the Djffblutkn cf Metals In Acids* ' 369 
properties of this compound, they would probably have be- 
flowed on it the appellation of aqua regin 
SECTION THIRD* 
The change of properties communicated to the mixture of vitriolic 
and nitrous acids by phlogiflication . 
20. The above-defcribed compound acid may be phlogifti- 
eated in different methods, of which I (hall mention three. 
1 ft, By digefting the compound acid with fulphur by means 
of the heat of a water-bath, the liquor diflolves the fulphur 
with effervefcence, lofes its property of yielding white fumes ; 
and if the quantity of fulphur be fufficient, and if the heat 
applied be long enough continued, it exhibits red nitrous 
vapours, and a flumes a violet colour. 
2dly, If, inftead of diffolving nitre in concentrated vitriolic 
acid, this acid be impregnated with nitrous gas, or with nitrous 
vapour, by making this gas or vapour pafs into the acid, this 
compound will be phlogifticated, as it contains not the entire 
nitrous acid, but only its phlogifticated part, or element, the 
nitrous gas, without the proportion of pure air neceifary to 
conftitute an acid. This impregnation of oil of vitriol with 
nitrous gas or nitrous vapour was firft defcribed, and fome 
of the properties of the impregnated liquor noticed, by Dr. 
Priestley. See Experiments and Gbfervations on Air, Voh 
III. p. 129 and 217. 
^dlv, By fubftituting nitrous ammoniac inftead of nitre in 
the mixture with oil of vitriol. 
21. The compound prepared by any of thefe methods, but 
efpecially by the firft and fecond, differs confiderably in its 
Vol. LXXX. C c c properties 
