REAGENTS AND SOLUTIONS 645 



Sulphuric Acid, Two-thirds Normal. 1 Dilute 35 gm. of concen- 

 trated c.p. sulphuric acid to a liter. Standardize against alkali of 

 known strength. 



Sulphuric-Phosphoric Acid Digestion Mixture. 2 To 50 c.c. of 

 5 per cent, copper sulphate solution add 300 c.c. of 85 per cent phos- 

 phoric acid and mix. Add 100 c.c. of concentrated sulphuric acid 

 free from the least trace of ammonia and mix. Keep well protected to 

 prevent absorption of ammonia from the air. 



Suspension of Manganese Dioxide. 3 Made by heating a o.- per 

 cent solution of potassium permanganate with a little alcohol until it is 

 decolorized. 



Tanrefs Reagent. 4 Dissolve 1.35 grams of mercuric chloride in 

 25 c.c. of water, add to this solution 3.32 grams of potassium iodide 

 dissolved in 25 c.c. of water, then make the total solution up to 60 c.c. 

 with distilled water and add 20 c.c of glacial acetic acid to the mixture. 



Tincture of Iodine. Dissolve 70 gram's of iodine and 50 grams of 

 potassium iodide in i liter of 95 per cent alcohol. 



Topfer's Reagent. 5 Dissolve 0.5 gram of di-methylaminoazobenzene 

 in 100 c.c. of 95 per cent alcohol. 



Tropaeolin OO. 6 Dissolve 0.05 gram of tropseolin 00 in 100 c.c. 

 of 50 per cent alcohol. 



Uffelmann's Reagent. 7 Add a 5 per cent solution of ferric chloride 

 to a i per cent solution of carbolic acid until an amethyst-blue color is 

 obtained. 



Uranium Acetate Solution. 8 Dissolve about 35.0 grams of uranium 

 acetate in i liter of water with the aid of heat and 3-4 c.c. of glacial 

 acetic acid. Let stand a few days and filter. Standardize against a 

 phosphate solution containing 0.005 gram of f^O& per cubic centimeter. 

 For this purpose dissolve 14.721 grams of pure air-dry sodium am 1 

 monium phosphate (NaNH 4 HP04+4H 2 0) in water to make a liter. 

 To 20 c.c. of this phosphate solution in a 200 c.c. beaker add 30 c.c. 

 of water and 5 c.c. of sodium acetate solution (see above) and 

 titrate with the uranium solution to the correct end reaction as indi- 

 cated in the method proper, page 572. If exactly 20 c.c. of uranium 

 solution are required i c.c. of the solution is equivalent to 0.005 gram 



"^Preparation of protein-free blood nitrates, p. 276 



2 Determination of nitrogen, p. 277 and 507. 



3 Kriiger and Schmidt's method, p. 533 . 



4 Tanret's test, p. 103. 



5 Topfer's method, p. 177. 



6 Test for free acid, p. 158. 



7 Uffelmann's reaction, p. 173. 



8 Phosphate determination, p. 568. 



