ii o Mr. W. Brande’s Chemical Researches on the Blood , 
I accordingly impregnated a piece of calico with decoction 
of oak bark, and afterwards passed it through an aqueous 
solution of the colouring matter of blood. When dry, it was 
of a dirty red colour, nearly similar to that which would have 
been obtained, had no mordant been applied : when however 
an alkaline solution of the colouring matter was employed, 
the colour was equal to that of a common madder red, and as 
far as I have been able to ascertain, it is permanent. 
6. A solution of superacetite of lead was impregnated with 
the colouring matter of the blood. The compound was bright 
red : no spontaneous change took place in it, and on the addi- 
tion of an alkali a white precipitate was formed, the fluid re- 
taining its former tint. 
From this and other experiments, in which it was attempted 
to combine oxide of lead with the colouring of the blood, it 
would appear that there is no attraction between those two 
substances. 
7 . The most effectual mordants, which I have discovered 
for this colouring matter, are some of the solutions of mer- 
cury, especially the nitrate, and corrosive sublimate. 
Ten grains of nitrate of mercury (prepared with heat and 
containing the red oxide), were dissolved in two fluid ounces 
of a solution of the colouring of the blood. After some hours 
a deep red compound was deposited, consisting chiefly of the 
metallic oxide combined with the colouring matter, and a small 
portion of coagulated albumen. The remaining fluid had 
nearly lost its red colour. 
The nitrate of mercury containing the black oxide, produces 
nearly similar effects, excepting that the colour of the com- 
pound is of a lighter red. 
