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to my firfl lefolution, under an absolute neceffity of 
giving a name to this kind of air mvfelf. When I 
hrft began to fpeak and write of it to my friends, I 
happened to diftinguiih it by the name of nitrous air, 
becaufe I had procured it by means of fpirit of nitre 
only; and though I cannot fay that I altogether lik£ 
the term, becaufe this air is not got from all the me- 
tals by the fame fpirit, neither myfelf nor any 
of my friends, to whom I have applied for the pur* 
pofe, have been able to hit upon a better ; fo that 
I am obliged, after all, to content myfelf with it. 
I have found that this kind of air is readily pro- 
cured from iron, copper, brafs, tin, filver, quickfil- 
ver, bifmuth, and nickel, by the nitrous acid only, 
and from gold and the regulus of antimony by aqua 
regia. The circumftances attending the folution of 
each of thefe metals are various, but hardly worth 
mentioning, in treating of the properties of the air 
which they yield, which, from what metal foever it 
is extracted, has, as far as I have been able to ob- 
ferve, the very fame properties. 
One of the moft confpicuous properties of this kind 
of air is the great diminution of any quantity of com- 
mon air with which it is mixed, attended with a tur- 
bid red, or deep orange colour, and a considerable 
heat. The fmell of it, alfo, is very Strong, and re- 
markable, but very much refembling that of fmoking 
fpirit of nitre. 
The diminution of a mixture of this and common 
air is not an equal diminution of both the kinds, 
which is all that Dr. Hales could obferve, but of the 
common air chiefly, though not wholly. For If orte 
meafure of nitrous *air be put to two tneafures of 
E e 2 common 
