November 3, 1904J 



NATURE 



It should be stated, however, that some attempt is 

 made to introduce quantitative notions into llie 

 qualitative methods by using roughly weighed 

 amounts of the substances ; but the effect is somewhat 

 discounted by the frequent omission of the quantity 

 and strength of the reagents. I refer more particu- 

 larly to the use of " drops," which may vary con- 

 siderably in bulk, and to the omission of the strength 

 of the acids. 



Prof. Liversidge attaches great importance to 

 the study of qualitative analysis as a means as well 

 as an end of chemical education. It is an opinion 

 very widely held, and is well worth discussing. 



The fact is sometimes lost sight of that chemistry 

 is a handicraft as well as a science, and that its 

 science is as yet not exact. 



Perhaps there is no branch of chemistry wherein 

 the skill of the craftsman is in greater demand, or 

 the inexactness of the science more clearly emphasised, 

 than in ch-emical analysis. 



.\ student may study intelligently the reactions for 

 individual elements, and so learn their properties; but 

 he finds that when they are mixed they behave 

 differently, and the more observant and careful he is 

 the more will these subtle influences, which conform 

 to no equation, become apparent. 



No substance is insoluble ; mass action is a power- 

 ful factor; a precipitate will carry down a substance 

 which should, for all he knows, remain in solution, 

 and a substance will retain another in solution 

 which, for equally occult reasons, should form a 

 precipitate. 



Tables for the analysis of mixtures, which are 

 based on the behaviour of single substances by a 

 process of simple logic, become artificial and illusory, 

 and give a sense of false security which subsequent 

 experience alone can dispel. 



Is this a subject for extended study on the part of 

 a beginner in chemistry? In the opinion of the 

 writer the preparation of simple substances and a 

 careful study of their properties, into which the 

 general principles of qualitative and quantitative 

 analysis are introduced, is his proper sphere of work. 

 The host of reactions and elaborate tables of separa- 

 tions, and still more the countless precautions, 

 Kunstgriffe, and manipulative details of practical 

 analysis are a part of the handicraft of the specialist 

 in chemistry. To thrust this work upon a beginner 

 who is not to be a specialist is almost equivalent to 

 expecting a student of mechanics, who is not to be 

 an engineer, to work a lathe or use a planing 

 machine. 



The crux of the whole question lies in this, that 

 qualitative analysis is a branch of practical work, call- 

 ing itself chemistry, which can be easily adapted to the 

 process of examination. Were the practical examin- 

 ation banished from the syllabus and replaced by note- 

 books supervised, signed and submitted by the 

 responsible demonstrator or teacher of recognised 

 standing, the mass of ill-digested analytical tests and 

 tables would soon vanish from the curricula of 

 schools and colleges, and its place supplied by a series 

 of rational exercises. J. B. C. 



NO. 1827, VOL. 71] 



BOOK SHELF. 



By F^lix Le Dantec. Pp. 

 -Mean, 1904.) Price 



OUR 



Les Lois natiirelte 



xvi + 3oS. (Paris: Felix 



6 francs. 



Just as " anyone can play the piano " with a piano- 

 player, so anyone can write a book on the philosophy 

 of science. The result gives satisfaction and pleasure 

 to the performer in one case and to the writer in the 

 other, but whether his particular interpretation is 

 equally satisfymg to an outsider is another question. 

 The effects are, however, more lasting in the case 

 of the author, for we are getting such an enormous 

 accumulation of books on space, matter, force, the 

 ether, and laws of nature that it is becoming a 

 wonder who finds time to read them or even to cut 

 their pages, if the publisher has failed to attend to his 

 proper duties in this respect. 



Let us examine how M. Le Dantec deals with 

 thermodynamical considerations. In commencing 

 he supposes bodies to have definite thermic masses, 

 and he defines quantities of heat by the products of 

 these masses into the changes of temperature. He 

 also enunciates the principle of conservation of heat 

 according to which the heat gained by one body is 

 equal to that lost by another. But in the first place 

 the quantities which he calls thermic masses are not 

 constant for the same body between the same limits 

 of temperature, but they also depend on whether the 

 changes take place at constant pressure or constant 

 volume; and, in the second place, his equation of con- 

 servation of heat is contrary to common experience 

 of what happens when two rough bodies rub against 

 each other. In the ne.xt chapter the author goes on 

 a different tack, and speaks of the equivalence of 

 quantities of work and quantities of heat, quite 

 regardless (to all outside appearances) of the fact 

 that the term " quantity of heat " is meaningless 

 except in the case of passage of heat from one body 

 to another. In the next chapter the author condemns 

 the use of the term " quantity of heat " altogether. 

 What ideas can a reader form of the nature of 

 physical laws after perusing such a series of chapters 

 as this? 



Nature Teaching. By F. Watts and W. G. Freeman. 

 Pp. xi+193. (London: Murray, 1904.) Price 



This little book forms a welcome change from the 

 many appearing under similar titles in that it is 

 avowedly based upon experiments, and treats of 

 things about which the writers really know and have 

 not merely read up. Dealing in the main with the life 

 of the plant, it describes a simple series of experiments 

 within the capacity of an elementary school or an even- 

 ing continuation class, illustrating the function of seed, 

 root, stem, leaf. Sec, and amplifying the knowledge 

 thus obtained with further examples drawn from the 

 practice of the garden or the farm. A certain lack of 

 definiteness in the description of experiments militates 

 at times against the spirit in which the book has been 

 conceived; in a subject where everything depends upon 

 the cultivation of accurate observation and rigorous 

 scientific method the authors should not allow them- 

 selves to fall into the slipshod generalised accounts of 

 things which are the bane of so much of the current 

 teaching of this nature. For instance, in their account 

 of striking cuttings, the authors do not direct attention 

 to the differences in the management of herbaceous 

 and woody cuttings, the time of year at which they 

 should be struck, and so forth, so that the teacher with- 

 out experience would be apt to fumble over the matter 

 at first, and would in real life be discouraged from try- 

 ing any experiments in this particular direction unless. 



