1S13.] Chemical Properties of Animal Fluids. 197 



water, which is phosphate of lime, but in so minute a quantity 

 as not to be appreciable. 



I incinerated 20 grammes (400 grains) of colouring matter, 

 till the charcoal was completely destroyed, and obtained - 25 

 grammes (5 grains) of ashes having a yellowish red colour. By 

 an accurate analysis, I found it composed of 



Oxide of iron 50*0 



Subphosphate of iron 7-5 



Phosphate of lime with a small") 



■ c • > 6'0 



quantity or magnesia J 



Pure lime 20*0 



Carbonic acid, and loss 16*5 



100-0 



But this phosphate of iron was not, in all probability, con- 

 tained in the colouring matter, not even in the ashes : it has 

 evidently been a product of the analytic process. It is produced 

 in like manner when oxide of iron and phosphate of lime are 

 dissolved together in an acid, and afterwards precipitated with 

 caustic ammonia. Part of the lime remains in solution, and 

 the iron seizes upon its phosphoric acid. 



But as one mode of argument will hardly suffice to overturn 

 a thcoiy maintained by chemists of such eminence as Fourcroy 

 and Vauquclin, and for the support of which they have brouo-ht 

 forward many positive facts, I have made a number of experi- 

 ments with a view of throwing light on this subject, and have 

 not met with a single one, which did not appear in contradic- 

 tion to the opinion of these celebrated analysts. Some of these 

 experiments I shall now relate. 



(A.) The prussiates, as we have already seen, produce no 

 effect on the colouring matter of the blood ; and yet they detect, 

 after 24 hours, the least quantity of any ferruginous salt added 

 to it, having the red oxide of iron for its basis. — (B.) A watery 

 solution of colouring matter, mixed with gallic acid, acquires a 

 beautiful red colour, but the acid produces no precipitate. By 

 adding to the solution of colouring matter one or two drops of a 

 dilute solution of tannin, the liquor becomes of a beautiful red, 

 without any precipitate appearing. But if, on the contrary, the 

 solution of tannin be concentrated, it precipitates the colourimr 

 matter, and gives it a pale red colour. None of these effects 

 ■ em to prove the presence of a salt with the base of oxide of 

 iron. — fC.) The aqueous solution of colouring matter, mixed 

 with solution of barytes, is not precipitated: at the end of 24 

 hours a small quantity of phosphate of barytes is found at the 

 bottom of the vessel, and the liquor has assumed a green colour 

 by the action of the alkaline base. Lime-water produces no 



