PREPARATION AND PROPERTIES OF VERDOHEMOCHROMES 463 



(/) Verdohemochrome arises from oxyporphyrin hemichrome by further 

 oxidation in the presence of hydrazine. Cf., however, the footnote on p. 461. 



{g) Magnetochemical investigations of Mellor {lOOG) indicate the presence 

 of one free electron. This proves that the Hnkages are covalent, but the 

 evidence with regard to the valency is not decisive, since verdohemochrome 

 readily forms a fully paramagnetic chloroform-insoluble substance with five 

 free electrons, so that a partial transformation of diamagnetic verdohemo- 

 chrome into this substance may explain the paramagnetism found. 



(/() Libowitzky and Fischer {1731,1732) assume ferric iron since their 

 compound was not readily split by acids. It is uncertain, however, whether 

 their compound was really verdohemochrome; under some conditions at 

 least verdohemochrome is very easily split by acids {cf. below). 



It is evident from a comparison of experiments (a) and {e) that either the 

 ferricyanide or the dithionite reaction must involve an alteration of the tetra- 

 pyrrolic system. Were it not for the inhibition of this reduction by cyanide, 

 it would be certain that the ferricyanide alters the valency of the iron, while 

 the dithionite reacts with the tetrapyrrolic system. It will be seen below 

 that the action of cyanide may perhaps be explained, not as reaction with 

 •^ iron, but on the basis of the tetrapyrrolic system. 



On the whole we believe that the evidence in favor of the ferrous 

 state of verdohemochrome is stronger. 



Verdohematin is obtained as a black powder on removal of the 

 pyridine by washing solid verdohemochrome or its chloroform solu- 

 tion with water. Apparently oxidation occurs in this process. Verdo- 

 hematin can be dissolved in dilute sodium carbonate or phosphate 

 buffer, giving a dark olive solution which absorbs light in the red but 

 shows no distinct absorption bands. On cautious reduction with a 

 small amount of dithionite the green verdoheme is obtained. Its 

 absorption band in the red is indistinct. On passing coal gas through 

 this solution a band at 610 mpi appears, in addition to a band at 

 665 m^ (carboxy verdoheme). 



In dilute sodium carbonate, verdohematin undergoes an irreversible 

 alteration, even in the absence of oxygen {16S8). The product is now no 

 longer reconvertible to verdohemochrome and is easily split to biliverdin by 

 dilute acetic acid {cf. also 1731). Reduction yields a green compound which 

 has also been obtained from biliverdin by introduction of iron and is probably 

 its ferrous iron complex. The ease of conversion of verdohemochrome into 

 biliverdin in this manner provides additional evidence against the assumption 

 of a carbon-closed ring in verdohemochromes and supports the semiacetal 

 formula suggested below. 



Verdohematin combines with native globin giving the olive-green 

 verdohemiglobin (indistinct absorption in the red, ab.sorption bands 

 at 532 and 505 m^). With a small amount of dithionite the solution 



