[40 



NA TURE 



[December 12, 1895 



law), we deduce a differential equation for the work obtained or 

 required in isothermal changes. The change under consideration 

 may involve external work, as when a vapour or gas is generated 

 against atmospheric pressure ; or it may be internal work of 

 different kinds, as when the molecules are endowed with 

 increased kinetic energy in volatilising, or when a compound is 

 decomposed into its constituents, with increased potential energy. 



A somewhat difficult but important paper by J. Willard 

 Gibbsi treats of the equilibrium of heterogeneous substances, 

 giving deductions from the two laws of thermo-dynamics, which 

 in turn become major premises for a host of further deductions ; 

 so broad, indeed, are the propositions of Gibbs, that the distinc- 

 tions between chemistry and physics do not appear ; there may 

 be two " heterogeneous substances" of like chemical nature, as 

 water and its vapour ; there may be three chemical bodies, as 

 limestone with the lime and the carbon dioxide obtained by 

 ignition ; or there may be several physical mixtures, as solution 

 of water in ether, solution of ether in water, and the mixed 

 vapour resting upon both liquids. Now, a little consideration will 

 .show the importance of knowing when equilibrium is established, 

 for this is equivalent to saying that no further action can take 

 place ; the solution is saturated, no longer acting upon the salt ; 

 or the gas which has been generated under pressure is no longer 

 evolved. When a change takes place spontaneously, as when I 

 drop a stone, or mix sulphuric acid with water, heat is developed 

 Irom some other form of energy. To reverse the process, work 

 must be done. The conversion of heat into work is limited by 

 natural law ; when a given change implies the doing of work, and 

 that work is forbidden by the terms of our major premise, the 

 change is impossible, equilibrium prevails. 



"Osmotic pressure" in dilute solutions is analogous to the 

 pressure of gases ; the Gay-Lussac-Marriotte law, with slight 

 modification of terms, applies to molecules in the liquid state. 

 If work is required to diminish the volume of a gas by means of 

 pressure, work is likewise required to diminish the volume of a 

 body in dilute solution, whether the solvent be removed by 

 evaporation or by freezing. Boiling point and freezing point of 

 the solvent are changed by the presence of the dissolved body. 

 The agreement of observed facts with theoretical deductions 

 has led to important methods of determining molecular weights, 

 while the apparent discrepancies in the case of electrolytes have 

 proved an important argument for the doctrine that these 

 compounds are dissociated into their ions. 



The mutual indebtedness of technology and pure science has 

 already been pointed out. Manufacturing processes afford 

 many examples of change which are not carried to completion ; 

 it is important to know how far the operation can be improved 

 to afford a larger yield, a purer product or less waste. Com- 

 bustible gases issue from the blast furnaces. There is still a 

 great reducing power in this mixture of carbon monoxide with 

 carbon dioxide. Can it be utilised by enlarging the furnace ? 

 Immense furnaces were built in order to secure a larger yield of 

 iron, but the results were disappointing. The law of mass action 

 shows that the equation 



Fe.Ps + 3CO = 2Fe 4- 3CO. 

 is limited by certain conditions of equilibrium, and that the ratio 

 of the two oxides of carbon could not be greatly improved over 

 that already secured in practice. The expense of a technological 

 experiment might have been saved, had the indications of 

 mathematical chemistry been heeded. 



What hopeless confusion seems to prevail in our present 

 knowledge of solubilities ; yet how important in the separations 

 required for chemical analysis. Here, again, we deal with 

 questions of equilibrium. Will work be done at the expense of 

 heat or not ? 



There are two special difficulties in the general application of 

 thermo-dynamical principles : first, the minor premise is often 

 wanting; and, second, the mathematical form of reasoning is 

 often difficult for the best laboratory workers. Among the 

 published data of thermo-chemistry, some have been determined 

 directly, some indirectly ; it is often difficult to find the data 

 desired, or to judge of their accuracy. A critical compilation of 

 all available thermal data, conveniently arranged for reference, 

 with at least some indication of fhe probable errors, would be 

 very desirable. Many such data might be computed indirectly 

 from experimental determinations of equilibrium. Many 

 empirical equations have been computed, showing solubility as 

 a function of temperature. Who will trace the correlation 



1 Trans. Conn. Acad , 3, 108, 343 (1874-78). See also, Amer. Jour. Sci. 

 [3I16, 441(1877); 18, 277 (1878). 



NO. 1363, VOL. 53] 



among such, and thus add a large chapter to thermo-chemistry ? 

 What genius shall discover that form of mathematical function 

 that shall iubstitute rational for empirical equations with a clear 

 interpretation for each constant required? "But this work is 

 mathematical rather than chemical," you will say. Yes, it is- 

 applied mathematics ; and mathematicans (not being chemists) 

 are not likely to undertake such a task for us, unless we ask 

 their counsel and aid. Specialisation is inevitable ; yet by too 

 arbitrary a specialisation, we may inadvertently lose the very 

 help we need. Again would I emphasise the fruitfulness which fol- 

 lows a "cross-fertilisation of the sciences" (Journ. Amer. Cheni. 

 Soc, 15, 601 (1893). Judging from the advances recorded in. 

 late years, especially in the Zeitschrift fiir physikalische Chetnie, 

 it is safe to predict great developments for the rising generation. 

 I heartily echo the sentiment that we need more data ; yet great 

 stores of observations upon record have not yet been coordinated 

 and put to use. Ostwald, desiring to know the influence of free 

 iodine upon a reduction process, made three series of determin- 

 ations (twenty-four in all) from which he concludes that the 

 influence is 7tot proportional to the mass. It was no part of his 

 purpose to discover what the law of retardation is ; but others 

 might well follow out this clue, using also the data supplied by 

 Meyerhofifer, and supplementing these with further experiments 

 if needed. A glance at the literature of solubilities, and the 

 lack of rational formula to express broad generalisations, may 

 convince us that a great mine, with abundant ore " in sight," is 

 awaiting development ; or, rather, that ore has been run through 

 a stamp-mill to extract half the gold, while fully half still 

 remains in the tailings, awaiting more perfect methods of 

 treatment. 



Much may be learned from the systematic habits of the 

 astronomer, dividing his work among the several observatories in 

 a spirit of helpful co-operation, and assigning the labour of 

 computation to those who are fitted thus to follow the lead of 

 others. What better service can we do for the University 

 student than to set before him some of the problems in mathe- 

 matical or physical chemistry that require patient toil, and give 

 him the pleasure of assisting in their .solution by the use of 

 logarithms and squares ? What is more practical than to utilise 

 any service he can render ? 



In conclusion, I beg leave to suggest the appointment of a 

 joint Committee (representing Sections A, B and C of the 

 American Association) to consider the feasibility of striving 

 towards the following ends : 



(i) The compilation of all reliable data of physical chemistry 

 in convenient form for reference, distinguishing those determined 

 directly from those calculated indirectly. 



(2) The calculation of empirical formulae, to combine any 

 series of data, when some better form of generalisation is not 

 already at hand. 



(3) The preparation and use of rational formulae, wherever 

 possible, to deduce the natural constants from series of observa- 

 tions, and to express the conditions that may be expected to 

 hold between observations of different kinds. 



(4) The organisation of a band of volunteer compilers and 

 computers from among advanced students, who (with the 

 counsel and aid of their instructors) may assist in the work of 

 compiling data and computing formulae. 



While the time did not seem ripe for the appointment of such 

 Committee at the late meeting of the A. A. A. S., the writer 

 would be pleased to receive any further suggestions from those 

 interested, regarding the points noted above. 



RoBT. B. Warder. 



UNIVERSITY AND EDUCATIONAL 

 ■ INTELLIGENCE. 



Oxford.— At the i6oth meeting of the Junior Scientific Club, 

 held on Wednesday, November 17, the following officers for 

 next Term were elected :— President, E. C. Atktnson ; pernia- 

 nent treasurer, D. H. Nagel ; treasurer, N. V. Sidgwick ;. 

 biological secretary, R. Warren ; chemical secretary, H. P. 

 Stevens ; editor, A. W. Brown ; committee, R. A. Baddicom, 

 M. Hesketh, T. J. Garstang. It was announced that Prof 

 W. Ramsay had consented to deliver the fifth Robert Boyle 

 Lecture in the Summer Term, 1896. 



Cambridge.— The late Mr. James Carter has bequeathed his 

 collection of fossil Crustacea, on which he was a recognised 

 authority, to the Woodwardian Museum. A portrait of the late 



