PRACTICAL EXERCISES 



75 



a considerable time. Examine some of the blood (after dilution) 

 with the spectroscope. Two bands, almost in the position of the 

 oxyhaemoglobin bands, are seen; but no change is caused by the 

 addition of ammonium sulphide, since carbonic oxide haemoglobin is 

 a more stable compound than oxyhaemoglobin. 



(d) Methcemoglobin. Put some blood into a test-tube, add a few 

 drops of a solution of ferricyanide of potassium, and heat gently. On 

 diluting a well-marked band will be seen in the red. On addition of 

 ammonium sulphide this band disappears; the oxyhaemoglobin bands 

 are seen for a moment, and then give place to the band of reduced 

 haemoglobin (Fig. 13, p. 51). 



(e) Acid HcBmatin. To a little diluted blood add strong acetic acid 

 and heat gently. The colour becomes brownish. The spectrum 

 shows a band in the red between C and D, not far from the position 

 of the band of methaemoglobin. The addition of a drop or two of 

 ammonium sulphide causes no change in the spectrum, and this is a 

 means of distinguishing acid haematin from methaemoglobin.. If more 

 ammonium sulphide be added, 



haematin will be precipitated 

 when the acid solution has been 

 rendered neutral, and a urther 

 addition of ammonium sulphide 

 or sodium hydroxide will cause 

 the haematin to be again dis- 

 solved, a solution of alkaline 

 haematin being formed. This 

 in its turn may be reduced by 

 an excess of ammonium sul- 

 phide, and the spectrum of 



haemochromogen may be ob- 

 tained (Fig. 13, p. 51). 



Since the watery solution 

 of acid haematin obtained as 

 above is usually somewhat tur- 

 bid, a solution in acid ether is 

 sometimes employed for spec- 

 troscopic examination. Add to 

 a little undiluted defibrinated 

 blood about half its volume of 

 glacial acetic acid, and then not 

 less than an equal volume of 



Specfrosco/ie 

 Solution. 

 



Fig. 21. Spectroscopic Examination of 

 Blood-Pigment, 



ether. Mix well, pour off the ethereal extract and examine it with the 

 spectroscope, diluting, if necessary, with ether and glacial acetic acid. 

 It shows a strong band in the red somewhat farther from the D line 

 than the methaemoglobin band. On dilution, thre^ additional fainter 

 bands may be seen. 



(/) Alkaline Hcematin. To diluted blood add strong acetic acid and 

 warm gently for a few minutes. Then, when the spectroscopic ex- 

 amination of a sample shows that acid haematin has been formed, 

 neutralize with sodium hydroxide. A brownish precipitate of haematin 

 is thrown down, which dissolves in an excess of sodium hydroxide, 

 giving a solution of alkaline haematin (or alkali haematin). 



Or add sodium hydroxide to blood directly, and warm for a couple of 

 minutes after the colour has changed decidedly to brownish-black. 

 The spectrum of alkaline haematin is a broad but ill-defined band just 

 overlapping the D line, and situated chiefly to the red side of it (Fig. 13). 

 The solution should be shaken up with air before being examined, as 



