LESSON XII 



THE BLOOD (Concluded) 

 MEDICOLEGAL TESTS FOR BLOOD 



1. Spectroscopic Examination of Blood. Place a few drops of blood 

 in the glass cell provided for this purpose. Dilute it with water until 

 a 0.3 per cent, solution has been obtained. Examine it with a spectro- 

 scope. Identify the and /5 bands. Burn a few crystals of sodium 

 in the flame to produce a distinct Fraunhofer D line. 



Make a sketch showing the precise position and character of these 

 absorption bands. 



FIG. 47. SPECTROSCOPE. 



P, Glass prism; A, collimator tube, showing the slit, S, through which the light is 

 admitted; B, telescope for observing the spectrum. (Howell.) 



Reduce the oxyhemoglobin in the above solution by the addition of 

 a few drops of Stoke's fluid. Repeat the examination. Identify the 

 r band. 



Add to diluted blood a solution of caustic soda or potash, and warm. 

 Reduce, and examine spectroscopically. 



Annotation. Greater concentrations than 0.65 per cent, produce a coalescence 

 of the a and /? bands, while very dilute solutions (0.01 to 0.03 per cent.) give rise to 

 a single band, near the D line. Employ solutions of 0.1 to 0.6 per cent, and use a 

 cell the inner width of which measures 1 cm. 



Stoke's reducing fluid consists of a solution of ferrous sulphate, to which a little 

 tartaric acid has been added. When used, add ammonia till its reaction becomes 

 alkaline. Its color then changes from yellow to dark yellow. 



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