found that nothing could have been omitted 

 without real loss to the subject. 



This record furnishes an excellent indication of analyt- 

 ical work urgently needed. 



But in order to be available, the fields thus indicated 

 must be worked thoroughly and conscientiously. 



We must cease to run hobbies, to follow routine; we 

 must again be severe in the choice of methods, as in the first 

 half of the nineteenth century. 



The methods of the school of Berzelius must be revived, 

 and checked by our methods of calculation and criticism. 



At the same time the severity of our requirements are 

 revealed in our finding it impossible to assign a definite 

 atomic weight for several elements for which numerous 

 determinations have been made, all more or less con- 

 flicting. 



Thus, for palladium the value 106 has generally been 

 accepted, and 106.5 seems to result from Reiser's determi- 

 nations. But these results are probably all too high. 



