NOMENCLATURE AND NOTATION, CHEMICAL. 



617 



toward the discovery of those general princi- 

 ples which, it has been assumed, must hold 

 true in respect to the chemical nature and re- 

 lationships of different substances, and to the 

 chemical phenomena they can exhibit; and, in 

 fine, at once toward a comprehensive and or- 

 derly grouping of bodies, elementary and com- 

 pound, and a unitary and philosophical system 

 of the truths ascertained concerning them. 



Such being the important ends to be kept in 

 view, it has naturally happened, among the 

 multitude of experimenters and theorists en- 

 gaged in the work, that, in the first place, many 

 of the suggestions and hypotheses put forward 

 have sooner or later been proved untenable and 

 valueless ; and that, in the second place, a con- 

 siderable degree of conflict and collision has 

 unavoidably existed, both in respect to the 

 views presented and to claims as to priority in 

 advancing them. This ordeal of new views in 

 chemistry has been similar to that through 

 which, some two and three centuries earlier, the 

 mechanical and certain of the physical sciences 

 were passing. Indeed, in the realm of chemical 

 science, the clash of opposing views has not yet 

 ceased ; and while there are chemists who still 

 withstand, as unsupported or unnecessary, the 

 recent theories respecting combinations and 

 eqirivalencies, and the new system of names it 

 has been proposed to introduce, it is also true 

 that some at least of the principles referred to, 

 as well as in some instances the claims to their 

 origination, are still in question, and must await 

 the decision of the future. Still, so large a pro- 

 portion of the leading chemists of the world 

 have taken part in developing the new views, 

 or have already given assent to them, that we 

 can no longer doubt their ultimate practical ac- 

 ceptance (subject to such extensions or modifi- 

 cation as further research shall introduce), as 

 the basis and doctrines of the science, in the 

 new form in which it is to pass from the pres- 

 ent to future times. Eecognizing both the 

 changes already accomplished, and the neces- 

 sity for continued labors in the same direction, 

 Professor Miller, in his opening address before 

 the chemical section of the British Association, 

 1865, and in connection with a reference to 

 certain researches in organic chemistry, said : 



"In these and kindred investigations, the 

 necessity for the introduction of fixed principles 

 of nomenclature for regulating the construction 

 of names for the recently discovered compounds 

 has been sensibly felt ; and indeed the changes 

 in notation rendered necessary by the altera- 

 tion in the values assigned to the atomic weights 

 of many of the chemical elements have rendered 

 a general revision of the system of chemical 

 nomenclature a matter of pressing importance." 



It is not surprising that, in the application 

 of the new views of chemical combination, 

 some outstanding and apparently irreconcilable 

 facts are yet to be met with. But, admitting 

 this, it is still safe to say that the period under 

 consideration has effected the growth of a 

 chemical philosophy which is largely new; 



that it has established new conceptions of the 

 molecular constitution of bodies, both element- 

 ary and compound ; that it has thus necessitated 

 new ideas of chemical equivalency and reac- 

 tions, and a new scheme of symbolic notation ; 

 while, recently, it has witnessed the attempt to 

 replace the imperfect system of names for com- 

 pound bodies hitherto in use, by one that, at 

 least both flexible and improvable, may yet be 

 developed into a precision and completeness 

 adequate to the constantly growing require- 

 ments of the case. 



Basis of the Old and of the New Notation. 

 From the time of the promulgation by Dalton, 

 during the first few years of the century, of his 

 discoveries respecting the combination of bodies 

 in definite and fixed equivalents by weight, 

 down quite or nearly to the present, the gen- 

 eral theory of chemical changes or reactions, 

 as held by a large body of chemists and adopted 

 in text-books on the subject, and of course also 

 the notation employed to represent the products 

 of such reactions, have been essentially such as 

 grew out of or harmonized with those views of 

 the distinguished philosopher named. Strange 

 to say, however, within a very few years of the 

 publication of Dalton's views (as early, indeed, 

 as 1808), Gay-Lussac made known another class 

 of facts respecting at least those bodies existing 

 or obtainable in the aeriform state ; and facts 

 which, after the lapse of a full half-century, are 

 now at length only just admitted to their due 

 place and force in connection with the theory 

 of chemical reactions and of the constitution of 

 elementary and compound bodies. Illustrations 

 of the application of Dalton's primary law, but 

 without reference to the combining volumes in 

 the case, are seen in the determination, by the 

 most recent and accurate experiments, of the 

 equivalents or combining weights of the ele- 

 ments hydrogen, chlorine, oxygen, nitrogen, and 

 carbon, as respectively 1, 35.5, 8, 14, and 6 ; 

 the ultimate atoms of these bodies being sup- 

 posed also to have weights corresponding to 

 the numbers so ascertained. Now, Gay-Lussac 

 found that temperature and pressure remain- 

 ing the same elements in the aeriform state 

 also combine invariably in certain simple rela- 

 tions by volume, the volumes of the products 

 furthermore bearing some simple ratio to the 

 sum of volumes of the components. Thus, 2 

 vols. H. combine with 1 vol. 0., resulting in 2 

 vols. water-vapor; 2 vols. N. with 1 vol. O. 

 form 2 vols. nitrous oxide; 1 vol. N. with 1 

 vol. 0. forms 2 vols. nitric oxide; 3 vols. H. 

 with 1 vol. N. form 2 vols. ammonia ; 1 vol. H. 

 with 1 vol. Cl. forms 2 vols. chlorhydric acid 

 gas, etc. 



This principle of combination by volumes, 

 until recently admitted into the text-books of 

 the science rather in the manner of an inci- 

 dental circumstance, has at length, as already 

 implied,, come to be seen as of coordinate im- 

 portance, in the determining of cornbining- 

 ratios and the constitution of compound bodies, 

 with the more familiar principle of equivalents 



