■120 Mr. Kir wan’s Experiments 
nitre in a red-hot crucible in the ufual way ; and mixing this 
fait perfe&ly dry with flowers of fulphur in much fmaller 
quantity, as 1 believe (for I did not weigh the fait, lead: it 
ihould, during the weighing, attract moifture) I gradually 
heated the mixture in a fmall coated glafs retort, and received 
the air proceeding from it over quickfilver. 
The firft portion of air that paffed with a very gentle heat 
was that of the retort itfelf, flightly phlogifticated. It 
amounted to 1,5 cubic inches, and with Dr. Priestley’s ni- 
trous teft (that is, an equal meafure of nitrous air) its goodnefs 
was 1,29. It contained no fixed air. 
The fecond portion of air obtained by increafing the heat 
amounted to about 18 cubic inches. It was of a reddifh colour, 
and feemed a mixture of nitrous and common air. It flightly 
a&ed on the mercury. 
The third portion confifted of zo cubic inches, and appeared 
to be of the fame kind as the laft, but mixed with a little fixed 
air. 
This was fucceeded by 64 cubic inches of almoft perfectly 
pure fixed air ; and the bottom of the retort being now red, 
fiome fulphur fublimed in its neck. When all was cold, liver of 
fulphur was found in the bulb of the retort. 
Hence we fee, that the blue fmoke confifts chiefly of fixed 
air, and the white or yellow fmoke of fulphur fublimed ; and 
that no hepatic air is thus formed ; nor vitriolic air, unlefs the 
retort be fo large as to contain a fufficiency of common air to 
admit the combuftion of part of the fulphur. 
adly, That the aerial or any other acid, combined with the 
alkali, mult be expelled before the alkali will combine with 
the fulphur. Liver of fulphur exercifes a ftrong foiling power 
on the earth of crucibles, and readily pierces through them. 
The 
