246 THE RED BLOOD CORPUSCLES. [CH. X. 



297. In two test-tubes place 2 or 3 cc. of solutions of oxy- 

 haemoglobin and CO-haemoglobin of the same depth of colour. 

 Fill the test-tubes with water and mix well. Note that the CO- 

 haemoglobin takes on a well-marked carmine tint, whilst the 

 oxyhaemoglobin turns }^ellow. This simple test, which can only be 

 seen on extreme dilution, rapidly serves to distinguish the two 

 compounds. 



298. Methaemoglobin. To 5 cc. of water add four drops 

 of defibrinated blood. To the strong solution of oxyhaemoglobin 

 thus formed add two drops of a saturated solution of potassium 

 ferricyanide. The colour of the solution changes to a chocolate- 

 brown. Examine with the spectroscope : there is visible a promi- 

 nent band in the red, with its centre at about A 630. There is 

 marked absorption of the blue end of the spectrum. Dilute with 

 an equal bulk of water and examine again : two faint bands appear 

 in the green in the position of the bands of oxyhaemoglobin. 



299. Dilute the solution of met haemoglobin thus obtained 

 with another volume of water. Treat 5 cc. of this with two or 

 three drops of ammonium sulphide and examine immediately. The 

 colour changes to a red : the absorption band in the red disappears, 

 and the spectrum of oxyhaemoglobin is seen. Warm the solution 

 to 50 C. and allow it to stand for a short time (possibly with the 

 addition of another drop or two of the reducing reagent). The two 

 bands give place to the single band of reduced haemoglobin. Shake 

 with air : oxyhaemoglobin is reformed. 



300. Take a few cc. of defibrinated blood in a test-tube, add 

 an equal quantity of water and warm to 50 C. to lake the blood. 

 Oxygenate the solution by shaking with air, adding a drop 

 of caprylic alcohol to prevent undue frothing. To the solution 

 thus obtained add an equal bulk of saturated potassium ferri- 

 cyanide. Mix by giving one shake, and then hold the tube at 

 rest in an oblique position for a short time. Note the bubbles of 

 gas (oxygen) that are evolved. 



NOTES. i. Oxyhaemoglobin is converted into methaemoglobin by the 

 action of oxidising reagents, such as ferricyanides, nitrites, chlorates, and 

 permanganates, and in the body, by the action of many aromatic substances, 

 such as phenol. 





