242 Dr. Priestley’s Obfervations on 
the {pace of a meafure and a half. Now fince air is uni- 
verfally depraved by phlogifton, and in this fenfe, I be- 
lieve, by nothing elfe, it is evident, that this black blood 
mult have communicated phlogifton to the air; and con- 
fequently its change of colour from black to a florid red 
muft have been occaftoned by the reparation of phlo- 
gifton from it. 
The next day, when, of courfe, the blood was nearer 
to a ftate of putrefaction, in which every kind of fub- 
ftance, without exception, will injure refpirable air, I put 
a quantity of red blood, tinged in a few places with black, 
which 1 could not eafily feparate from it, to about the fame 
quantity of the fame dephlogifticated air, and fuffered it 
to ftand, without changing, for the fame fpace of time; 
when it was fo little injured, that the meafures abovemen- 
tioned occupied the fpace of only tw o-thirds of a meafure. 
That blood has a power of taking phlogifton from 
air, as well as imparting phlogifton to air, 1 fatisfied my- 
felf by expoflng blood of a very beautiful florid colour 
to nitrous air, inflammable air, and phlogifticated air. 
The two firft mentioned kinds of air were conftderably 
diminiftied by the procefs, which was continued two 
days, during w r hich time the blood had been changed 
live or fix times. 
The nitrous air, by this means, loft a great proportion 
of its power of diminifhing, that is, phlogifticating, 
oommon air. For now tw r o meafures of common air and 
cne of this occupied the fpace of 2^, inftead of i| mea- 
fures. The inflammable air, though ftill inflammable, 
2 was 
