486 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Estimation of Haemoglobin. 



Most of the methods which have been devised for the estimation 

 of haemoglobin depend upon the comparison of the colour of blood 

 with that of carefully prepared standard colours. These standard 

 colours are either various shades of red painted on paper, or coloured 

 glass, or they are a standard colour in solution made from a suitably 

 diluted normal blood. The standard solution may be blood, treated 

 with carbon monoxide to give carboxy haemoglobin, diluted to a fixed 

 amount. 



The amount of haemoglobin may also be determined by ascertaining 

 the oxygen capacity of the blood and indirectly by an enumeration of 

 the red blood corpuscles if each corpuscle contains the normal amount. 



A. Colorimetrically. 



(1) Tallquisfs Method. 



In this method the colour of a drop of blood is matched against a 

 series of red spots on paper. These spots have colours varying from 

 light to dark red and represent percentages from 10 to 100. They 

 are arranged in a series and by their side is a circular opening in the 

 paper. A drop of blood from the finger is touched with a piece of 

 white blotting-paper, or filter paper, and allowed to diffuse through the 

 paper so as to give an even stain. As soon as the blood is dry, the 

 stain is viewed through the openings in the paper against the 

 standards and the colours are matched. The percentage of haemo- 

 globin in the blood corresponds with that of the standard. As the 

 standards do not show every unit a very close approximation cannot 

 be made, e.g. the blood stain may be deeper in colour than the 95 

 per cent, standard, but paler than the 100 per cent. one. The method 

 gives good average results, but is not very accurate. 



(2) Von FleisMs Method. 



In this method an apparatus (Fig. 59) consisting of a mirror (R\ a coloured 



glass wedge (K) and a circular 

 cell (G) with two partitions (a, 

 a') is used. The mirror has 

 a white reflecting surface (S) 

 and is adjusted to send light 

 through the coloured wedge 

 and through the two com- 

 partments of the cell. One of 

 the compartments of the cell 

 is filled with water ; in the 

 other compartment is placed 

 a small amount of water; 

 20 cmm. of blood are col- 

 lected from the finger in a 

 specially graduated capillary 

 pipette and ejected into the 

 water in this compartment, 

 which is then completely filled 

 with water. The volume of 

 the compartment is such that 

 the blood is diluted 100 times. 

 The colours are observed and the wedge is moved by means of a screw (T) 

 until the colours match. The graduated scale (P) on the instrument gives the 

 percentage of haemoglobin. 



