CHAPTER VI 



MICROCHEMICAL METHODS FOR BLOOD ANALYSIS 



The microchemical methods for the estimation of sugar, urea, 

 creatinine, etc., in the blood have become important as aids in 

 diagnosis. Folin and his co-workers have been conspicuous in 

 developing satisfactory methods of analysis. The most import- 

 ant of these are given here. 



For the final estimation of nitrogen, the well known Nessler 

 method is used, modified to meet the conditions of these specific 

 methods. 



The readings are made in a Duboscq colorimeter. If the 

 students are not familiar with the use of this instrument it 

 should be demonstrated by the instructor. 



Folin 's Modified Nessler 's Reagent (Laboratory Manual, 

 1921). "This reagent is essentially a solution of the double 

 iodid of mercury and potassium (HgI 2 ,2KI) containing sodic 

 or potassic hydrate. A stock solution of the double iodid is best 

 prepared as follows : 



"Transfer 150 g. of potassium iodid and 110 g. of iodin to a 

 500 c.c. Florence flask; add 100 c.c. of water and an excess of 

 metallic mercury 140 g. to 150 g. Shake the flask continuously 

 and vigorously for 7 to 15 minutes or until the dissolved iodin 

 has nearly all disappeared. The solution becomes quite hot. 

 When the red iodin solution has begun to become visibly pale, 

 though still red, cool in running water and continue the shaking 

 until the reddish color of the iodin has been replaced by the 

 greenish color of the double iodid. This whole operation usually 

 does not take more than 15 minutes. Now separate the solution 

 from the surplus mercury by decantation and washing with 

 liberal quantities of distilled water. Dilute the solution and 

 washings to a volume of two liters. If the cooling was begun 



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