Chlorides. 







NC)3(?) 







— 



PCI3 • 







PCI, 



VCl, 



YCl, 





As Cis 



— 



— 









Nb 0\, 



SbC!3 



— . 



SbCls 





— 



Ta CJ, 



266 Mr. M. M. Pattison Miiir on Chemical Classification, 



— va 



— .13i CI2 Bi CI3 — — 



Eacli of these elements forms an oxide Xg O5 ; but ihesQ oxides 

 are possessed of different degrees of stability, of fusibility, &c. 

 K2 O5 is possessed of no great stability; it melts at a low tem- 

 perature. P2 O5 sublimes unchanged at a red heat, but is 

 entirely deoxidized by heating with carbon. V2 O5 is also 

 easily reduced by heating in hydrogen, or in contact with 

 carbon ; it melts at a high temperature \vithout decomposition. 

 As2 O5 is reduced to As2 O3 by heat alone. Sbg O5 is also 

 reduced by heating ; and Bi2 O5 loses oxygen at 150°. On the 

 other hand, Nb2 O5 and Tas, O5 neither melt nor volatilize, nor 

 are they decomposed at a white heat. ISTiobic oxide becomes 

 crystalline at a very high temperature ; this oxide is also 

 reduced by heating in hydrogen, while tantalic oxide is only 

 reduced by contact with charcoal at a very high temperature. 

 ISTow these two elements, which form the most stable and the 

 least-easily reducible pentoxides, also form pentachlorides 

 (NbClo and Ta CI5) which are capable of existing in the state 

 of gases. VCI4 appears to be capable of existing for a time in 

 the gaseous state. P CI5 and Sb CI5 are split up into P CI3 

 and CI2, and Sb CI3 and CI2, respectively, when heated. BiClg 

 does not exist. 



Now, if we examine the positions of these eight elements 

 upon the curve of atomic volumes and atomic weights, we find 

 certain points of interest. Nitrogen is situated near a 

 minimum-point ; it is preceded and followed by electro-nega- 

 tive elements (carbon, oxygen, and fluorine); the differences 

 between the atomic volumes of nitrogen and its immediate 

 neighbours (assuming Meyer's numbers for the specific gravity 

 of solid nitrogen, oxygen, and fluorine to be approximately 

 correct) are not great ; there is no well-marked electro-posi- 

 tive element in the neighbourhood of nitrogen. Phosphorus 

 has a somewhat similar position in the third section of the 

 curve ; it is placed, however, further from the minimum- 

 point than nitrogen ; and right over against it, as it were, is 

 the well-marked positive element magnesium : this element 

 occupies the position on the descending portion of the curve 



