I do not accept human or official 

 authority, but exclusively depend 

 on Nature. Page 229. 



PROLOGUE. 



The Atomic Weights of the Chemical Elements are the 

 most important of all numerical values of Nature, both 

 practically and theoretically. 



Practically, these values are used daily in all the labora- 

 tories throughout the world for the reduction of analyses, 

 and in the chemical manufactories for the estimation of the 

 proportions of materials to be used and to check the prod- 

 uct obtained. 



If the atomic weights so used are in error, even the best 

 made chemical analyses will necessarily be falsified by such 

 error. 



Theoretically, these atomic weights must be known with 

 accuracy to permit the solution of the highest philosophical 

 question of chemistry, namely, that of the UNITY OF 

 MATTER. 



Let us briefly trace the work done in this field. 



A century has passed since Dalton introduced the idea of 

 atomic weights into the science of chemistry. 



During the first half of that century, the great chemist 

 of the North, BERZELIUS, made numerous excellent deter- 

 minations of the atomic weights of all elements then known. 



Berzelius himself, and his School which comprises many 

 distinguished German Chemists, such as Rose, Mitscherlich 

 and Wohler, employed exclusively rigid methods, mainly 

 dry way operations. No fancy work of any kind was toler- 

 ated. No pretenses to extreme accuracy were made, and 

 the accuracy of the balance was never substituted for the 

 skill of the chemists. No gnats were strained at while 

 swallowing camels. 



About 1860, STAS of Brussels, started in an opposite 

 direction. The wet way silver chloride titration was made 

 a fundamental operation. Nitrates and chlorides were inter- 

 changed. Large quantities of matter were operated upon. 

 All weights were ostentatiously reduced to vacuum. 



105)031 



