nitrous Acid and nitrous Air . joy 
{lightly red, and this rednefs will increafe on admitting atmo- 
fpherical air. 
The cauftic alkali fhould be ftrong, and as far as I have ob- 
ferved the longer the procefs is continued, the ftronger will 
be the nitrous air produced. At lead this evidently appeared 
to be the cafe in feveral inftances, where the operation was 
continued for a long time. 
In moft inftances, on the very commencement of this pro- 
cefs, afmall jar ot the air thus collected difcovers by the Jmell 
a nitrous impregnation. But it fometimes happens, that feve- 
ral j ars of air may be collected, and the admiffion of atmc- 
Ipherical air to them will not produce a fenfibly red colour. 
Here, however, there exifts a caufe of deception againft 
which the operator ought to be on his guard, left he fhould 
conclude that no nitrous air is formed, when in reality there is 
a confiderable quantity. The volatile alkali, notwithftanding 
every precaution, will frequently pafs over in great quantities 
undecompofed. If the receivers are filled with water, a great 
part of this will indeed be prefently abforbed; but ftill fome 
portions of it will mix with the nitrous air formed by the pro- 
cefs. Upon admitting the atmofpherical air, the nitrous air is 
decompofed, and the red nitrous fumes inftantly combine with 
the volatile alkali. The receivers are prefently filled with 
white clouds of nitrous ammoniac ; and in this manner a 
wrong conclufion may eafily be drawn, from the want of the 
orange colour of the nitrous fumes. A confiderable quantity 
of nitrous air may have been formed, and yet no orange 
colour appear, owing to this circumftance ; and therefore it is 
eafy to underftand how a fmall quantity of nitrous air may be 
moft effe&ually difguifed by the fame caufe. 
3 
12. Thefe 
