Nessler’s solution

Salts of Millon s Base.—Suspend a little of the base in water and shake with a dilute solution of potassium iodide. The solution turns alkaline. The brown precipitate is the same as that produced by Nessler s solution in tests for ammonia. 

Nessler s solution is conveniently prepared by dissolving 62 5 grams of potassium iodide m 250 c.c. water and adding to a cold, saturated solution of mercuric chloride until a faint permanent precipitate is obtained. Add 150 grams of potassium hydroxide in 150 o.e. of water, and finally a sufficient quantity of mercuric chloride solution to cause a slight, permanent, yellow precipitate. Dilute to one litre. 

A better procedure is to employ the technique described under the man-ganese(II) nitrate-silver nitrate reagent in reaction 9 below. A drop of Nessler s solution is placed on the glass knob of the apparatus. After the reaction is complete, the drop of the reagent is touched with a piece of drop-reaction or quantitative filter paper when a yellow colouration will be apparent. 

For general laboratory measurements water of specific conductance of about 1 X 10 ohm cm.- at 18° is satisfactory this can be obtained by distilling good distilled water, to which a small quantity of permanganate or Nessler s solution is added. A distilling flask of resistance glass is used and the vapor is condensed either in a block-tin condenser or in one of resistance glass. If corks are used they should be covered with tin foil to prevent direct contact with water or steam. 

Note the change in color of the barium hydroxide solution of the second receiver and explain. Towards the end, disconnect the delivery tube and pass the gas for a minute into a test tube which contains a few cubic centimeters of distilled water. Determine the pH of the solution by the addition of a few drops of universal indicator. Confirm the presence of ammonia with Nessler s solution. The Nessler test is also applied to a solution known to contain ammonia, and to a sample of distilled water. 

Another and neater way of separating the crystals from the adherent mother liquor is to pack two balanced 12-ml centrifuge tubes each half full with glass wool, distribute the crystal mush equally between the two tubes so that they remain balanced, and centrifuge for a few minutes (see Chapter III). This salt is used in preparing Nessler s solution, a sensitive reagent for ammonia, and is worth keeping. It may, however, be used for the preparation to follow. 

Nessler s solution or reagent contains potassium tetraiodomercurate(II) and is available commercially although it can be prepared in the laboratory easily. When the reagent is added to a dilute ammonium salt solution, the liberated ammonia reacts forming an orange brown colloid ... 

Prepare Nessler s solution by dissolving SO g of mercury(II) iodide and 35 g KI in water (see text). Cool and add, slowly with stirring, 80 g NaOH in 350 cm water and make up to 500 cm Allow to stand in the dark for 3-4 days and use the supernatant. Commercially available solution can be used. 

Ammonia and ammonium salts can be readily detected, in very minute traces, by the addition of Nessler s solution, which gives a distinct yellow coloration in the presence of the least trace of ammonia or ammonium salts. 

Mcrcuryill) iodide, HgL. Scarlet (to 126 C) or yellow substance (HgC L solution plus KI or Hg plus I2)- Forms complex iodides with excess iodide (Nessler s reagent). 

Nessler s reagent An alkaline solution of Hglj in KI used for detecting and estimating ammonia (brown colour or precipitate formed). 

Ammonia present in very small quantities in solution may be estimated by comparing the intensity of colour produced with Nessler s reagent (p. 439) with standard colours, using a simple form of colorimeter called a Nessleriser . 

Nessler s reagent (for free ammonia) dissolve 50 g of K1 in the least possible amount of cold water add a saturated solution of HgClj until a very slight excess is indicated add 400 mL of a 50% solution of KOH allow to settle, make up to a liter with water, and decant. 

The reaction with Nessler s reagent [an alkaline solution of potassium tetraiodomercurate(II)] may be represented as ... 

If necessary, dilute the sample to give an ammonia concentration of 1 mg L 1 and fill a 50 mL Nessler tube to the mark. Prepare a series of Nessler tubes containing the following volumes of standard ammonium chloride solution diluted to 50 mL 1.0,2.0,3.0,4.0,5.0, and 6.0 mL. The standards contain 0.01 mg NH3 for each mL of the standard solution. Add 1 mL of Nessler s reagent to each tube, allow to stand for 10 minutes, and compare the unknown with the standards in a Nessler stand (Section 17.4) or in a BDH Nesslerimeter. This will give an approximate figure which will enable another series of standards to be prepared and more accurate results to be obtained. 

In caustic soda or caustic potash solution, mercury(TI) iodide forms complex salts, Na2Hgl4 and K2Hgl4, respectively. Alkaline solution of this complex in excess potassium hydroxide is known as Nessler s reagent, used to analyze ammonia. The reaction of Nessler s reagent with ammonia may be written as ... 

The compound is prepared and marketed only in aqueous solution. It is used mostly as a disinfectant and a topical antiseptic. Also, it is used to make Nessler s reagent for analyzing ammonia, and as an analytical reagent for alkaloids. 

Reaction to Ammonium Ion (Nessler s Reagent). Introduce 5 ml of a 0.1 N mercury(II) nitrate solution heated to 80 °C into a 50-ml beaker and add 5 ml of a 0.1 A potassium iodide solution. Cool the mixture, let the precipitate settle, pour off the solution, and wash the precipitate three times with cold water by decantation. Add 0.2 g of potassium iodide dissolved in 5 ml of water to the precipitate. When the latter dissolves, pour in 3 ml of a 10% sodium hydroxide solution and transfer the contents into a dark jar. 

Ammonium Salts. — Carefully add 2 cc. of fuming sulphuric acid, by drops, to 30 cc. of water, and add aqueous solution (1 6) of potassium hydroxide to alkalinity on now adding 10 to 15 drops of Nessler s reagent, at most a pale-yellow, but in no case a brownish-red, color or precipitate may develop. 

Ammonium Compounds. — On adding 1 cc. of Nessler s reagent to a solution of 10 gm. of sodium carbonate in 50 cc. of water, no change should be observed. 

Ammonium. Hie solution of 3 gm. of sodium chloride in 20 re. of water should not bo changed in appearance on the addition of Nessler s reagent. 

The well known Nessler s reagent for ammonia is a solution of mercuric oxide in aqueous potassium iodide. 

A 50 mg sample of each ground fabric was introduced into a 50 mL Erlenmeyer flask, and 20-30 mL of deionized/distilled water was added. After approximately 15 minutes, each solution was filtered through ashless filter paper into a 100 mL volumetric flask. A 2 mL aliquot of Nessler s Reagent (APHA, Fisher Scientific Company) was... 

Ammonia is readily detectable in air in the range of a few parts per million by its characteristic odor and alkaline reaction. Specific indicators, such as Nessler s reagent (Hgk in KOH), can detect ammonia in a concentration of 1 ppm. For the quantitative determination of ammonia in air, synthesis gas and aqueous solutions, these methods can be used74 Acidimetry and Volumetric Analysis By Absorption, Gas Chromatography, Infrared Absorption, Thermal Conductivity Measurement, Electrical Conductivity Measurement, Measurement of Heat of Neutralization, and Density Measurement (for aqueous ammonia). 

Ammonium Dissolve 1 g of sample in 90 mL of water, and slowly add 10 mL of a freshly boiled and cooled solution of 1 10 sodium hydroxide. Allow the mixture to settle, then decant 20 mL of the supernatant liquid into a color comparison tube, dilute to 50 mL with water, and add 2 mL of Nessler s reagent. Any color does not exceed that produced by 10 xg of ammonium (NH4) ion in 48 mL of water and 2 mL of the sodium hydroxide solution. 

Mercuric-Potassium Iodide TS, Alkaline (Nessler s Reagent) Dissolve 10 g of potassium iodide (KI) in 10 mL of water, and add slowly, with stirring, a saturated solution of mercuric chloride until a slight red precipitate remains undissolved. To this mixture add an ice-cold solution of 30 g of potassium hydroxide (KOH) in 60 mL of water, then add 1 mL more of the saturated solution of mercuric chloride. Dilute with water to 200 mL. Allow the precipitate to settle, and draw off the clear liquid. A 2-mL portion of this reagent, when added to 100 mL of a 1 300,000 solution... 

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