244 



SCIENCE. 



answerable, * he was highly esteemed by the independent 

 members of the profession at large in Germany. The last 

 meeting of the ' German Apothecaries' Association ' which he 

 attended, reading the inaugural address, was made 

 the occasion of quiet and impressive ovations 

 which the modest man received with deep feel- 

 ing. The kind and respectful regard with which the 

 venerable scientist was treated by almost all the members 

 present, was often referred to by him in his family-circle 

 with pride and satisfaction during the twelve months which 

 were still allotted to him. He felt at that day, if ever, that 

 he had not lived in vain, and that the seed which he had 

 sown would not be lost, but that coming generations would 

 yet profit from and be benefited by it. 



Besides the works mentioned, he wrote the following: 

 The Mechanical Theory of Chemical Affinity, etc.f General 

 Theory of Motion and Force as a basis of Physics and Che- 

 mistry r Manual of volumetric Analysis r edited five times, 

 and last, but nqt least, a History of the Earth; Geology 

 founded on a new basis* which was edited twice. 



Of the various improved analytical methods devised by 

 him may be mentioned the proposal to use oxalic instead 

 of sulphuric acid (Gay-Lussac), to determine the relative 

 proportion of alkalies and acids contained in a salt; his 

 combination : Sodic Carbonate against Iodine-solution ; 

 or, better still, Sodic Hyposulphite against Iodine-solu- 

 tion, and his beautiful determination of Chlorine, by the 

 use of Argentic-Nitrate-Solution, with Potassium ( hro- 

 mate as indicator ; of the many instruments invented by 

 him, the self-acting stirring apparatus, with clock-work 

 arrangement, a pill-machine, an apparatus for prepaiing 

 infusions by the use of steam, another for extraction by means 

 of ethers, and his improved burette, with compressing 

 faucet. His Manual of Volumetric Analysis in which these 

 devices and many others of like importance are described, 

 is considered one of the first standard works in the domain 

 of analytical chemistry, and has been translated into various 

 languages. 



The attempt, first made by him in his Mechanical Theory 

 of Chemical Affinity, to promulgate the theory that chemical 

 affinity is a mode of motion, inherent in matter, and is 

 measurable onlv in so far as we can measure the heat that 

 is liberated and bound up during the union or separation 

 of two elements, is one of his greatest f fforts. Liebig| him- 

 self always valued this work very highly, and it is certainly 

 one of the most brilliant manifestations of Moiir's genius, 

 as will be seen from the following extracts: 



" The union of two bodies by combustion always liber- 

 ates a certain portion of this motion which appears in the 

 shape of heat. Another portion remains in the product of 

 combustion. We are only able to measure the former, not 

 the latter, and even of the former we are unable to say how 

 large an amount is due to one body and how much to the 

 other. If one gramme of hydrogen unites with eight of 

 oxygen, 34,462 units of heat are liberated. These indicate 

 the amount of motion which both gases contained when 

 yet ununited, as compared with the water resulting from 

 the union. In the latter itself there is yet a certain amount 

 of motion, as its liquidity and its proneness to vaporization 



1 Meohanische Theoric der chem. Affinitiit ; Braunschweig, Fr. Vieweg 

 & Solin ; 1868. 



- Allgemeinc Theorie der Bewegung und Kraft, als Grundlage der 

 I'hysik und I 'hemic ; Braunschweig, Fr. Vieweg <fc Sohn ; 1869. 



'■' Lehrbw h der chemisch-analytischen Titrirmethode ; Braunschweig, 

 I r. Vieweg & Sohn ; 1855 (1877). 



F.rde ; eine Geologie auf neuei Grundlage; Bonn, M. 

 Cohen & Sohn ; 1866 I 



Many of the suggestion; contained in his earlier work, were made 

 in tin: ' Phartn. GertM. 1 by the very me 1 who were liis lit 1 long 



ise these and other views were 1 ■ I; 1 id !tim< sharply 



1 F his oris, inal ideas on cl s than 



Pharma pecially ' 



:.■ Ill- ill 



tins line ol research which con r in 



' rermany. 



* At the eve of it! publii ation, the ;i to »Iohr as 



follows : 



i li ...k . for \ .hi s. em i" ha\ tre ited in 



iboul . in 



order to maki 10b l has n ally had a 



cleat ■ '■!" epi ion of affinii impl thai as all 1 1 has 



■.nli the melting-po : nt, thi III n, ilie boiling* 



successfully prove. From the oxygen contained in the 

 water we are able to liberate yet another amount of heat by 

 uniting it with potassium or with zinc, because potassa 

 and zinc oxide are more apyrous than either potassium or 

 zinc. Now, it is impossible to know what portion of the 

 34,462 units of heat comes from the hydrogen, and which 

 from the oxygen, and furthermore, what amount there is 

 yet in the water. Therefore, we cannot reduce to an abso- 

 lute measure this property of chemical affinity, only the por- 

 tion that is liberated in the shape of h at. 



"This example also shows how enormously more efficient 

 the motion that bodies contain as chemical afhn'tv, is than 

 that which they contain as heat. The water produced (9 

 grammes) contains 9 u. of h., while the mixture of both 

 gases before union, contained only 2}{ u. of h. (the specific 

 heat of hydro-oxygen-gas being o 25). But, since there 

 was a development of 34,462 u. of h. during their union, by 

 combustion, it follows that the motion existing in the mix- 

 ture as chemical affinity, is 15,316 times that contained in it 

 as heat." 



Again : 



" If iron develops heat while oxidizing, the dense condi- 

 tion of the oxygen in the resulting ferric oxide is certainly 

 an effect due to chemicjl affinity, but the potential energy 

 of the oxygen is no longer found in the oxide ; it has been 

 separated. The heat liberated during the combustion of 

 the iron in oxygen-gas is the surplus of motion which iron 

 and oxygen contain more than Feme Oxide." 



And again : 



" If carbon and oxygen unite to form carbonic acid, there 

 is no change of volume, and so it is with a mixture of 

 chlorine and hydrogen. Their specific gravity after chemi- 

 cal union is the same as before such union took place, be- 

 cause their volume remains unchanged ; yet a great amount 

 of heat has been liberated. 



" Thus it is not true, as has been formerly assumed, that 

 we may compare — for the purpose of measurement — chemi- 

 cal affinity to mechanical force by calculating the amount 

 of force necessary to compress a mixture of gases so as to 

 give it the density possessed by the product resulting after 

 chemical union has taken place. (Hydro-oxygen-gas 

 against water." 



The quintessence of this unique volume is contained in 

 these two theses : 



1. Loss of chemical affinity or liberation of heat always 

 means : Higher specific gravity, higher ///citing point, higher 

 boiling point, insolubility, chemical indifference, rigidity and 

 development of but little heat on combustion. 



2. Increase of chemical affinity and absorption of heat 

 always mean : Lower specific gravity, lower melting point, 

 increasing solubility, proneness to chemical combination, soft- 

 ness, development of much heat on combustion. 



Mi. CARL Mohr, in a biographical sketch of his father's 

 life and works, says of them :* 



"These two axioms comprise almost the whole range of 

 chemical processes, and they are a mechanical theory of 

 chemical affinity, in the very same sense that we have a me- 

 chanical theory of heat. 



"As an example to illustrate the first thesis, the reader 

 needs to be reminded only of the chemical relation that 

 exists between acids and liases : sulphuric acid against 

 alkalies, such as caustic potassa or quick-lime. The pro- 

 cess of saturation is accompanied by the liberation of con- 

 siderable heal ; the products have a very high melting 

 point and are chemically indifferent. 



"To illustrate the second thesis, a good example is the 

 formation of carbon sulphide. As is well known, this pro- 

 cess requires a considerable expenditure of heat, and the 



product thus obtained is volatile at a temperature far below 



the degree of temperature required for'its formation. This 

 heal, taken up by the carbon sulphide, is contained in il as 

 1 in mi. al affinity, and is evident by its low specific gravity, 

 i 1 s low boiling point, its proneness to decomposition, and 

 the increased developmenl of heat during the combustion of 

 its elements." 



The ureal principle underlying all this reasoning is that 

 of " the conservation of energy and the correlation of forces" 

 ■ ii which, as we have shown, he was the firsl exponent. f 



* . \r, kit/ der PAarmai its Vol. 216, 1880. 



t See the paper published in No. 17 of " Science," 



