584 DR MACVICAR ON THE LAW OF VOLUMES OF AERIFORMS 



Undecompo sable Bodies. 

 Oxygen, 16; Sulphur, 32; Selen. 80; Tellur. 128.'' 



Of these the three last, as is Avell known, are most closely allied, and to all 

 appearance isomorphous. But they diifer remarkably in weight. Hence, of the 

 three, S, the lightest, alone can attain completely to the icosatom. The heaviest, 

 Te, can attain only to the octatom. While that which is intermediate, Se, give both. 



Sulphur . G = ^ = %^. =1-975. Expt. 1-98. 



Tellurium . G = f^^ = _ -^ =632. Expt. 6 • 3. 

 ^Se,o_ 80x20 _^.g^ \ 



2AQ 648 



Selenium . G = ^ 



Se„ 80 x8 _-^ -c, ,.o -.o 



|Ai = T62-='-^*- j^-Pt- 4-3 . . . 4-8. 



SesSe^o =4-44. 1 



SegSe^oSe, =4-21. ) 



Oxygen does not belong to the same category as these three substances. 

 Oxygen is, in reference to sulphur, what fluorine is in reference to selenium. 



Ozone, which is a name for oxygen in every state except that in which it 

 exists in the atmosphere (and probably for more), shows by the disappearance of 

 volume when it is generated, that oxygen is capable of the molecular or dense 

 state, though it cannot be thrown into this state by mechanical pressure. From 

 carbonic acid we may infer what the molecular form and specific gravity of 

 similarly condensed oxygen would be ; for all the habits of fixed air, compared 

 with those of oxygen, and all the relations between oxides and carbonates in 

 nature, lead us to infer that carbonic acid is not only isovoluminous with atmo- 

 spherical oxygen, and, like the latter, contains a couple of atoms of oxygen in one 

 normal or atmospherical unit, but differs from it only by carrying an atom of 

 carbon as a nucleus between the two atoms of oxygen (whence, of course, its 

 physiological relations must be completely changed). Now, with regard to 

 carbonic acid which has been condensed, the dodecatom gives — 



Carbonic Acid . G^^^^^= ^\l}^ = -815. Expt. at zero, -803. 

 AQ 324 ^ ' 



* I have here taken the atomic weights of this group of bodies as it stands in the unitary nota- 

 tion. But I must hei-e add, that our molecular theory gives these numbers, not as atomic, but as 

 molecular weights, proper to the smallest regular polyhedron, viz., the tetrahedron, so that the S, Se 

 and Te of the unitary system are in ours, S^, Se^ and Te^, while the O of the unitary system, which is 

 truly an unit of oxygen gas, is in ours a coupled molecule = (Q), or Og. Sulphur as S^ exists free, 

 and unites with hydrogen and metals ; and, in a word, functions as 0. As S, on the other hand 

 (being the alternate or reciprocal form of 0), it unites with O, and when by itself forms an icosatom 

 820, which is of course also the nucleus of (8^)25 ; but S^q differs from (SJ,g, at least when secularly 

 consolidated, in possessing metallic lustre, and in being very stable, if not undecomposable. Its 

 existence as a separate substance has only been obscurely detected. But for the sake of reference, 

 it may be called Sulphurium ; its symbol 820= 8 x 20 = 160. 



