484 i-HiLOSormcAL transactions. [anno 1784. 



uniformly through the liquor; whereas if it had been owing to fixed air, it would 

 have taken up some short time before it appeared, and would have begun first at 

 the surface, as was the case in the above-mentioned experiment with nitrous air. 

 What it was really owing to I cannot pretend to say ; but if it did proceed from 

 fixed air, it would show that only an excessively minute quantity was produced.* 

 On the whole, though it is not improbable that fixed air may be generated in 

 some chemical processes, yet it seems certain that it is not the general effect of 

 phlogisticating air, and that the diminution of common air is by no means owing 

 to the generation or separation of fixed air from it. 



As there seemed great reason to think, from Dr. Priestley's experiments, that 

 the nitrous and vitriolic acids were convertible into dephlogisticated air, I tried 

 whether the dephlogisticated part of common air might not, by phlogistication, 

 be changed into nitrous or vitriolic acid. For this purpose, I impregnated some 

 milk of lime with the fumes of burning sulphur, by putting a little of it into a 

 large glass receiver, and burning sulphur in it, taking care to keep the mouth of 

 the receiver stopped till the fumes were all absorbed ; after which the air of the 

 receiver was changed, and more sulphur burnt in it as before, and the process re- 

 peated till 122 grs. of sulphur were consumed. The milk of lime was then 

 filtered and evaporated, but it yielded no nitrous salt, nor any other substance 

 except selenite ; so that no sensible quantity of the air was changed into nitrous 

 acid. Now, as the vitriolic acid, produced by the burning sulphur, is changed 

 by its union with the lime into selenite, which is very little soluble in water, a 

 very small quantity of nitrous salt, or any other substance which is soluble in 

 water, would have been perceived. 



I also tried whether any nitrous acid was produced by phlogisticated common 

 air with liver of sulphur ; for this purpose I made a solution of flowers of sulphur 

 by boiling it with lime, and put a little of it into a large receiver, and shook it 

 frequently, changing now and then the air, till the yellow colour of the solution 

 was quite gone; a sign that all the sulphur was, by the loss of its phlogiston, 

 turned into vitriolic acid, and united to the lime, or precipitated ; the liquor was 

 then filtered and evaporated, but it yielded not the least nitrous salt. The ex- 

 periment was repeated in nearly the same manner with dephlogisticated air pro- 

 cured from red precipitate ; but not the least nitrous acid was obtained. 



It is well known that common selenite is very little soluble in water ; whereas 

 that procured in the 2 last experiments was very soluble, and even crystal- 

 lized readily, and was intensely bitter; this however appeared to be owing 

 merely to the acid with which it was formed being very much phlogisticated ; 

 for on evaporating it to dryness, and exposing it to the air for a few days, 



* Dr. Priestley also found no fixed air to be produced by the explosion of inflammable and com- 

 mon air, vol. 5, p. 124. — Orig. 



