CHEMICAL SCIENCE. 



1 ON THE NEW SYSTEM OF CHEMICAL PHILOSOPHY. 



The following is an abstract of an address made by Prof. Odling, on 

 assuming the chair of the Chemical Section of the British Association, at 

 its last meeting, 1884. "After the great diversity, or rather antag- 

 onism, of opinion which has existed for the last dozen years or so* I am 

 almost bound to take a somewhat prominent notice of one substantial 

 agreement which now prevails among English chemists as to the com- 

 bining proportions of the elementary bodies, and the molecular weights 

 of their most important compounds. The present unanimity of opinion 

 on the fundamental subject, among those who have given it their atten- 

 tion is, I conceive, greater then has ever been the case since Dalton 

 published his new system of Chemical Philosophy, more than half a 

 century ago. As yet, indeed, the unanimity of practice falls considerably 

 short of the unanimity of belief; but even in this direction great progress 

 is being made. As was well observed by Dr. Miller, at a previous meeting 

 of this Association, 'Chemistry is not merely a science; it is also an art, 

 which has introduced its nomenclature and its notation into our manu- 

 factories, and in some measure even into our daily life; hence the great 

 difficulty of effecting a speedy change in chemical usage alike so time- 

 honored and intimately ramified.' I propose, with your permission, to 

 make a f w remarks upon the history of this chemical reformation, more 

 especially in connection with certain points which some of its most dis- 

 tinguished leaders have scarcely, I think, correctly estimated. From the 

 time when Dalton first introduced the expression 'atomic weight,' up to 

 the year 1842, when Gerhardt announced his views upon the molecular 

 constitution of water, there does not seem to have been any marked dif- 

 ference of opinion among chemists as to the combining proportions of the 

 principal elements. That 1 part by weight of hydrogen, united with 

 36 parts by \veight of chlorine to form a single molecule of hydrochloric 

 acid, and with 8 parts by weight of oxygen to form a single molecule of 

 water, was the notion both of Berzelius and Gmelin, who may be taken 

 as representatives of the two chief continental schools of theoretic che- 

 mistry. There was, indeed, no difference of opinion whatever between 

 them as to the combining proportions of the three elements. Using the 

 hydrogen scale of numbers, both chemists represented the combining pro- 

 portion of hydrogen as 1, that of chlorine as 36, and that of oxygen as 

 8. Both, moreover, represented the molecular weight of hydrochloric 

 acid as 37, and the molecular weight of water as 9 True it is that 

 Berzelius professedly regarded the single combining proportions of hy- 

 drogen and chlorine as consisting each of two physical atoms; but since 

 the two atoms of hydrogen, for instance, which constitute the one com- 



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