Nessler solution

The sample of glycine must be dry before testing, as traces of impurities generally present in the methyl alcohol give a precipitate with Nessler solution. To carry out the test, o. 1-0.2 g. of dry product is dissolved in 3 to 5 cc. of distilled water containing a few drops of sodium hydroxide solution, and 1 cc. of Nessler solution is added. 

Procedure. A small amount of the solid test material is placed in a micro test tube or a drop of its solution is taken to dryness. A drop or two of a concentrated chloroform solution of hexamine is added and the mixture taken to dryness. The test tube is then immersed to a depth of 1 cm in a glycerol bath preheated to 120 °C. The mouth of the test tube is covered with a disk of filter paper moistened with Nessler solution and the temperature of the bath is increased to 160° C. A brown stain on the reagent paper indicates a positive response. 

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). 

Nessler tubes Cylinders of thin glass, generally graduated, used for comparing turbidities and colours of solutions. 

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. 

Ammonia and ammonium ions in industrial water streams, including waste-water streams, can be determined by either of two methods (ASTM Procedure D1426). In the first, the sample is buffered to a pH of 7.4 and distilled into a solution of boric acid where the ammonia nitrogen is deterrnined colorimetricaHy with Nessler reagents or titrated using standard sulfuric acid. 

A. Standard series method (Section 17.4). The test solution contained in a Nessler tube is diluted to a definite volume, thoroughly mixed, and its colour compared with a series of standards similarly prepared. The concentration of the unknown is then, of course, equal to that of the known solution whose colour it matches exactly. The accuracy of the method will depend upon the concentrations of the standard series the probable error is of the order of + 3 per cent, but may be as high as + 8 per cent. 

B. Duplication method. This is usually applied as the so-called colorimetric titration in which a known volume (x mL) of the test solution is treated in a Nessler cylinder with a measured volume (y mL) of appropriate reagent so that a colour is developed. Distilled water (x mL) is placed in a second Nessler cylinder together with y mL of reagent. A standard solution of the substance under test is now added to the second cylinder from a microburette until the colour developed matches that in the first tube the concentration of the test solution can then be calculated. The standard solution should be of such concentration that it amounts to no more than 2 per cent of the final solution. This method is only approximate but has the merit that only the simplest apparatus is required it will not be discussed further. 

It is advisable, wherever possible, to make a preliminary determination of the concentration of the unknown solution by adding from a burette a solution of the component in known concentration to a Nessler tube containing the reagents diluted with a suitable amount of water until the depth of colour obtained is practically the same as that of an equal volume of the unknown solution also contained in a Nessler cylinder and standing at its side. A series of standards on either side of this concentration is then prepared. 

Discussion. J. Nessler in 1856 first proposed an alkaline solution of mercury(II) iodide in potassium iodide as a reagent for the colorimetric determination of ammonia. Various modifications of the reagent have since been made. When Nessler s reagent is added to a dilute ammonium salt solution, the liberated ammonia reacts with the reagent fairly rapidly but not instantaneously to form an orange-brown product, which remains in colloidal solution, but flocculates on long standing. The colorimetric comparison must be made before flocculation occurs. 

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. 

Standard Solution Into a 50 ml Nessler Cylinder, pipette 2 ml of standard lead solution and dilute with DW to 25 ml. Adjust with dilute acetic acid Sp. (IP) or dilute ammonia solution Sp. (IP) to a pH between 3.0 and 4.0, dilute with DW to about 35 ml and mix. 

Nessler cylinder 1 pair Ferric ammonium sulphate 1.726 g Sulphuric acid (0. 1 N) 10.0 ml Iron-free citric acid (20% w/v) 2.0 ml Thioglycollic acid 0.1 ml Iron-free ammonia solution 20 ml. 

Standard Colour Dilute 2.0 ml of standard iron solution with 40 ml DW in a Nessler cylinder. Add 2 ml of a 20% w/v solution of iron-free citric acid and 0.1 ml of thioglycollic acid, mix, make alkaline with iron-free ammonia solution, dilute to 50 ml with DW and allow to stand for 5 minutes. 

Materials Required Nessler cylinder 1 pair dilute nitric acid (10% w/w of HN03) 10.0 ml silver nitrate solution (5.0% w/v in DW) 1.0 ml. 

Procedure Dissolve the specified quantity for the substance in DW, or prepare a solution as directed in the text and transfer to a Nessler cylinder. Add 10 ml of dilute nitric acid, except when it is used in the preparation of the solution, dilute to 50 ml with DW, and add 1 ml of AgN03 solution. Stir immediately with a glass rod and allow to stand for 5 minutes. The opalescence produced is not greater than the standard opalescence, when viewed transversely. 

Materials Required Doxycyline Hydrochloride 0.30 g oxygen-combustion flask 1 L capacity Nessler cylinder 100 ml zirconyl alizarin solution 5.0ml fluoride standard solution(10ppmF)(dilute... 

Procedure Bum 0.30 g, in three equal portions, by the method for oxygen-flask combustion (BP), using a 1 Litre flask and a separate 20 ml portion of DW as the absorbing liquid for each combustion, shaking the flask vigorously for about 15 minutes and transferring to the same 100 ml Nessler cylinder. Add 5 ml of acid zirconyl alizarin solution to the combined liquids, adjust the volume to 100 ml with DW and allow to stand for 1 hour. 

Ammonium chloride is analyzed by treatment with formaldehyde (neutralized with NaOH) and the product HCl formed is analyzed by titration using an acid-base color indicator such as phenolphthalein. Alternatively, it may be mixed with caustic soda solution and distdled. The distillate may be analyzed for NH3 by titration with H2SO4 or by colorimetric Nesslerization or with an ammonia-selective electrode (APHA, AWWA, WEF. 1995. Standard Methods for the Examination of Water and Wastewater. 19th ed. Washington, DC, American Pubhc Health Association). The presence of ammonia or any other ammonium compound would interfere in the test. The moisture content in NH4CI may be determined by Karl—Fischer method. 

Elemental composition Ca 50.03%, C 14.99%, N 34.98. A measured amount of the compound is hydrolyzed with water. The product CaCOs is filtered, dried and determined by gravimetry. Calcium carbonate or the parent calcium cyanamide may be digested with nitric acid, diluted appropriately, and analyzed for Ca by AA or ICP spectroscopy. The hydrolysis product in solution, ammonia, may be measured by ammonium ion selective electrode, or by colorimetry followed by Nesslerization. 

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. 

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