TRANSACTIONS OF SICCTION L. 



659 



Skctiox B.— ClIE:\[rCAL SCIENTE. 



Pkesidest of jiie Section — 

 rrofessor Sir 11. V. Koscoe, Pli.I)., LI..I>., l-.K.S., F.(.'.S. 



TIIUIISDAY, AUGi'ST 28. 

 The Pkesident delivered the following Address: — 



Wixn the dentil of lierzelius in 184S ended a -well-miirked epncli in the history of 

 our science ; with that of Dumas — and, ala.s ! that of Wurt/ also — in 18S4 closi^s ;i 

 >ec'ond. It may not perhaps he unproiita1)le on the present occasion to frlance at 

 .some few points in tlie i^'eneral ])rofrre.s3 which cliemistry lia^^ nindo durinp: this 

 period, and tluis to contrast the position of lh(^ science in ihe'slnrni nnddraug' 

 year of ]St8, with that in the present, ])erhaps, quieter ]ierioil. 



The diderences between wliat may i)roperly l)e ternieil the Berzelian era and 

 tliat with which the luune of Dinnaswill forever be associated sliow themselves 

 in many ways, l)ut in none nim-e markedly than hy the distinct views entertained 

 us to the nature of a clieniicnl compound. 



Accordinn' to the older imtiojis, the properties of compounds are essentially 

 governed by tlie qualitative nature; of their constituent atoms, which were supposed 

 to be so arranfi'ed as to form a binary system. Under the new ideas, on the other 

 hand, it is mainly tlie numln v and arrangement of the atoms within the molecule, 

 wliich rep:ulnf(! the ciiaractei'istics of tlie componml, which is to lie looked on not 

 as built np of two conslitu'Mit u'ronps of atoms, but as i'lirmiiiir one '.'roup, 



Amony-st tluwewho successfully worlved to secure tliis impnrlant c'.iiuiire of view 

 nu a fundaimnlal question of cliemical theory, tlie name of Dumas hiniself miistr 

 first be mentioned, and, follovwupr npon liim, the preat chi'iiiicnl twin-brethren 

 liUurent and rterhanlt. wlm. u-iiiiX botli the ar<i'uinpnts of test-tube and of pen in 

 op]Kisition to the prevjiilinir \it'ws, ;xradiinlly succeeded, tiiouu'h scarcely during' the 

 lifetime of the iirst, in eoiivincin;.'' chemists tlint tln' cnnditi^ui of thing's could 

 liiirdly be ahealtliy onowlieu chemistry was truly delir.ed ' asthe seience of bodies 

 wliiidi do not exist.' ]*'or I'n'rzelius, adherinfrto his ]n'econceived notions, had been 

 forced by the press im of in'w discovery into the adoption of fnrmuhe which frra- 

 diially became more and nmre complicated, and led to more and more doubtful 

 hypotheses, nutil his folhiwers at last could barely succeed in building up the 

 original radical from its numerous supposed conqionent parts. Such a state of 

 thni;rs naturally bronglit about its own cure, and the unitiiry formula! of Gerhardt 

 bejran to be p:enerally adopted. 



It was not, however, merely as an expression of tin' nature fif llie single chemi- 

 cal compound that tliis change was benelicial, but, more jiarticularly, becanse it laid 

 open the general analogies nf similarly constituted compounds, and ])lac(Ml fact as 

 the touchstone by wdiich the constitution of these allied hodies should be ascer- 

 iiiined. Indeed, Gerhardt, in 1852, gave evidence of ilu; truth of tliis in his 

 well-known theory of ty])es, according to which, organic coin])ouiHls of ascer- 

 tained constitution can be arranged nndiH" the four types of hydroLren. hyilrochloric 

 acid, wat(n', and ammonia, and of which it is, perhajis, not loo much to say tliat 

 it has, more than any other of its lime, contributed to the dearer understanding of 

 die ndations exist Ing amongst clunnical coni])ounds. 



Another striking diiVerence of, view between the cheniistiy of the llerzelian era 

 and tliat of what we sometimes term the modern epoch is illustrated by the bo- 



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