96 METHODS FOR THE ANALYSIS OF BLOOD 



ment may be formed in the course of a week or so. If this happens, 

 decant the clear solution into another bottle. 



3. Molybdate Phosphate Solution. Transfer to a liter beaker 35 

 gms. of molybdic acid and 5 gms. of sodium tungstate. Add 200 

 c.c. of 10 per cent sodium hydroxide and 200 c.c. of water. Boil 

 vigorously for twenly to forty minutes so as to remove nearly the 

 whole of the ammonia present in the molybdic acid. Cool, dilute 

 to about 350 c.c. and add 125 c.c. of concentrated (85 per cent) 

 phosphoric acid. Dilute to 500 c.c. 



Procedure. Heat a beaker of water to vigorous boiling. 

 Transfer 2 c.c. of the tungstic acid blood filtrate to a blood sugar 

 test-tube, and to two other similar test-tubes (graduated at 25 c.c.) 

 add 2 c.c. of standard sugar solution containing respectively 0.2 

 and 0.4 mg. of dextrose. To each tube add 2 c.c. of the alkaline 

 copper solution. The surface of the mixtures must now have 

 reached the constricted part of the tube. If the bulb of the tube 

 is too large for the volume (4 c.c.) a little, but not more than 0.5 

 c.c. of a diluted (1:1) alkaline copper solution may be added. If 

 this does not suffice to bring the contents to the narrow part, the 

 tube should be discarded. Test-tubes having so small a capacity 

 that 4 c.c. fills them above the neck should also be discarded. 

 Heat the tubes in a boiling water bath for six minutes. Then 

 transfer them to a cold water bath and let cool, without shaking, 

 for two to three minutes. Add to each test-tube 2 c.c. of the 

 molybdate phosphate solution. The cuprous oxide dissolves 

 rather slowly if the amount is large but the whole, up to the amount 

 given by 0.8 mg. of dextrose, dissolves easily within two minutes. 

 When the cuprous oxide is dissolved, dilute the resulting blue 

 solutions to the 25 c.c. mark, insert a rubber stopper, and mix. 

 It is essential that adequate attention be given to this mixing 

 because the greater part of the blue color is formed in the bulb of 

 the tube. At least five minutes after mixing make the color com- 

 parison in the usual manner. 



Calculation. The depth of the standard (in mm.) multiplied 

 by 100 and divided by the reading of the unknown gives the sugar 

 content, in mg., per 100 c.c. of blood. 



Remarks. The two standards given representing 0.2 and 0.4 

 mg. of glucose are adequate for practically all cases. They cover 

 the range from 70 to nearly 400 mg. of glucose per 100 c.c. of blood. 



