I 
nitrous Acid and nitrous Air. joy 
boiling fpirit of fait to pafs through red-hot manganefe. This 
experiment did not anfwer my expectation ; the produd was a 
mixture of fixed and inflammable air. But it deferves to be 
noticed, that even in this cafe, after the effed of the fpirit of 
fait had been tried for a long time, a produdion of nitrous air 
upon the application of volatile alkali to the fame manganefe 
foon took place. 
1 6. As there are many other fubftances befides the calx of 
manganefe, which are known, per Jt\ to afford dephlogifti- 
cated air, or a mixture of this with fixed air, it was natural to 
conclude from analogy, that fiich fubftances upon the applica- 
tion of volatile alkali would not fail to afford nitrous air. 
It is beft, however, in thefe matters to truft as little as pof- 
fible to conjedures, and to bring every opinion to the teft of 
experiment. Manganefe is fo lingular a fubftance, that it is 
perhaps hardly fafe, from what happens in making trials with 
it, to infer in any inftance of another calx of a metal a fimi- 
larity of effed. Red lead, however, is known to agree in 
fuch a variety of chemical effeds with manganefe, that I find 
it difficult to perfuade myfelf that the volatile alkali properly 
applied to it would not yield nitrons acid or nitrous air* 
yet I have hitherto in vain attempted to bring this about. The 
red lead, indeed, melts during the prccefs, flows into the 
cooler parts of the tube, and often choaks the paffage of the 
air; but in fome trials a great deal of air has been collected 
before that happened, and without any fymptom of a nitrous 
mixture. It feems difficult to explain the reafon of the failure ; 
perhaps with a better adapted apparatus, and more perfeve- 
rance, either the produdion in queftion may be obtained, or 
the caufe of the failure difcovered. 
Vol. LXXIX. Yy 17. With 
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