[ae J 
Of all the metallic fubftances, 
mercury feems to be the beft to 
obtain nitrous air of a conftant qua- 
lity ;. but heat muft be applied, if a 
large quantity is required in a fhort 
time. 1 made ufe, a long while 
ago, of pin-duft, of which a {mall 
quantity, put in-diluted fpirit of ni- 
tre, yields all-on a fudden a large 
quantity of nitrous air of an equal 
degree of firength: but as the fo- 
lution is very tumultuous, anda 
great deal of the pin-duft, together 
with the nitrous acid, is apt to rufh 
out of the phial, I found it at laft 
better to ufé common copper. I 
coil {trong copper wire, neeled {fo as 
to -be flexible, up in fmall curls, 
and fill the phial with them. Thus 
the nitrous -acid, diluted with five 
or fix times its quantity of water - 
being poured in it, finds a large 
