1 16 Chemical Researches on the Blood, &fc. 



portion of alkali, which modifies the action of the re-agents 

 commonly employed, but which is readily separated by 

 electrical decomposition. 



To ascertain whether iron exists in the serum of the 

 blood, one pint was evaporated to dryness in a crucible, 

 and gradually reduced to a coal, which was incinerated and 

 digested in muriatic acid, to which a few drops of nitric 

 acid were added ; some panicles of charcoal remained un- 

 dissolved ; the solution was saturated with ammonia, 

 which afforded a copious precipitation of phosphate of lime, 

 accompanied with slight traces only of oxide of iron. 



SECTION V. 

 Some Erperiments upon the Coagulum of Blood. 

 Mr. Hatchett's valuable researches on the chemical con- 

 stitution of the varieties of coagulated albumen, have 

 shown that that substance varies but little in its properties, 

 whether obtained from the crassamentum of the blood, or 

 from washed muscular fibre, or other sources; but that 

 the proportion of earthy and saline matter is different in 

 the different varieties*. 



It will also be remarked, on referring to the dissertation 

 which I have just quoted, that the ashes obtained by in- 

 fcineraling the coal left after the destructive distillation of 

 albumen, did not contain any appreciable proportion of iron. 

 Assuming the existence of iron in the colouring matter 

 of the blood, I made the following experiments upon the 

 crassamentum of that fluid. 



Two pints of blood were collected in separate vessels. 

 The one portion was allowed to coagulate spontaneously ; 

 the other was stirred for half an hour with a piece of wood, 

 so as to collect the coagulum, but to diffuse the principal 

 part of the colouring matter through the serum. These 

 two portions of coagulum were now dried, in a water-bath, 

 and equal weights of each reduced in a platina crucible to 

 the state of '^oal, which afterwards was incinerated. The 

 ashes were digested in dilute nitro-muriatic acid, and the 

 solution saturated with liquid ammonia, in order to preci- 

 pitate the phosphate of lime as well as any iron which 

 jni^ht have been present. 



The precipitates were collected, dried, and treated with 

 dilute acetic acid, by which they were almost entirely dis- 

 solved, some very minute traces only of red oxide of iron 

 remaining, the quantity of which was similar in both cases, 

 and so small as pearly to have escaped observation^ 



• Phil. Trans, 1800, p. 384. 



