IDENTIFICATION OF BLOOD-STAINS. 121 



quantity of water dissolve by adding hydrochloric acid carefully. 

 Evaporate the dark-red solution in a vacuum over sulphuric acid. 

 The hydrochloric acid compound of haematoporphyrin crystallizes 

 in brownish-red needles. 



262. Examine the spectrum of the hsematoporphyrin. 



263. Dissolve a few haemin crystals in water by the aid of 

 sodium hydrate and examine the spectrum. 



264. Convert the haemin into haemochromogen by removing 

 the oxygen. Use for this purpose a solution of ferrous sulphate 

 with tartaric acid, the whole being made alkaline with ammonia 

 (Experiment 243). Examine the spectrum. 



265. If hsemin crystals are not at hand, prepare the haemo- 

 chromogen from a dilute solution of blood by first making it 

 alkaline with sodium hydrate, then reducing the haematin thus 

 formed by ammonium sulphid or ammoniacal ferrous tartrate. 



TESTING SUSPECTED STAINS FOR BLOOD. 



The following tests can be used, first on a stain made 

 by drying a drop of blood on a piece of cloth, then upon 

 unknown stains. 



1. Soak a small portion of the stain in a few drops 

 of water on a microscopic slide. If no color is imparted 

 to the liquid, blood is not present or the hemoglobin has 

 been so much decomposed that only the hsemin test will 

 show its presence, or, possibly, the albumin and globulin 

 have been coagulated. 



2. If a red color was seen in the water try the spec- 

 troscopic test. By drying, both haemoglobin and oxy- 

 haemoglobin may be changed into methsemoglobin, which 

 gives a somewhat different spectrum. (Plate IV, 11.) 



Ammonium sulphid reduces this to hemoglobin and 

 shaking with air gives the spectrum of oxyhsemoglobin 

 (Experiments 246 and 247). If these are all obtained the 

 Dresence of blood is proved. 



