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XXVIII. The Periodic Law, as Illustrated by certain Physical 

 Properties of Organic Compounds. — Part I. The Alkyl 

 Compounds of the Elements. By Thomas Carnelley, 

 D.Sc, Professor of Chemistry in University College, Dundee*. 



IN a previous communication (Phil. Mag. [5] xviii.p. 1) I 

 have shown how the truth of the Periodic Law* may be 

 illustrated by means of the melting- and boiling-points and 

 heats of formation of the normal halogen compounds of the 

 elements. I shall now endeavour to show how the same law- 

 is further confirmed in a similar manner by the physical pro- 

 perties of certain compounds of Organic Chemistry. For this 

 purpose we shall make use of the normal alkyl compounds 

 (methides, ethides, propides, &c.) of the elements ; and in the 

 sequel we shall find that exactly the same relations hold good 

 with these compounds as in the case of the corresponding 

 chlorides, bromides, and iodides. 



As the melting-points and heats of formation of but very 

 few of these compounds have been determined, we shall neces- 

 sarily be limited to a consideration of the boiling-points and 

 specific gravities. 



As pointed out by Mendeljeff (Ann. Chem, Pharm. Suppl. 

 1872, p. 151), elements belonging to even series (except 

 series 2) do not combine with alcohol radicals to form methides, 

 ethides, &c, whilst those belonging to odd series generally do 

 so combine. In what follows, therefore, we shall merely be 

 able to take into consideration elements belonging to odd 

 series and to the first even series only. 



Table I. contains the experimental data, with the authorities, 

 on which our conclusions are based. For the purpose of 

 avoiding minus signs, all temperatures are reckoned from the 

 absolute zero ( — 273°). The specific gravities employed w T ere 

 those corresponding as nearly as possible to 15° C. ; but it 

 was not possible to take them all at a uniform temperature 

 throughout, as in many instances there is only one determi- 

 nation on record, and that was made at different temperatures 

 in the several cases ; whilst scarcely any of them have been 

 determined at, or equally distant from, the boiling-point. The 

 following abbreviations are employed : — Me = methyl, CH 3 ; 

 Et = ethyl, C 2 H 5 ; Pr = normal propyl, C 3 H 7 ; Bu = normal 

 butyl, C 4 H 9 ; Ph = phenyl, C 6 H 5 . 



* Communicated by the Author. 



