CHEMICAL RESEARCHES ON THE ANIMAL FLUIDS. 183 



perfectly green by transmitted light. In its other habitudes it 

 nearly resembles the muriatic solution. 



E, The solution of the colouring matter in oxalic acid is of ^[^^^, "^^^^^Jj'^' 

 a brighter red than those hitherto noticed ; that in citric acid tartaric. 

 is very similar to the acetic solution, and with tartaric acid the 

 compound somewhat inclines to scarlet. All these solutions 

 exhibit the green hue, to which I have so often alluded, in a re- 

 markable degree. 



6. Ejects of Alkalis on the colouring Principle of the Blood, 

 The caustic and the carbonated alkalis form deep red solu- Action of the 

 tions of this substance, which are extremely permanent. colourin" prio^ 



1. Solutions of pure potash, and of the subcarbonate, take ciple. 

 up a large proportion of the colouring matter of the blood. 

 The intensity of the colour of this solution, when concentrated, 

 is such, that it appears opaque, unless viewed in small masses, or 

 in a diluted state, when it is of a bright red colour. 



2. In soda and its subcarbonate the solution has more of a 

 crimson hue, which colour is extremely bright in its concen- 

 trated state. 



3. The solution in liquid ammonia approaches nearer to 

 scarlet than that in which the fixed alkalis are employed. 



4. When these alkaline solutions are supersaturated with 

 muriatic acid, or with dilute sulphuric acid, they acquire a 

 colour nearly similar to the original solutions in those acids, 

 which have been above described. 



5. Nitric acid, added in small quantities, or even to satura- 

 tion of the alkaline menstruum, heightens the colour of the 

 three compounds ; but vi^hen there is a slight excess, a tint of 

 orange is produced, which soon passes into bright yellow. 



6. The alkaline solutions may be evaporated nearly to dry- 

 ness without losing their red colour ; during the evaporation of 

 the ammoniacal solution, the alkali flies off, and a brown red 

 solution of the colouring matter in water remains. 



Having ascertained the above facts respecting the colouring Examination 

 principle of the blood, 1 next proceeded to examine how far it of the affinities 

 was susceptible of entering into those combinations which are ing matter, 

 peculiar to other varieties of colouring matter. 



These experiments I shall detail in the order in which they 

 were made. 



1. Some 



