68 
PROFESSOR R. THRELFALL AND MR. J. H. D. BREARLEY 
obtained in a pure state, there is no more difficult substance to remove from the sulphur* 
(compare Monckman, loc. cit.). It is altogether a most unsatisfactory body to deal 
with. 
The Gaseous Contents of Sulphur. —On heating sulphur in vacuo , there is no doubt 
that gases are given off, even from the purest samples. The following is an account 
of some experiments made on this subject in connection Avith Avhat will later on be 
described as the “ Film of November 18th, 1892.” It may be premised that this was 
a film which had been rapidly cooled from a high temperature, after having been part 
of some sulphur which had caught fire in an atmosphere containing much carbonic 
acid gas, and which looked rather dirty. The sulphur composing this film was found 
to give off a good deal of gas on heating; so, on November 22nd, 1892, a quantity of 
recovered sulphur, twice distilled, Avas selected for an experiment having for its object 
the determination of the conditions under which gas is given off and absorbed by 
sulphur. The sulphur Avas melted under an air-pressure of about 5 centims. of 
mercury ; the results were—r- 
Hardly any gas was given off till the thermometer rose to 3 78° C., and then 
the evolution of gas increased up to 190° C. At this point the increased \fiscosity of 
the sulphur prevented the bubbles coming off, but they were still being formed. At 
about 230° C. the bubbles began to separate from the sulphur, and continued to do 
so up to the boiling-point. There Avas nothing like a sudden evolution of gas at any 
temperature. The next day the sulphur was re-heated to 240° C. under similar 
conditions, but not a single bubble of gas could be detected. 
A question now arose as to the nature of the gas. Is it air ? If so, shaking up 
the sulphur with air Avhile it cools from the boiling-point might be considered to be 
likely to induce more air to get absorbed. This was tried, but no bubbles were given 
off on re-heating under an air-pressure of 5 centims. of mercury only. Is the gas 
carbon dioxide ? The last experiment Avas repeated in an atmosphere of carbon 
dioxide, but again no gas Avas driven off’ on re-heating. Has the gas anything to do 
Avith the sulphur being on fire ?— i.e., is the gas an oxide of sulphur dissolved from an 
atmosphere mainly composed of this oxide ? To test this, the sulphur Avas heated to 
boiling-point and set on fire in a platinum dish, a bell jar Avas placed over it, and the 
sulphur was agitated freely. It Avas then re-transferred to the vacuum-bath and 
tested as before, but little or no gas came off. 
These experiments give no clue as to what the gas given off really is, but a Auiluable 
result is that, Avhen once the gas has been caused to come off, remelting will not 
cause more gas to be absorbed. In view of the more important questions awaiting 
solution, Ave judged it unadvisable to spend any time in further determining the 
nature of the gas, as we possibly might have done in a vacuum-tube by the help of 
spectroscopy. We conclude, hoAvever, that the purest distilled sulphur ought to be 
* 1893.—It can be done however by continued extraction with carbon bisulphide—at all eA r ents fairly 
well (see end of pajjcr). 
