216 M. Pcttenkofer on the Atomic Weights of the Elements. 



The existence of series tends to show the close connexion be- 

 tween inorganic and organic chemistry ; and the various series 

 whose existence has been pointed out have this in common with 

 the series of organic chemistry, that the fii-st member conditions 

 the chemical character of the succeeding members. The che- 

 mical character of methyle is seen in the successive radicals ; and 

 the chemical character of fluorine exhibits itself in chlorine, bro- 

 mine and iodine ; that of oxygen in sulphur, selenium and tel- 

 lurium ; and that of nitrogen in phosphorus, antimony and 

 arsenic. 



With the consideration of this subject, and with the determi- 

 nation of other equivalents, Dumas is still engaged; and these 

 speculations mil appear more important when he publishes the 

 study of a natural family which is derived from hydrogen as the 

 first member, and in which the physical properties of the che- 

 mical elements stand in close connexion with the place which 

 each assumes in the series. 



Pettenkofer* has republished a paper, read by him eight 

 years ago before the Bavarian Academy of Sciences, in which 

 he discusses the relations between the equivalent weights of the 

 elements. The conclusions which he endeavoured to establish 

 were, that the equivalents of the inorganic elements which fonn 

 natural families or groups exhibit among themselves just as con- 

 stant differences as do the equivalents of compound radicals which 

 belong to one natural group. And simple inorganic elements 

 may therefore be considered from the point of view of the com- 

 pound organic radicals. 



For the full development of his views it was necessary to have 

 a complete revision of the elements, which at that time Petten- 

 kofer was unable to undertake. 



Marignac has made a i-edetermination of the atomic weights 

 of barium, strontium, and lead. To previous determinations of 

 the atomic weight of barium, in which anhydrous chloride c^f 

 barium was used, the objection had been raised that it was im- 

 possible to dehydrate crystallized chloride of barium without at 

 the same time driving off some chlorine ; and in fact it was found 

 that chloride of barium, kept for some time at a red heat, does 

 become slightly alkaline. Without going into the question 

 whether chloride of barium, which has not been raised to a tem- 

 perature sufficient for a slight decomposition, does not still 

 retain some traces of water, Marignac obviated it by employing 

 in his determination crystallized chloride of barium, which could 

 be obtained perfectly pure, of a definite composition, and which 



* Licbifr's Annnlen, February 1858. 



