1 8 6 Analyfis of the Air. 
Prom the little quantity of air which i s 
obtained by the diftillation of that very fixt 
body fea- fait in Experiment 71. in compa- 
rifon of what arifes from nitre and Sal Tar- 
tar, we fee the reafon why it will not go 
off with an explofive force, like thofe when 
fired. And at the fame time we may hence 
ofaferve, that the air included in nitre and 
Sal Tartar , bears a confiderable part in their 
explofion. For fea- fait contains an acid 
fpirtt as well as nitre > and yet that without 
a greater proportion of air does not qualify 
it for explofion, tho' mixed like nitre in the 
compofition of gun-powder, with fulphur 
and charcoal. 
Mr. Boyle found that Aqua-fortis poured 
on a ftrong folution of fait of tartar did not 
fhoot into fair cryftals of falt-petre, till it 
had been long expofed to the open air 5 
whence he fufpefted that the air contribu- 
ted to that artificial production of falt-petre. 
And fays, “ whatever the air hath to do in 
* c this Experiment, we have known fuch 
<c changes made in fome faline concretes, 
* c chiefly by the help of the open air, as 
“ very few would be apt to imagine” Vol. 
1. p. 302. and Vol. 3. p. 80. And Chy- 
mills obferve* that when the effential falts 
of 
