220 



NA rURE 



[January 5. 1905 



standard American procedure. We think this is wise, 

 and, while we endorse his opinion that only the best 

 work should be aimed at, we do not think that this 

 means that the very elaborate American analyses 

 should be emulated by the ordinary worker. From 

 twenty to twenty-five elements are usually sought for 

 by the .American chemists, and nearly one-half of these 

 may be present in less than i per cent, of the total 

 rock. Such analyses look exceedingly well on paper, 

 but require the greatest experience and manipulative 

 dexterity if they are to be trustworthy. Moreover, 

 their value is as yet not beyond question. Certainly 

 an analysis in which ten or twelve elements are deter- 

 mined as exactly as possible is more welcome than an 

 analysis which is more elaborate but less accurate. 

 We notice that the author discourages the routine 

 execution of duplicates. No doubt this is right ; they 

 take up much time, and may be useless or misleading ; 

 it is better for the experienced chemist to occupy 

 himself in the most thorough testing of his re- 

 agents, the purity of which is never above suspicion. 

 Still, there can be no doubt that duplicate analyses 

 do show how far it is possible for the results to vary 

 when two samples of the same powder are analysed. 

 They help to check any exaggerated confidence in 

 analytical refinements. In this respect it would be 

 interesting to know what are the probable limits of 

 error in analyses executed by the methods given in this 

 book. The author gives his opinion (apparently not 

 founded on any special investigations), and it strikes 

 us that he is more sanguine in this respect than the 

 majority of experienced silicate anal}'sts in Britain or 

 on the Continent. 



OUR BOOK SHELF. 

 Application of some General Reactions to Investi- 

 gations in Organic Chemistry. By Dr. Lassar- 

 Cohn. Translated by J. B. Tingle, B.A. Pp. loi. 

 (New York: Wiley and Sons; London: Chapman 

 and Hall, Ltd., 1904.) Price 4s. 6d. net. 

 It would be difficult to say with what object and for 

 what class of readers this little volume (it is scarcely 

 more than a pamphlet, and may be read in an hour) 

 was written. Yet anyone engaged in the practical pur- 

 ■suit of organic chemistry cannot fail to be interested 

 in it. One may say roughly that the book treats of 

 the unsystematic part of organic chemistry, i.e. of the 

 ■ordinary reactions which do not succeed, and how they 

 may be made to do so. 



Without always offering a very satisfactory explan- 

 ation of the causes of success or failure, for the terms 

 " protective influence " and " contact action " are 

 after all merely names, the author points out how an 

 apparently unimportant modification may affect the 

 whole course of a reaction and convert an unprofitable 

 method into a successful or commercially lucrative 

 ■one. Incidentally, he urges the systematic study of 

 these anomalous reactions. 



As an example may be mentioned the well known 

 fact that the accidental introduction of a few drops of 

 mercury into the experimental vessel, in which the 

 preparation of phthalic acid from naphthalene was in 

 progress, rendered the operation and consequently the 

 production of artificial indigo a success. 



As a rule the difficulties encountered by the 

 anomalous behaviour of organic compounds are met 

 not by more drastic treatment, but by milder reagents. 



NO. 1836, VOL. 71] 



The whole trend of modern organic synthesis seems 

 to lie in this direction. Thus the caustic alkalis have 

 been replaced in many cases by alcoholic solutions of 

 sodium ethoxide, by diethylamine, pyridine, or chalk, 

 the strong mineral acids by phosphoric, boric, or one 

 of the organic acids. High temperatures have given 

 place to lower ones. The days of so-called " pyro- 

 genic synthesis " are past. No one nowadays makes 

 organic compounds by the aid of a red-hot tube. 



In this connection it is suggestive that the funda- 

 mental reactions of living matter which embrace 

 oxidation and reduction of a far-reaching kind, as well 

 as synthetic processes more complex than anything 

 achieved in the laboratory, are all effected at ordinary 

 temperatures and with the mildest reagents. 



It follows, therefore, that the more closely organic 

 chemists succeed in imitating these conditions the 

 more surely will those mysterious contact or ferment- 

 ation problems usually associated with living proto- 

 plasm, but not unknown in the laboratory, approach 

 solution. J. B. C. 



.4 Further Course of Practical Science. Bv J. H. 



Leonard and \A . H. Salmon. Pp. ix + 224. 



(London : John Murray, 1904.) Price 2S. 

 Ix this book the principles of natural science are 

 taught and enforced in a scientific manner by means 

 of a course of experimental work, simple in character, 

 but involving quantitative measurements, and carried 

 out personally by the student. To begin with, lengths 

 are measured with an ordinary rule, and tests are 

 made in order to find out the limits of accuracy within 

 which the measurements may be relied on. These 

 measurements serve as an introduction to " physical 

 arithmetic," or simple arithmetical computations 

 specially suitable for dealing with numbers which are 

 avowedly only approximately correct. Then follows a 

 chapter on elementary mensuration involving the 

 estimation of angles, lengths, areas, and volumes, the 

 balance very wisely sharing in this work. 



Experiments are devised to illustrate some of 

 the fundamental properties of matter, such as those 

 of indestructibility, inertia, porosity, ductility, &c. 

 The next six chapters deal with mechanics, the sub- 

 jects including uniform linear acceleration, Newton's 

 laws, relative motion, statical equilibrium of uniplanar 

 forces, and simple machines. This difficult section is 

 not treated in a very satisfactory manner. The 

 method is too deductive, the experiments are some- 

 what scanty and not very well chosen. Thus there 

 is no direct verification of the fundamental principle 

 of the conservation of momentum. Vectors, though 

 introduced, are not made sufficiently prominent, and 

 in the so-called " simple machines " it seems rather 

 antiquated to find the three kinds of levers, the three 

 systems of pulleys, the wedge, &c., introduced. 



In the concluding chapters relating to the properties 

 of liquids and gases, and the nature of heat, the 

 authors are happier in their treatment, notwithstand- 

 ing an occasional looseness in the statement of a 

 principle. The book deserves to be very favourably 

 received, and teachers will find that arrangements 

 have been made to facilitate the purchase of the 

 apparatus necessary for conducting the experiments. 



Die drahtlose Telegraphie. By Dr. Gustav Eichhorn. 



Pp. x + 256; numerous figures. (Leipzig: Veit and 



Co.) Price 5 marks. 

 This is an elementary exposition of the principles and 

 practice of wireless telegraphy with especial reference 

 to the svstems developed by Dr. Braun. It is evidently 

 intended to enable a practical man to become 

 acquainted with this method without, at the same 

 time, any attempt being made to give such a complete 



