434 



NATURE 



[March 9, 1899 



relation between melting points and the composition of 

 chemical compounds. It occupies twenty-seven pages, 

 and was begun in 1897. For an account of the periodic 

 character of the melting points of the elements, reference 

 is made to the second volume of the book, the fusing 

 points of compounds only being dealt with in this chapter. 

 A few examples of the fusing points of inorganic com- 

 pounds are given, showing that those of the chlorides, 

 bromides and iodides of the elements of a period fall with 

 the increase of atomic weight ; the period chosen being the 

 second in the periodic table beginning with sodium, and 

 ending with chlorine. When the haloid compounds of a 

 group are examined, it is found that, generally speaking, 

 the fusing points rise with an increase of atomic weight ; 

 this is exemplified by the compounds of the beryllium 

 and nitrogen groups, but the haloids of the alkali metals 

 behave irregularly. Tables iv. and v. give the melting 

 points of isomeric organic compounds, in which it is 

 seen that the symmetrical compounds melt at higher 

 temperatures than the unsymmetrical. In the next 

 table the fusing points of the para- meta- and ortho- 

 compounds of benzene are compared, and it is shown 

 that the para-compounds always fuse at the highest 

 temperatures, whilst in the case of the sulphamides the 

 ortho-compounds have the highest fusing points. More 

 complex compounds are then studied, and the chapter 

 contains no less than thirty-nine tables, in which the melt- 

 ing points of allied chemical compounds are compared. 



The fifth chapter is also by Dr. Willy Marckwald, on 

 the relation between the boiling points and the com- 

 position of chemical compounds. This was begun in 

 1897, and extends over twenty-nine pages. The chapter 

 deals with organic compounds only, and contains forty- 

 one tables giving the boiling points of bodies of various 

 series. In some of the tables boiling points under vary- 

 ingpressures both above and below that of the atmosphere 

 are included. 



Chapter vi., on the relation between refraction and the 

 chemical composition of bodies, was written in 1897 by 

 Dr. E. Rimbach, and consists of ninety-seven pages, the 

 first twenty-three of which are devoted to generalities in 

 which the different methods of determining refractive 

 indices are briefly mentioned and the three formula for 

 calculating the specific refractive powers of bodies pro- 

 posed by Laplace, by Dale and Gladstone, and by Lorenz 

 and Lorentz are discussed, comparison being made of 

 the constancy of the numbers obtained by the use of the 

 different formuhc under varying conditions. The follow- 

 ing section is on molecular refraction and the constitu- 

 tion of bodies ; isomeric liquids are first considered, and 

 it is shown that the differences of refractions of such 

 bodies are not great unless there is a pronounced dif- 

 ference in their chemical structure ; thus those bodies in 

 which double bonds are supposed to exist, have different 

 refractive powers from those in which single bonds 

 occur ; and it is seen that in homologous series the 

 difference of CH., makes a nearly constant difference in 

 the molecular refraction of the suljstance, and by sub- 

 traction the value of CHj is obtained. Similarly the 

 values of carbon, hydrogen and oxygen are calculated, 

 the latter element showing different numbers according 

 to the other elements with which it is combined in the 

 molecule. The atomic refraction of the constituents of 

 NO. 1532, VOL. 59] 



a compound when added together should give the mole- 

 cular refraction of the compound, but in cases in which 

 the carbon atoms are doubly or trebly linked a difference 

 is always found, and from these differences the values of 

 multiple bonds are obtained. Cyclic compounds are next 

 considered, and the effect of the three double bonds in 

 the benzene ring is shown by the comparison between 

 the observed and calculated molecular refractions of a 

 number of benzene derivatives. The atomic refraction 

 of the halogens is then studied, followed by some ob- 

 servations on molecular dispersion. The next section 

 is on compounds containing nitrogen, and here it is seen 

 that the atomic refraction of nitrogen varies according to 

 the way in which it is combined in the various substances. 

 The atomic refraction of other elements such as sulphur, 

 phosphorus, arsenic, antimony, silicon, mercury, tin and 

 lead are next dealt with. There is a short section on the 

 refractive powers of gaseous bodies, and another on those 

 of solids and of their solutions. The concluding section 

 treats of electrical molecular refraction and the relation 

 between dielectric constants and the constitution of 

 bodies. 



The next chapter, on the relations between the chemical 

 nature and the spectra of elementary and compound 

 bodies, was written in 1889 by Prof, (ierhard Kriiss, and 

 after his death in 1895, his brother, Dr. Hugo Kriiss, 

 wrote some additions. The chapter consists of twenty- 

 five pages, and the addenda of seven. Emission spectra 

 are first considered, and the relations between the wave- 

 lengths of the lines in the spectra of various elements are 

 shown to be the same as those between the overtones of 

 a fundamental note, tables being given comparing the 

 observed and calculated wave-lengths of the spectral 

 lines of certain elements ; the characteristics of the 

 spectra of the elements of various groups are described, 

 and also the relation between the spectra of compounds 

 and those of their constituents. Absorption spectra of 

 inorganic compounds are briefly mentioned, whilst those 

 of organic compounds are fully treated and the alterations 

 of the spectra by the introduction of different radicals are 

 noticed. In the additions made by Dr. H. Kriiss the 

 remarkable investigations of Kayser and Runge on the 

 several series of lines in the emission spectrum of an 

 element are dealt with, and the connection between these 

 observations .md the periodic law are shown. There is 

 also a short discussion on the variation of absorption 

 spectra of solutions in connection with the ionic hypo- 

 thesis. We do not find any notice of .Xbney's researches 

 on the absorption in the infra-red part of the spectrum 

 by organic bodies. 



The eighth chapter, of eighty-four pages, deals with 

 the relation between the optical rotation of organic 

 substances and their chemical composition, and was 

 written by the editor. Dr. H. Landolt, and finished in 

 1898. For methods of measuring circular polarisation 

 reference is made to Part I. The rotation of the plane 

 of polarisation by crystals is briefly mentioned, and a list 

 is given showing the rotation for plates 1 m.m. in thick- 

 ness and also the systems to w-hich the crystals belong. 

 The rotation by liquids follows, a list of thirty groups of 

 active substances being given, and the method of finding 

 the specific molecular rotation is described. The specific 

 rotation of dissolved substances and the changes which 



