which Metals acquire by being calcined . . 379 
vessel to fly off, and give place to the air of the atmosphere ; 
which happened spontaneously from the different specific gra- 
vities of the two vapours. 
The vessel containing the solution of the zinc was now laid 
upon its side, and 10148 grains of aqua kali puri were intro- 
duced by a crooked funnel into the globe B, being the quan- 
tity sufficient to saturate 1000 grains of vitriolic acid, as before 
determined. Then the tube D was hermetically sealed, and 
the whole weighed. The vessel was then raised, so that the 
globe A was undermost ; this was done very gradually, so 
that the aqua kali puri was gradually added to the solution of 
the zinc : when a little was poured in, the vessel was brought 
into an horizontal position again, and shaken a little ; this 
was repeated until the whole of the aqua kali puri was poured 
in. The zinc was thus precipitated in the form of a calx. 
It was suffered to stand for forty-eight hours : no alteration of 
the gravity took place, therefore nothing had entered through 
the glass to give additional weight to the zinc in order to 
calcine it. 
The next step was to open the tube, which was done under 
water, and in an atmosphere of the same heat in which it was 
sealed, to wit, 57 0 of Fahrenheit's thermometer. The air 
was neither diminished nor increased, none of the water being 
driven into the apparatus by the weight of the atmosphere, 
and none being thrown out. On heating the globe B, so as 
to drive out some of the air, it was found to be of the same 
purity, nearly, as that of the atmosphere, being tried by the 
application of nitrous air produced from solution of mercury. 
The weight, therefore, which the calx had gained, arose 
neither from any substance passing through the glass, nor 
