April 28, 1899.] 



SCIENCE. 



607 



enter upon entirelj' new fields of research. 

 The pupils of the great masters of organic 

 chemistry ,Liebig, Dumas, Hofmann, Wurtz, 

 Kolbe, Kekule and others, found enough to 

 do in following in the footsteps of their 

 teachers, and were little inclined to seek 

 new pastures. The requirements of candi- 

 dates for the doctorate, whereby tlie experi- 

 mental material for the dissertation had to 

 be accumulated in a comparatively short 

 time, led to the assignment of topics with 

 which the instructor was familiar, and 

 which were fairly sure of giving positive re- 

 sults within a year or two, and, as we all 

 know, no branch of chemistry yields results 

 so readily as the study of carbon compounds, 

 with its highly developed synthetical meth- 

 ods. As the Chemiker-Zeitung has recently 

 pointed out, even at the present day the 

 full professorships in German universities 

 are almost invariably held by organic chem- 

 ists, while inorganic chemistry ie left to 

 subordinates. The weight of authority and 

 influence being on the side of organic chem- 

 istry, the student who looks forward to a 

 university career sees that his chances of 

 promotion are better if he follow the organic 

 rather than the inorganic direction. I need 

 hardly add that the more mercenary hope 

 of obtaining a new dye-stufif or a now rem- 

 edy, or of replacing nature in making an 

 alkaloid, has also been a powerful incentive 

 to many. 



Let us now consider some of the reasons 

 which have their root in the chemical pecul- 

 iarities of carbon, and which render its 

 compounds, at least those which are not 

 too complex, comparatively easy to study. 

 These conditions are not peculiar to carbon, 

 but no other element, as far as is known' 

 presents as many of them at the same time' 



1. Carbon compounds being very gener- 

 ally soluble in neutral solvents, frequently 

 crystalline, and often volatile without de- 

 composition at comparatively low tempera- 

 tures, are peculiarly adapted to separation 



in a state of purity by fractional crystalli- 

 zation or distillation, and for the same rea- 

 son it is usually possible to determine their 

 true molecular weights. The very general 

 possession of melting or boiling points lying 

 within easily observable ranges of tempera- 

 ture greatly facilitates identification. 



2. The power of carbon of uniting, atom 

 to atom, to form chains, the form and size 

 of which can be easily regulated by known 

 synthetic methods, and the stability of 

 which is sufficient to allow of manipulation 

 under easily attainable conditions, is a 

 marked peculiarity of this element. This, 

 with the power of forming stable compounds 

 with hydrogen, is the basis of the defini- 

 tion of organic chemistry as ' the chemistry 

 of the hydrocarbons and their derivatives.' 

 "With regard to self-linking power the 

 other elements are in marked contrast. 

 "VVe know with certainty no compounds in 

 which two atoms of boron are linked, not 

 more than four nitrogen atoms have been 

 arranged tandem, while of silicon, the near- 

 est relative of carbon, we know at best a 

 half-dozen well-defined compounds with 

 two atoms of this element in series, and 

 but one with three ; analogues of the hydro- 

 carbons are unknown, with the exception 

 of silico-methane, and the instability of 

 this is sufficient proof that a series of silicon 

 paraffines would be most dilficult to pre- 

 pare, aud the same would apply to all 

 classes of silicon compounds in which self- 

 linking is a prerequisite. It does not ap- 

 pear probable that we shall ever have a 

 very extensive chemistry of the ' hydrosil- 

 icons aud their derivatives.' Among the 

 compounds of other elements self-linkage 

 occurs in but few cases and is limited in 

 extent. 



3. It is a highly important property of 

 carbon compounds that their molecules tend 

 to preserve their individuality ; they gener- 

 ally do not, though there are exceptions, 

 gpontaneously avail themselves of opportuni- 



