488 Demonstration of Iron in Chromatin. [Apr. 30, 



tion to the plates (which were rolled hot) experimented npon in 

 Table VIII, it will be noticed that, in several instances with soft cast 

 steel and hard cast steel, the wrought iron did not assume the electro- 

 positive position until two or three hours after immersion in the nitric 

 acid. Subsequently the iron assumed its normal position, and became 

 during the long remaining period of the observations electro-positive 

 to the steels, with a considerable and increasing E.M.F., showing 

 that the wrought iron was becoming gradually very much leas passive 

 than the steels. In the case of the soft Bessemer and soft Siemens 

 plates, Table VIII, we have also a similar instance of these peculiar 

 and temporary interchanges and variations of relative passivity which 

 are not easily accounted for. In the case of the tungsten steel, 

 Table VI, the wrought iron was steadily in the electro-negative posi- 

 tion, hence in the latter instance showing the wrought iron to be 

 permanently more passive than the tungsten steel. 



A reference to the experiments on the wrought iron and various 

 steel plates, on Table VIII, shows that the E.M.F. between the 

 passive wrought iron and the various soft steels, which contained 

 less percentage of combined carbon, in circuit in cold nitric acid 

 sp. gr. 1'42, was very considerably less than the E.M.F. under similar 

 conditions between the wrought-iron plates and the different hard 

 steels having a higher percentage of combined carbon. The latter 

 results, therefore, demonstrate the interesting circumstance that 

 steels, of a higher percentage of combined carbon are more passive 

 than those of a lower percentage of combined carbon. It will be 

 observed that the wrought iron was also electro-positive to most of the 

 steels, whether of a higher or lower percentage of combined carbon, 

 which shows that wrought iron may be regarded as generally less 

 passive than steels. 



III. " On the Demonstration of the Presence of Iron in 

 Chromatin by Micro-chemical Methods." By A. B. 

 MACALLUM, M.B., Ph.D. Communicated by Professor H. N. 

 MARTIN, F.R.S. Received April 23, 189 J. 



(Abstract.) 



The method of isolating what is called chromatin by tbehistologist 

 yields compounds of fairly stable composition called nucleins, some 

 of which have been shown to contain iron (Bnnge and Zaleski). My 

 observations on haematopoiesis in Amphibia led me to the conclusion 

 that the chromatin, from which the hemoglobin of the hsematoblasts 

 is derived, is an iron-holding compound. Other observations indicated 

 that the conclusion could, possibly, be made of general application, 

 i.e., that iron is present in the chromatin of every cell, animal and 



