492 Prof. D. F. Harris and Dr. H. J. M. Creighton. [May 10, 



investigation it has been shown* that soluble Prussian blue is decolorised by 

 native and derived proteins, and although this action is inappreciable at room 

 temperature at tbe end of several hours, and even at 60° C. requires an hour 

 or more for completion, at 100° C. the decolorisation takes place very 

 rapidly. The decolorisation of the blue is due to the formation of a complex 

 with the protein, which is broken down by hydrochloric acid with return of 

 the blue colour. In the light of this investigation, the fading of the colour 

 from mixtures of press juice and soluble Prussian blue at 100° C. must be 

 attributed to some action due to the presence of protein, and not to the action 

 of the reductase. 



(d) The Reduction of Iron Salts by the Press Juice of Liver.- — A few experi- 

 ments were undertaken to see whether the press juice from liver was 

 capable of bringing about the reduction of ferric salts. 



To a dilute solution of ferric chloride, 3 c.c. of two-day-old press juice were 

 added, and the mixture kept at 40° C. for 20 minutes. The protein substances 

 were then filtered off, and a few drops of potassium ferricyanide added to the 

 brown coloured filtrate. On the addition of the potassium ferricyanide, a 

 green-blue precipitate which rapidly turned deep blue was formed, indicating 

 the presence of iron in the ferrous condition. Pure press juice gave no 

 coloration with potassium ferricyanide. In a control experiment, where a 

 ferric chloride solution was warmed with 3 c.c. of press juice which had been 

 boiled, no blue coloration was observed on the addition of potassium 

 ferricyanide. 



It will be seen from these experiments that ferric salts are readily reduced 

 to the ferrous condition by the reductase of liver. 



(e) The Reduction of Nitrates. — In a recent investigation, Kastle and 

 Elvovef have shown that various inorganic nitrates are reduced to nitrites 

 by the action of aqueous extracts of certain plants. This suggested the 

 possibility of the reduction of nitrates being brought about by the reductase 

 in liver press juice. Accordingly, a number of experiments was undertaken 

 with this end in view. 



In each of two test-tubes, 20 c.c. of two-day-old press juice (prepared 

 March 27) were placed. One of these tubes was placed in boiling water for 

 five minutes. It was then cooled and diluted to its original volume with 

 distilled water. To each tube 20 c.c. of a pure solution of sodium nitrate, 

 containing 5 grm. of the salt, were simultaneously added, and both tubes 

 tightly corked and shaken. The tubes were then placed in a thermostat 

 at 50° C. for an hour and a half, during which time they were frequently 



* Creighton, H. J. M., 'Trans. Nova Scotia Inst. Sci.,' 1911—1912, vol. 13 (2), p. 61. 

 t Kastle, J. H., and E. Elvove, ' Amer. Chem. Journ.,' 1904, vol. 31, p. 606. 



