OF THE 



UNIVERSITY 



PART FIRST. 



The Errors of Precision in Atomic 

 Weight Determinations. 



I. GENERAL INTRODUCTION. 



By the new term of Absolute Atomic ./eight we desig- 

 nate the exact number expressing the atomic weight of any 

 element, that of carbon-diamond being taken at f-velve 

 exactly. 



We are well aware that it is commonly considered im- 

 possible to determine this exact atomic weight. But we 

 believe this opinion of chemists of the present due to their 

 habit of considering the determinations of atomic weights 

 a purely laboratory operation only. 



The determination of the atomic weight of any element 

 involves, however, two entirely distinct problems, the one 

 chemical, the other mathematical. 



The Chemical Problem. 



The chemical problem consists in the production of the 

 material, its chemical change into some other definite form, 

 and the accurate determination of the ratio of the weight of 

 these two materials. 



Such a process we have in the reduction of pure lead oxide 

 to metallic lead when moderately heated in a current of dry 

 hydrogen. 



This is one of the fundamental processes devised by 

 Berzelius. 



In the chemical symbols, also devised by him, the above 

 oxide is represented by Pb O. 



