Monobasic Salts Dibasic Salts 



KH2PO4 NaH2PO4«H20 pH 



6.4 

 6.6 

 6.8 

 7.0 



7.2 

 7.4 

 7.6 

 7.8 

 8.0 



Mix the monobasic and dibasic salts, dissolve in 700 ml. of hot 

 distilled water, cool to room temperature, and dilute to 1 liter in a 

 volumetric flask. 



BARBITAL (VERONAL) BUFFER 



pH 6.8 - 9.2 

 Reference: Recalculated from J. B.C. 87 33 (1930) 



Stock Solution: 0.500M Sodium Veronal (also called Disodium Barbital, 

 Barbital Soluble) 

 Prepared by weighing out 51.545 g. of Veronal Sodium (Merck Powder) 

 and dissolving in enough distilled water to make 500 ml. The powder, as 



it comes in the bottle, may be used directly without drying. 



] 

 Buffers : 



To make 500 ml. of O.IM Veronal Buffer pipette 100 ml. of the 0.500M 

 stock solution into a 500 ml. volumetric flask, add the volume of l.OOOM^HCl 

 specified below, and dilute to the mark with distilled water. 



tpH ml. l.OOON HCl 



6.8 45.80 



7.0 43.30 



7.2 40.25 



7.4 36.05 



7.6 31.30 



7.8 25.53 



8.0 19.85 



■•"It is difficult to prepare buffers of a pH lower than 8.8. This is due 

 to tlie ppt. of barbituric acid at low pHs . 



*IIere, for better accuracy, ten times as much O.IOOON HCl may be 

 used instead. 



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