Dr. Wells's Observations and Experiments , &c. 417 
thought, that the mild volatile alkali, which has been supposed 
by chemists to superabound with phlogiston, can yet attract it 
from blood. It appears to me, however, unnecessary to bring 
any further arguments of this kind against the opinion of Dr. 
Priestley, since the following experiments will, I expect, be 
thought sufficient to shew, in opposition to what is taken for 
granted by him in the whole of his inquiry, that the alteration 
induced upon the colour of blood, both by common air and the 
neutral salts, is altogether independent of any change effected 
by them upon its colouring matter. 
I infused a piece of black crassamentum of blood in dis- 
tilled water, and immediately after covered the containing 
vessel closely, to prevent the access of air. Having obtained 
by this means a transparent solution of the red matter of blood, 
nearly free from serum and coagulable lymph, I exposed a 
quantity of it to the open air, in a shallow vessel, and poured 
an equal quantity into a small phial, which was then well 
closed. When the first portion of the solution had been ex- 
posed to the air for several hours, I decanted it into a phial, of 
the same size and shape as that which contained the second 
portion, and having added to it as much distilled water as was 
sufficient to compensate the loss it had suffered by evapo- 
ration, I now compared the two together, and found them to 
be exactly of the same colour, with regard both to kind and 
degree. I afterwards poured two other equal quantities of the 
red solution into two phials of the same size and shape. To 
one I added a little of a solution of nitre in water, and to the 
other as much distilled water. Upon comparing the two mix- 
tures together, I found that they also possessed precisely the 
same colour. Lastly, I cut a quantity of dark crassamentum 
