92 VETEEINAEY TOXICOLOGY 



depends on the character of the absorption spectrum of 

 carbon monoxide blood, which may be observed in a 

 dilution of 1 of defibrinated blood in 1,000. This test may 

 therefore be applied to blood post-mortem, or used for air 

 by agitating the suspected sample with normal defibrinated 

 blood of the above strength. The absorption spectrum 

 of carboxyhsemoglobin is similar to that of oxyhsemoglobin, 

 viz., two bands in the yellow, but displaced a little to the 

 right. The difference is in the fact that reducing agents 

 such as ferrous salts, but better ammonium sulphide, reduce 

 oxyhsemoglobin, with fusion of the two bands into one, 

 larger and indistinctly outlined, whilst reduction does not 

 alter the carbon monoxide blood spectrum. 



A chemical method of detection consists in passing the 

 suspected gas over gently warmed pure iodine pentoxide. 

 Even with very small proportions of carbon monoxide 

 iodine is liberated which is absorbed in potassium iodide 

 solution, and recognised by the starch or other of the well- 

 known tests for iodine. The reaction is not absolutely 

 conclusive, since such hydrocarbons as acetylene (which is 

 also present in coal gas) behave similarly. 



