the Attra&ive Powers of Mineral Acids. 49 
111 the former, and its quantity muft always be greater than 
that of the nitrous acid contained in the mineral alkaline bafisj 
becaufe this bails requires for its iaturation more of the marine 
than of the nitrous acid, as we have already feen. 
Yet the nitrous acid, in its turn, decompofes lalt of fylvius 
and common fait, as Mr. marc RAF has fhewn ; but it mud 
always be in greater quantity than the marine, in order to con- 
tain a fufticient quantity of fire for that effeft. To 400 grs. of 
colourlefs 1 pint of nitre, whole fpecific gravity was 1,478, I 
put 60 grs. of common fait, it quickly effervefeed and grew 
red; yet the thermometer rofe but l\ a fign that the marine 
acid had abforbed the greater part of the fire which the nitrous 
had given out, and was thus expelled : befides, in this cafe, 
the fuperior affinity of the nitrous acid to the mineral balls 
haftened the decompolition ; and hence the decompolition hap- 
pens without folution, whereas the marine acid does not de- 
compofe cubic nitre until it has diflblved it, which is worthy 
of notice. This mutual expulfion of the nitrous and marine 
acids by each other is the true reafon why aqua regia may be 
made, as well by adding nitre or nitrous ammoniac to fpirit of 
fait, as by adding common fait or lal ammoniac to fpirit of 
nitre, as Mr. cornette has well remarked. 
Selenite is decompofed neither by the nitrous nor bv the 
marine acids, as Meffi chaptal and cornette have obferved. 
The reafon is evident on the above principles ; it is diffolved by 
neither without the affiftance of heat, and then the folution is 
performed by z fdre'gn heat, and not bv that which thefe acids^ 
give out when they aft without the affiftance of heat. 
Laftly, whenever a vitriolico-neutral lalt, decompofed by 
either the nitrous or marine acid, is evaporated to a certain 
degree, the vitriolic expels thele acids in its turn ; for the free 
Vo l. LXXIIL H part 
