5Q6 PHYSIOLOGICAL CHEMISTRY 



Basic Lead Acetate Solution. 1 This solution possesses the following 

 formula: 



Lead acetate 180 grams. 



Lead oxide (Litharge) no grams. 



Distilled water to make 1000 grams. 



Dissolve the lead acetate in about 700 c.c. of distilled water, with boiling. 

 Add this hot solution to the finely powdered lead oxide and boil for one- 

 half hour with occasional stirring. Cool, filter and add sufficient dis- 

 tilled water to the filtrate to make the weight i kg. 



Benedict's Solutions. 2 First Modification. Benedict's modified 

 Fehling solution consists of two definite solutions a copper sulphate 

 solution and an alkaline tartrate solution, which may be prepared as 

 follows: 



Copper sulphate solution = 34.65 grams of copper sulphate dissolved 

 in water and made up to 500 c.c. 



Alkaline tartrate solution = 100 grams of anhydrous sodium carbon- 

 ate and 173 grams of Rochelle salt dissolved in water and made up to 

 100 c.c. 



These solutions should be preserved separately in rubber-stoppered 

 bottles and mixed in equal volumes when needed for use. This is done 

 to prevent deterioration. 



Second Modification. Benedict has further modified his solution 

 and has succeeded in obtaining one w r hich does not deteriorate upon 

 long standing. It has the following composition: 



Copper sulphate , 17.3 grams. 



Sodium citrate 173 .o grams. 



Sodium carbonate 100 . o grams. 



Distilled water to make i liter. 



With the aid of heat dissolve the sodium citrate and carbonate in 

 about 600 c.c. of water. Pour (through a folded filter paper if neces- 

 sary) into a glass graduate and make up to 850 c.c. Dissolve the 

 copper sulphate in about 100 c.c. of water and make up to 150 c.c. 

 Pour the carbonate-citrate solution into a large beaker or casserole and 

 add the copper sulphate solution slowly, with constant stirring. The 

 mixed solution is ready for use and does not deteriorate upon long 

 standing. 



Benedict's Sugar Reagent. 3 



Copper sulphate (crystallized) 18.0 grams. 



Sodium carbonate (crystallized, one-half the weight of the 



anhydrous salt may be used) 200.0 grams. 



Sodium or potassium citrate 200.0 grams. 



Potassium thiocyanate 125.0 grams. 



Potassium ferrocyanide (5 per cent solution) 5.0 c.c. 



Distilled water to make a total volume of 1000.0 c.c. 



1 Indican determination, p. 542. 



2 Benedict's modifications of Fehling's test, pp. 27 and 417. 



3 Quantitative determination of sugar, p. 522. 



