63 



til the spectrum is as distinct as it can be made. Hold the 

 spectroscope so that the red is at the left of the field. Dip a 

 wire into some water, and then into some salt or sodium car- 

 bonate, and hold it in a flame of a fish-tail burner. Note the 

 change in the spectrum. 



258. Arrange the apparatus with the aid of a demonstra- 

 tor, so that the spectroscope, gas-flame and substance to be 

 examined, are in their proper relations. Half fill the vial or 

 test-tube with defibrinated blood. Nothing can be seen until 

 the blood is properly diluted. Continue diluting until two 

 bands of oxyhemoglobin appear in the spectrum. Note their 

 position, and which one disappears first when the solution is 

 diluted far enough. 



259. Add a drop or two of ammonium sulphide solution 

 or Stokes' fluid to reduce the oxyhemoglobin. Note the re- 

 sult. Stokes' fluid is prepared by 2 grams ferrous sulphate 

 and 3 grams of tartaric acid. These are mixed and preserved 

 dry for use. When required, add 100 cc. of water and enough 

 ammonia to make slightly alkaline. 



260. Pass some illuminating gas through some blood for 

 a considerable time. Examine with a spectroscope. Add a 

 drop or two of ammonium sulphide or Stokes' Fluid., Com- 

 pare this with 257. 



