PRACTICAL EXERCISES 63 



of the absorption bands with regard to the D line should always be 

 noted. The dark lines in the solar spectrum are due to thj absorp- 

 tion of light of a definite range of wave-lengths by metals in a state 

 of vapour in the sun's atmosphere, and of course no dark lines are 

 seen in the spectrum of a gas-flame. Half fill a test-tube with 

 defibrinated blood. Fasten it vertically in a clamp in front of the 

 flame and examine it with the spectroscope, holding the latter in one 

 hand with the slit close to the test-tube, and focussing the eyepiece 

 with the other. Or arrange the spectroscope, test-tube and gas-flame 

 on a stand as in Fig. 14. Nothing can be seen till the blood is 

 diluted. Pour a little of the blood into another test-tube, and go on 

 diluting till, on focussing, two bands of oxyJuzmoglobin are seen in 

 the position indicated in Fig. 8. Draw the spectrum ; then dilute 



FIG. 14. SPECTROSCOPIC EXAMINATION OF BLOOD-PATENT. 



still more, and observe which of the bands first disappears. Now 

 put 5 c.c. of the blood into another test-tube, and dilute it with 

 four times its volume of water. Take 5 c.c. of this dilution, and 

 again add four times as much water, and so on till the solution is 

 only faintly coloured. Note with what degree of dilution the bands 

 disappear. Then examine each of the solutions with the spectro- 

 scope and draw its spectrum. 



(ft) Make a solution of blood which shows the oxyhaemoglobin 

 bands sharply. Add some ammonium sulphide solution to reduce 

 the oxyhaemoglobin. Heat gently to about body-temperature. A 

 single, ill-defined band now appears, occupying a position midway 

 between the oxyhaemoglobin bands, and the latter disappear. This 

 is the band of reduced hemoglobin (Fig. 8). 



(c) Carbonic Oxide H&moglobin. Pass coal-gas through blood for 



