NATURE 



209 



THURSDAY, JANUARY 



1SS4 



THERMAL CHEMISTRY 

 Thermochemische Untersuchungcn. Von Julius Thomsen, 

 Dr. Phil, et Med., &c. Volumes I., II., and III. 

 (Leipzig : Johann Ambrosius Bartli, 1882-83.) 



A PAPER was published in this journal a short time 

 ago calling attention to " The Backward State of 

 Chemistry in England" (vol. xxviii. p. 613) ; the writer 

 regrets that so little attention is paid to the chemistry of 

 the carbon compounds, and that so much time is spent in 

 our chemical schools in elementary and routine instruc- 

 tion. In the second of these regrets I can thoroughly 

 sympathise ; our so-called students of chemistry are be- 

 coming mere machines which perform, and generally 

 perform badly, mechanical processes knowa as qualitative 

 and quantitative analyses. We hear complaints from 

 physical laboratories that practical physics is taught in 

 an unsystematic manner; we sometimes have comparisons 

 drawn between the desultory methods of teaching pursued 

 in these laboratories and the orderly and systematic 

 courses of practical chemistry conducted in the work- 

 rooms of the sister science. But I am afraid it is rather 

 the chemist who is to be pitied : his method is too 

 methodical; it seems to succeed because it neglects the 

 really scientific aspects of chemistry. Chemistry is a 

 great branch of science ; but what is the so-called prac- 

 tical chemistry of the schools or the examination .'' It is 

 but a wear)' round of dull repetition ; it consists of obtain- 

 ing black precipitates, and yellow precipitates, and colour- 

 less precipitates, precipitates which are soluble and those 

 which are insoluble ; it occupies itself with filtering and 

 washing, and drying, and burning, and weighing ; it has 

 little or no connection with the problems which belong to 

 the science of chemistr)-. But when the author of the 

 article to which reference has been made attributes the 

 backward state of chemistry in England to the compara- 

 tively small amount of attention which is given to organic 

 chemistry, I find myself unable to agree with him. I 

 think we are apt to be dazzled by such things as the 

 synthesis of indigo, or the artificial manufacture of 

 alizarin : we forget to inquire whether the study of 

 organic chemistr)- has in recent years added any great 

 general principle to chemical science. The conception 

 of the valency of elementary atoms is certainly an out- 

 come of the study of the carbon compounds, or rather of 

 the application of the atomic theory to this study ; but 

 have we not of late made too much of this conception ? 

 has it not rather stopped than aided inquiry? is it not 

 time we had given up our "bonds," our "units of 

 affinity," which are chiefly remarkable as being change- 

 able almost at pleasure ? Organic chemistry, as pursued 

 in the German laboratories, it seems to me, has almost if 

 not quite entered on the same path as that which his led 

 qualitative and quantitative analysis to so sad a fall : it is 

 in danger of ceasing to be a branch of science and of 

 becoming an art of manufacture. Any student who goes 

 through the course of preparation of organic compounds, 

 systematised so well in the laboratories of the German 

 universities and elsewhere, is ready to manufacture new 

 Vol. XXIX.— No. 740 



co'Tipout.ds by the score; the difficulty consists in not 

 making such compounds. There are whispers abroad 

 that he who is not in the trade is regarded by the German 

 professors as "no chemist." 



I think the evil lies deeper : we are so anxious to act 

 that we have no time to think. The chemist may gain a 

 kind of reputation by making new compounds ; the 

 process requires no thought, no scientific training, no 

 originality. It has also something to be said in its favour. 

 Nature is so vast that we can scarcely hope to gam any 

 accurate knowledge save by attacking the problems in 

 detail. In chemistry, as in other branches of science, we 

 must be content to gain "a series of small victories" over 

 nature. But in fighting nature in detail we are apt to 

 lose sight of general principles by the help of which alone 

 can empiricism become science. I think that in che- 

 mistry, and more especially perhaps in organic chemistr)', 

 we are specialising too much : we are trying to solve large 

 and complex problems by a series of small attacks all 

 delivered from the same point. What then is the remedy ? 

 I would answer : Vary the points of attack ; remember 

 that the victory is to be gained only by boldness, and that 

 it is emphatically worth gaining. Do not let chemistry 

 remain the battlefield of the Philistines, but enliven it 

 with the true spirit of science, with that spirit which will 

 not believe that the universe is a " rubbish-heap of con- 

 fused particulars," but will rather regard it as a vast 

 organism in which while " everything is distinct yet [is] 

 nothing defined into absolute independent singleness." 



That the points from which the problems of chemistry 

 may be attacked are many is witnessed by the book 

 before us. Why is there no handbook of thermal che- 

 mistry in English ? Will not some one at least translate 

 Naumann's "Handbuch"? M. Thomsen has for years 

 been known as one of the two great workers in the field 

 of thermal chemistry ; his contributions to this branch of 

 science have been numerous and important ; we cannot 

 be too thankful that he has gathered these contributions 

 together, and arranged and digested them in this series 

 of volumes, which must remain as the groundwork of the 

 science. Three volumes have appeared, and a fourth (to 

 treat of organic compounds) is promised. Let me try to 

 give soine account of one or two points in Thomsen's 

 work. 



The notation of thermal chemistry is simple : Let r = 

 the thermal value (stated in gram-units) of a chemical 

 change ; if the change consist in the formation of a 

 definite quantity of a compound X^ Y^ Z^ — made up of 

 a parts of X, b parts of Y, and c parts of Z — then 



r = [X% Y", Z=] -f ; 1 

 if the same compound is produced in presence of a large 

 quantity of water, then 



r = [X^ Y^ ZS Aq] + ; 

 if the same substance already formed is dissolved in an 

 unlimited quantity of water, then 



r = [X-' Y" Z'^, Aq] -f. 

 The general expressions for the production and decom- 

 position of a compound X_, Y,, are 



(i)X, + Y,= X,Y„ + (X%Y^'); 

 and 



(2)X,Y, = X, + Yl,-(X^Y''). 



■ Th iinsen always wri'es the in Jlces above tiie elenienMry symbols when 

 these symbols occur in thermal equations 



