( 272 ) 
way. In the first case o-dinitrodiphenylsulphide NO,C,H,SC,H,NOg, 
in the second o-dinitrodiphenyldisulphide NO,C,HsSSC;HyNOg, is 
formed, sodium nitrite being simultaneously produced. 
The monosulphide is readily oxidised, first to a sulphoside and 
then to a sulphone; the molecule of the disulphide on the other 
hand is broken up and converted into two molecules of o-nitroben- 
zenesulphonic acid, of which some derivatives were prepared. By 
means of sodium disulphide it is therefore possible to substitute the 
sulphonic group for a nitrogroup in the orthoposition. From p-di- 
nitrobenzene, neither the dinitrodiphenylsulphide nor the corresponding 
disulphide could be obtained; in this respect, therefore, it differs 
from its isomer. Both with Na,S and with NaS, reduction to 
p-dinitroazoxybenzene first occurs; this substance has already been 
obtained by the action of potash on p-dinitrobenzene.°) Small quantities 
of p-nitrothiophenol NO.C,HySH are also formed. Parachlornitroben- 
zene, the behaviour of which with Na,S has already been studied 
by Nisrzki and Boruor, reacts also with Na.S, forming paradini- 
trodiphenyldisulphide NO CsH,SSC,;H,NO,. The crystals of this 
compound, which has already been prepared by LeEucKART®) by 
another method, have the interesting peculiarity of flying to pieces 
when warmed to 134°, subsequently melting at 170°. Inversely, 
the solid mass formed below 170° changes at the same temperature 
into another crystalline modification in a clearly visible manner. 
We are here obviously dealing with a transition point characterised 
by a great difference in the specific volumes of the two modifications ; 
this is to be more carefully investigated. 
Like the isomeric ortho-compound, p- dinitrodiphenyldisulphide is 
readily oxidised to nitrobenzene sulphonic acid. By this means, 
therefore, halogen united to the benzene nucleus has been replaced 
by the sulphonic group. 
The results of some preliminary experiments make it probable 
that by direct substitution substances containing not only two, 
but also more sulphur atoms, connecting two benzene rings, may 
be prepared. 
The investigation is being continued. 
*) Recueil 18, 122. 
°) J. Prakt. Chem. (2) 41, 199; see also WinuGEropt, Ber. 18, 331; KEHRMANN 
and Baurr, Ber. 29, 2361. 
