208 METHODS FOR THE ANALYSIS OF BLOOD 



or otherwise so conducted that danger of carbon monoxide poison- 

 ing is avoided). Compare in colorimeter against standard 1 per 

 cent carbon monoxide hemoglobin solution. 



Apparatus and Reagents. 0.1 c.c. pipette (calibrated to con- 

 tain 0.1 c.c.). 



10 c.c. volumetric flask. 



Dilute ammonia solution (4 c.c. strong ammonia in 1 liter 



of water). 

 Colorimeter. 



Standard hemoglobin solution (same as in Haldane's 

 Method). 



Suggestions. 1. A standard made up to contain a 20 per cent 

 solution of blood, having an oxygen capacity of 18.5 per cent, 

 is kept in the ice-chest, saturated with CO (illuminating gas). 

 From this a 1 per cent solution for routine use may be made. 

 Seal in the cork with paraffin. This concentrated solution will 

 keep for months. 



2. A standard 1 per cent solution for routine use is made up 

 in 100 and 200 c.c. lots and kept sealed in a bottle which should 

 be protected from light. With ordinary care, if kept in the ice- 

 chest and protected from light, it will keep for weeks. At room 

 temperature it keeps for about a week. 



3. In making standards or dilutions always use the specified 

 dilute ammonia solution. 



HEMOGLOBIN DETERMINATION 



Method of Cohen and Smith 1 



Principle. The hemoglobin of blood is transformed into acid 

 'hematin and this solution compared in a colorimeter with a 

 standard solution of acid hematin. 



Procedure. From a freely flowing source of blood, 0.02 c.c. 

 is measured by means of a calibrated Sahli pipette into 6 c.c. of 

 0.1 N hydrochloric acid. The blood pipette is rinsed out by draw- 

 ing the acid solution into it several times. Blood very low in hemo- 

 globin may require a double sample, i.e., 0.04 c.c. of blood in 6 c.c. 

 1 Cohen and Smith: Jour. Biol. Chem., 1919, 39, 489. 



