4 PREFACE. 



ing them. On the other hand, I have rigidly excluded 

 atomic weights calculated from analyses never designed so 

 to be used. Any chemist, upon whose experiments we 

 could rely, would proceed in a very difterent manner in 

 making an atomic weight determination, from that which 

 he would select for an ordinary analysis, and to put his 

 credit at stake by calculating atomic weights from analyses 

 not designed for this use is alike unfair to him and to the 

 scientific public, which is asked to receive as an atomic 

 weight determination what really is not such. 



The purpose of this paper is distinctly not critical, and 

 the remarks I have added to, or inserted in, the digest are 

 simply explanatory. I have, however, frequently mentioned 

 criticisms -which have appeared in literature when they 

 seemed pertinent. 



As for the accuracy with which the digests have been 

 made, I may state that the preponderating importance of 

 this point has been constantly before my mind. In the 

 effort to crowd the maximum amount of information into 

 the fewest words, I have had occasion to refer to most of 

 the papers digested a number of times, and at long inter- 

 vals. I have always taken advantage of such occasions, as 

 well as those on which I have met with a reprint, transla- 

 tion or abstract of a determination, to verify the rough 

 draughts of my digests. Only in a couple of instances have 

 I thus discovered a trifling error. On the other hand, I 

 have been able to detect and point out numerous misprints 

 and miscalculations in the original sources. While, there- 

 fore, I cannot hope entirely to have escaped error in tHe 

 thousands of values I have copied, and the almost equal 

 number of calculations I have made, I have strong hopes 

 that the accuracy of this digest will be found at least on a 

 par with that of the original papers. 



When, as is the case with provoking frequency, chemists 

 have given their analytical data, but have omitted to state 

 the atomic weights, or other constants, assumed in calculat- 

 ing their results, I have recalculated their data with accepted 

 constants, which I hav-^e in each case stated. I have also, iu 

 many instances, recalculated determinations of importance, 



