INTRODUCTION. 



About tAvo years ago, while engaged upon the study of some 

 interesting points in theoretical chemistry, the compiler of the fol- 

 lowing tables had occasion to make frequent reference to the then 

 existing lists of specific gravities. None of these, however, were 

 complete enough for his purposes. Bottger's work was too old, and 

 not suitably arranged ; and the tables published in the various larger 

 treatises on chemistry were lamentably small. Accordingly he pre- 

 pared a set of Specific Gravity Tables for his own private use, withou^- 

 view toward publication. The material proved abundant; revisions 

 and re-revisions became necessary, and, finally, it seemed to the writer 

 advisable to complete and publish the tables. And in the final revi- 

 sion the boiling and melting points, and the references to original 

 papers were - added. 



Of course, having grown out of the individual needs of the com- 

 piler, the character of the tables has been shaped by the nature of the 

 work upon which he was at first engaged. It was necessary for him 

 to compare the specific gravities of similar compounds of the same 

 elements, and to arrange them in series. In consequence it will be 

 found, on reference to those portions of the tables containing organic 

 compounds, that no rigid theoretical arrangement could well be fol- 

 lowed. It would be very well, doubtless, to be able to compare at a 

 glance the properties of ethyl and all its compounds, or of benzol 

 and all its derivatives. But such an arrangement would necessitate 

 the comparison of hydro-carbons with oxygenated, chlorinated, nitro- 

 genous, or organo-metallic bodies ; or, in other words, the comparison 



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