IRON COMPOUNDS IN ANIMAL AND VEGETABLE CELLS. 187 
and Amblystoma), whether hardened or fresh, yield the 
reaction in a few minutes. Such compounds are of too limited 
a range of distribution to affect the value of the reagent in 
making a distinction between the iron compounds. On 
hemoglobin and myo-hzematin (myo-hzemoglobin) the reagent 
has not the slightest action. I have kept mixtures of the 
reagent with solutions of hemoglobin and myo-hemoglobin 
for more than a year at a temperature of 55° C., and in no case 
have I found that iron was liberated from these compounds as 
sulphide. I have, moreover, mounted in the glycerine and 
sulphide mixture on the slide finely powdered hemoglobin 
which had been coagulated in alcohol, and applied heat to the 
preparation for weeks without once obtaining the iron in an 
inorganic form. When, therefore, in preparations of animal 
tissues which have been hardened in alcohol one obtains with 
the glycerine and sulphide method after a time an iron reac- 
tion, it may reasonably be concluded that the iron so demon- 
strated is not derived from hemoglobin in the tissues. One 
may not, however, exclude hematin as a possible source of iron, 
for although hemoglobin in all forms will not yield its iron to 
ammonium hydrogen sulphide, the latter readily liberates the 
iron of hematin, and from a solution of hematin in am- 
moniated alcohol or in dilute ammonia, into which hydrogen 
sulphide has been passed, part of the iron at ordinary tempera- 
tures, but the whole at 50° C., is precipitated as ferrous sulphide, 
in a few days.! Even in a solution of hematin in ammoniated 
alcohol, if kept for several days at the temperature of the room, 
1 The compound formed from the hematin in this process of liberating the 
iron is neither hematoporphyrin nor bilirubin. With yellow nitric acid it gives 
a play of colours in which violet, faint red, and yellow successively appear, the 
mixture finally becoming colourless, and it yields an absorption spectrum like 
that of bilirubin. It is insoluble in ether, and soluble in chloroform and hot 
alcohol. The other properties of this compound are now under investigation. 
It has one special claim to interest in that it is formed from hematin by a 
method very much less drastic in its effects than those in which strong sul- 
phuric acid or bromine in glacial acetic acid is used to form hematoporphyrin 
or bilirubin (Nencki and Sieber, ‘Monatsh, fiir Chemie,’ vol. ix, p. 115, 
1888), 
