66 POISONS : THEIR EFFECTS AND DETECTION. [§ 41. 
with great facility. The best way to steep the spots in the solution is 
to scrape the spot off the fabric, and to digest it in about a cubic centi¬ 
metre of the borax solution, which must not exceed 40° ; the coloured 
solution may be placed in a little glass cell, with parallel walls, -5 centi¬ 
metre broad and -1 deep, and submitted to spectroscopic examination, 
either by the ordinary spectroscope or by the micro-spectroscope ; if 
the latter is used, a very minute quantity can be examined, even a 
single drop. A better solvent is Riegler’s reagent, to be described later. 
In order to interpret the results of this examination properly, it will 
be necessary to be intimately acquainted with the spectroscopic appear¬ 
ances of both ancient and fresh blood. 
§ 41. Spectroscopic Appearances of Blood. —Fresh blood defibrin- 
ated, filtered, and examined in a test tube or in a suitable absorption 
cell by a prism spectroscope shows, when diluted sufficiently with water, 
two absorption bands, the one near the sodium line well defined, the 
maximum shadow being at wave length 578-1 ; the other in the green 
with somewhat fluffy edges, therefore less definite in the green, the 
centre of the band being at 541-7 ; this two-banded spectrum is that 
of oxyhemoglobin. The spectrum is graphically represented in fig. 1, 
taken from J. Formanek’s paper. 1 
On exposure of the same solution to air, new bands make their 
appearance ; these new bands are those of methaemoglobin ; the older 
the solution, the more the bands of methaemoglobin tend to intensify, 
the more those of oxyhaemoglobin fade. The spectrum is, however, 
with blood weeks or even months old, always a mixture of oxyhaemo- 
globin and methaemoglobin ; the wave lengths of the two methaemo- 
globin bands’ centres are respectively 634, and a weak band in the 
green 500-8 (see fig. 2). 
By adding ammonium sulphide to blood the spectrum of haemoglobin 
(fig. 3) is obtained ; it shows a weak absorption band (619-8) and a 
broad, somewhat diffuse band (554-7). 
Oxyhaemoglobin solutions treated with alkalies suffer change ; the 
oxyhaemoglobin is separated into haematin and an albuminous body. 
The haematin is soluble in strong soda lye, and shows a single band in 
alcoholic solution, which is situated about A 598-8 (see fig. 6). If this 
alkaline solution of haematin is now treated with a reducing substance, a 
third colouring substance makes its appearance, called by Hoppe-Seyler, 
who discovered it, by the name of haemochromogen ; this shows two 
absorption bands very similar to haemoglobin, but both bands are shifted 
towards the violet end of the spectrum (A 559-1 and A 529-2) (fig. 7). 
By utilising the properties of hydrazin, which dissolves the red 
blood vcorpuscles, and at the same time is a powerful reducing agent, 
1 “ Ueber die Absorption Spectra dos Blutfarbstoffe ” Zeil. f. anal. Chemie, 
1901, 505. 
