BLOOD ANALYSIS 



reaction, stays in solution. The tube is finally shaken vigorously (covering the 

 end of the tube with the finger) and the contents filtered through a small filter, or, 

 better still, centrifuged for one or two minutes. 



One c.c. of the filtrate or the clear supernatant fluid obtained on centrifugal- 

 ization is withdrawn, put into the plain test-tube, and heated carefully over the 

 naked flame. The contents of the tube are boiled until all but 2 or 3 drops of the 

 solution is evaporated. One-half c.c. of the 10 per cent sodium carbonate solution 

 is then added and the tube heated again until the contents are concentrated to 

 a small volume equal to about 2 or 3 drops. The color of the fluid changes from 

 yellow to deep red or reddish brown and the reaction is completed. 



Three or 4 drops of distilled water are added and the tube warmed gently. The 

 contents are then transferred to the graduated tube of the hemoglobinometer. 

 The boiling tube is rinsed several times with water (using only 3 or 4 drops at a 

 time). The tube is warmed with each rinsing before transferring the contents to 

 the graduated tube. The volume of fluid is then made up to the mark 50 on the 

 scale. 



FIG. 82. APPARATUS FOR EPSTEIN'S SUGAR METHOD. 



The color of the resulting solution is compared with that of the two standard 

 tubes, A and B which accompany the instrument. (A solution of picramic acid 

 of the proper strength, prepared as described on p. 280, may be used as a standard.) 

 If it is darker than standard A (representing 0.05 per cent of sugar) and lighter 

 than standard B (representing o.i per cent), the first standard is used for com- 

 parison. In either case the solution in the graduated tube is diluted gradually 

 with water (just as is usually done in hemoglobin estimations) until the colors 

 match. 



The percentage of sugar in the blood is then computed thus: Using the lighter 

 standard A the figure on the scale, divided by 1000 represents the percentage of 

 sugar in the blood. For example, the tube reads 86; then the result is 



Q A 



= 0.086 per cent 

 i ceo 



When Standard B is used for comparison, the figure on the scale is multiplied 

 by 2 and divided by 1000. For example, the tube reads 73; then the percentage 

 of sugar is 



0.146 per cent 



1000 



