96 
to sulphurie acid, hence 9°/, of the sulphur present in the 2 gram- 
mes of P,. In a duplicate experiment 13.5 °/, of the sulphur was 
oxidized. In this product the sulphur was, therefore, oxidized only 
for a small part or at least very slowly by bromine water at the 
ordinary temperature. When on the other hand a mixture of 
charcoal with 2 °/, sulphur was treated in the same way with bromine, 
the sulphur present was quantitatively found back as sulphuric acid, 
as was to be expected. 
Bebaviour towards hydrogen. 
In a preliminary experiment 0.90 gramme of P, were spread out 
in a thin layer in a porcelain boat, and slowly heated in a current 
of pure dry hydrogen. Up to 500° no formation of sulphuretted 
hydrogen could be found; this began at about 550°. In two hours 
the temperature was raised from 550 to 750°; in this temperature 
range sulphuretted hydrogen was slowly but regularly developed. 
About '/, of the sulphur originally present in the P, was converted 
to sulphuretted hydrogen. 
In a second experiment 2 grammes of P, were heated in a hydrogen 
current; at 430° sulphuretted hydrogen began to evolve. When 650° 
was reached, this temperature was kept constant, till the regular 
generation of sulphuretted hydrogen diminished. The heating at 650° 
had then been continued for 5 hours. The temperature was then 
raised to 750°, which gave rise to the formation of some more 
sulphuretted hydrogen. After the heating at 750° had been continued 
for four hours, only very little sulphuretted hydrogen was slowly 
developed, after which the experiment was stopped. The quantity of 
sulphuretted hydrogen formed corresponded to 0.0281 gr. sulphur 
or 70°/, of the quantity present in 2 grammes of P,. 1.945 grammes 
of carbon were recovered, which contained 0.47 °/, sulphur. Hence 
23°/, of the sulphur present in P, has remained behind in the 
carbon that is left. 
In a third experiment 2 grammes of P, were heated for some 
days in a hydrogen current. The temperature was between 500 — 
700° for 9 hours, and between 700 —800° for 11 hours. Throughout 
_ the experiment sulphuretted hydrogen was regularly generated. The 
remaining carbon still contained 0.29°/, sulphur; it is, therefore, 
possible to convert practically all the sulphur from P, to sulphuretted 
hydrogen by prolonged heating in hydrogen at 500—800°. 
To verify whether really a particular action of hydrogen should 
be assumed here, 1 gramme of P, was heated in a current of pure 
dry nitrogen at 900—990° for 8 hours; this appeared to have reduced 
the sulphur content only little. The percentage of sulphur found 
