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Proceedings of the Boyal Society 
nitrous acid, the nitrites and the nitroso-suhstitntion products ; 
pentatomic in the ammonia salts, in nitric acid, and the nitro-substi- 
tution products. P triatom ic in PH3, PCI3, phosphorous acid, and 
the phosphites ; pentatomic in PCI5, POCI3, H3PO4, HPO3, &c. ; 
C diatomic in CO, and tetratomic in almost all other compounds ; 
a large number of such examples might be adduced, but these may 
suffice. 
No chemist, however, as far as I know, except Kolbe and 
V. Oefele has assumed a similar variety in the atomicity of sulphur. 
I had long suspected that such a variable atomicity must he attri- 
buted to sulphur, but the remarkable discoveries of v. Oefele have 
to my mind placed it beyond a doubt. Indeed, so strong does the 
evidence appear to me, that I should not have thought it necessary 
to trouble the Society with this note, had I not observed that 
some of our most eminent theoretical chemists, as Hofmann and 
Foster, still represent S as diatomic in such compounds as SOg and 
H2 SO4. I have therefore gathered together what seem the most 
cogent arguments in favour of the variable atomicity of sulphur. 
That S is diatomic in H^S and the corresponding metallic sul- 
phides, in the mercaptans and alkyl-sulphides, is quite obvious, and 
is admitted by all. I need therefore spend no time on this part 
of the subject. Let us then turn to those compounds in which 
there is reason to suspect the presence of tetratomic sulphur. 
These are SO2, SO CI2, M2SO3, S(C2H5)3l, and its derivatives. The 
latter series of substances discovered by v. Oefele seem to me quite 
inexplicable, except by the assumption of tetratomic sulphur, and 
I have never seen an attempt to explain their constitution in any 
other way.* But even leaving them out of the question, the most 
natural explanation of the constitution of SO2 and M2SO3 is, that 
their sulphur atom is tetratomic. Formula can, indeed, be con- 
structed with diatomic sulphur, which represent the composition o«f 
these bodies; but if we examine these formulas we easily see that 
^ Wurtz, in a note to a paper by v. Oefele on “ Diethyl Sulphan in the 
Bulletin de la Societe Chimique de Paris for February 1865 , formulates that 
among other sulphur compounds on the assumption of diatomic sulphur. But 
it must be remembered that this body (02115)2802, contains in the molecule 
only two monad radicals, so that it takes its place beside chloride of sulphury! 
rather than in the series, since discovered by v. Oefele, of which the starting- 
point is the iodide of triethyl sulphin 8(02115)31. 
