Reagents for Phosphorus Lab

Check with the instructor and your classmates to see what has been made and what needs to be made. These solutions should be made using acid-washed glassware.

Sulfuric Acid Solution

Carefully add 300 mL concentrated H2SO4 solution to 600 mL water. When solution is cool fill to 1L with DI water

Sodium Hydroxide, NaOH 1N

Dissolve 40 g NaOH in 600 mL DI water with constant stirring. After solution is cool dilute to 1L with DI water

Sulfuric Acid, H2SO4 5N

Add about 300 mL of DI water to a 500 mL volumetric flask and add 70 mL concentrated H2SO4. Mix well. When the temperature of the mixture is back to room temperature, dilute to 500 mL with DI water.

Potassium antimonyl tartrate solution

Dissolve 1.3715 g potassium antimonyl tartrate, K(SbO)C4H4O6·½H2O, in DI water and dilute to 500 mL. Store in a glass stoppered bottle. The solution is good for six months. Note: This compound is also known as antimony potassium tartrate, C8H4K2O12Sb2·3H2O.

Ammonium molybdate solution

Dissolve 20 g ammonium molybdate, (NH4)6Mo7O24· 4H2O, in DI water and dilute to 500 mL. Store in a glass stoppered bottle.

Stock phosphate solution, 50mg/L phosphorus

Dissolve 0.2195 g potassium dihydrogen phosphate (KH2PO4), dried at 105°C, in water and dilute to 1L. (Preserve with 2 drops of chloroform--maybe not.) Good for 3 months. Store in a fridge.

1mL = 50m g PO4-P

Standard phosphate solution, 2.5 mg/L P

Dilute 50 mL stock phosphate solution to 1L w/ DI water. Solution good for a week. Store in a fridge.

1mL = 2.5m g PO4-P

Reference (independent) stock solution, 25mg/L

Obtain potassium dihydrogen phosphate (KH2PO4), from another source than was used for preparation of the stock solution. Dissolve 0.1098 g in about 500 mL of DI water in a 1L volumetric flask. Dilute to 1L with DI water, mix well and store in a fridge.

Ascorbic acid solution, 0.01 M

Stable only for about one week. Dissolve 1.76 g ascorbic acid in 100 mL distilled water.

Combined reagent

This is only good for about four hours. Make fresh as needed. Use solutions at room temperarature. Add ingredients in the order listed and swirl to mix after adding each ingredient. Combine:

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