Acidity , the Dccompoftion of Water, and Ph Jeff on. 323 
liquor, befides having the tafte of nitrous acid, diftblved filver ; 
and when neutralized by vegetable alkali and {lowly evapo- 
rated, afforded well-formed crvffals of common nitre* 
Thefe, Sir, are all the trials I have made with the liquors 
produced in your experiments. They pretty clearly prove the 
acid generated to be the fame, whether the dephlogifticated air 
was procured from red precipitate of mercury, from minium, 
or from manganefe, and that this acid is the nitrous acid. It 
is not quite fo clear why the liquor and fediment in § iv. gave 
no ftronger marks of the prefence of nitrous acid ; but it is 
evident, that the acid had united itfelf to the iron, if not to 
the tin, of the vellel employed : and I find, that when nitrous 
acid is fully faturated with iron by being boiled with it, and 
fixed alkali is added, this mixture l'ubmitted to diftillation, with 
the addition of concentrated vitriolic acid, yields no red va- 
pours, and very little fmell of nitrous acid. 
1 
I remain, &c. 
W. WITHERING. 
Birmingham, 
February 22, 1788. 
TO THE REV. DR. PRIESTLEY. 
DEAR SIR, 
I HAVE examined the green liquor which I received from 
you, with a view to determine the two points you wilhed prin- 
Vol. LXXVIII. X x cipally 
