DR. DALTON ON THE CONSTITUTION OF THE ATMOSPHERE. 
353 
delicate experiment was not enough to establish so important a law of combination, 
and I do not find that any one besides has obtained the same result*. 
Though I am not prepared to deny that sulphurets of potassium and calcium can 
be obtained by the process of Berzelius, I am quite satisfied that sulphurets of 
potash and lime, &c. may be easily procured in the dry way: of that of lime I have 
had numberless instances. As the compounds of sulphur and the alkaline earths 
have been very little subjected to investigation by chemists in general, we find great 
vacancy in the accounts given of them by the modern compilers of chemical books. 
For this reason I shall introduce here a few of the results I have obtained in a long 
series of experiments on this branch of chemical inquiry, 
Sulphuret of Lime, in the dry way. 
In 1806 I formed, for the first time, the protosulphuret of lime by heating 50 grains 
of fallen lime with 50 sulphur in a covered crucible not quite air-tight, so that the 
escape and combustion of the excess of sulphur might be allowed ; when raised to a 
red heat an addition was made to the weight of the lime ; by repeating the dose of 
the sulphur and heating, a further addition was made to the weight ; but repeating 
the operation a third time seldom made any further addition. The weight of the 
compound was 65 grains ; it was a white powder with a tinge of yellow, not caustic, 
but bitter to the taste. 
In 1809 I examined this powder more minutely, and found it was best made by 
mixing equal weights of pure hydrate of lime and flowers of sulphur, putting the 
mixture into a covered crucible and heating it slowly to red ; when the escape of the 
sulphur fumes ceases, cool the contents, and again mix them with the same weight 
of sulphur as in the first operation, and again heat it as above ; at last it will be found 
that 32 parts of hydrate of lime — 24 lime have combined with 14 of sulphur, or one 
atom to one-f'. In the work referred to I have stated that pounded lime and sulphur 
scarcely form any union by this process, and carbonate of lime and sulphur still less. 
An ingenious pupil of mine, Mr. William Barnett Watson of Bolton, has succeeded 
in uniting lime and sulphur by heat; instead of taking pounded lime, which has a 
harsh gritty feel, he takes hydrate of lime, and expels the water by a red heat con- 
tinued till 32 parts of hydrate are reduced to 24 ; this is a fine soft powder ; when 
24 parts of this pure and finely divided lime freed from water are well mixed with 
24 parts of sulphur and heated red in a covered crucible, a partial combination takes 
place, and an increase of weight to the lime ; this operation is to be repeated till the 
additional weight becomes 14 grains, after which no further addition can be effected. 
Mr. Watson found it require several repetitions. I have since found it may be effected 
by two or three only. This sulphuret is not used in eudiometry. 
* Annals of Philosophy, 1822. 
f See New System of Chemical Philosophy, vol. ii. pages 99 and 102. 
