A database about Preparation of Laboratory Reagents. A Project of SCIENCE Pakistan

Nesslers reagent

Dissolve 10gms. of potassium iodide in 10mls. of ammonia-free water, adding saturated mercuric chloride solution (60gms. / litre) in small quantities at a time with shaking, until a slight permanent precipitate is formed, then adding 80ml. of 9M sodium hydroxide solution and diluting to 200ml.Allow to stand overnight and decant the clear liquid.

Nesslers reagent has been described as a solution which is about 0.09M in potassium mercuri-iodide and 2.5M in potassium hydroxide.

An alternative method is to dissolve23gms. of mercuric iodide and 16gms. of potassium iodide in ammonia-free water and make up the volume to 100ml; add 100ml. of 6M sodium hydroxide. Allow to stand for 24hrs. and decant the solution from any precipitate that may have formed, the solution should be kept in the dark.

Another method that reacts promptly and consistantly is to dissolve 143 g of sodium hydroxide in 700 ml water. Disolve 50 g of red mercuric iodide and 40 g of potassium iodide in 200 ml water. Pour the iodide solution into the hydroxide solution, and dilute with water to 1 liter. Allow to settle, and use the supernatant liquid.
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