[ 496 ] 
filled the Flask, and gone off with an Explofion equal 
to the Firing of a large Piftol 5 and fometimes indeed it 
has burft the Flask. The fame Effect ^produced from 
Spirit of Sea Salt, as from Oil of Vitriol 5 but as the 
Acid of Sea-Salt is much lighter than that of Vitriol, 
there is no Neceflity to add the Water in this Experi- 
ment. 
Thofe who are not much acquainted with Che- 
mical Philofophy, may think it very extraordinary, 
that, from a Mixture of cold Subfiances, which, both 
conjunctly and feparately, are uninflammable, this very 
inflammable Vapour fhould be produced. In order 
to folve this, it may not be improper to premife, 
that Iron is compounded of a fulphureous as well as 
a metallic Part. This Sulphur is fo fixed, that, after 
heating the Iron red hot, and even melting it ever 
fo often, the Sulphur will not be dilengdged there- 
from : Bur, upon the Mixture of the vitriolic Acid, 
and by the Heat and Ebullition which are almoft in- 
ftantly produced, the metallic Part is diffolved, and 
the Sulphur, which before was intimately connected 
therewith, being difengaged, becomes volatile. This 
Heat and Ebullition continue, till the vitriolic Acid 
is perfectly faturated with the metallic Part of the 
Iron ; and the Vapour, once fired, continues to 
flame, until, this Saturation being perfected, no more 
of the Sulphur flics off. 
I have heretofore mentioned, how confiderably 
perfectly dry Air conduces to the Succefs of thefe 
Experiments j but we have been lately informed, by 
an Extract of a Letter, that Abbe Nolet was of Opi- 
nion, that they would fucceed in wet Weather, pro- 
vided the Tubes were made of Glafs tinged blue with 
Z aider. I have procured Tubes of this fort, but, 
after 
