Standard Ammonium Solution

Ammonium Standard Solution (10 pig NH4 in 1 mL) Dissolve 296.0 mg of ammonium chloride (NH4C1) in sufficient water to make 100.0 mL, and mix. Transfer 10.0 mL of this solution into a 1000-mL volumetric flask, dilute to volume with water, and mix. 

Ammonium Standard Solution, 849 Ammonium Sulfanilate TS, 850 Ammonium Sulfate, 28 Ammonium Sulfide TS, 850 Ammonium Thiocyanate, 0.1 N, 856 Ammonium Thiocyanate TS, 850 Amyl Acetate, 510 1-Amyl Alcohol, 454, (S3)66 Amylase, 130, (S3)18 a-Amylase, 132, 786 P-Amylase, 132, 786 Amyl Butyrate, 454, 510, (S3)66 Amyl Caprylate, 454 Amylcinnamaldehyde, 454 a-Amylcinnamaldehyde, 454, 605,... 

The prescribed quantity of the substance to be examined is dissolved in 14 ml of water R in a test tube, made alkaline if necessary by the addition of dilute sodium hydroxide solution R and diluted to 15 ml with water R. To this solution 0.3 ml of alkaline potassium tetraiodomercurate R is added. A standard is prepared by mixing 10 ml of ammonium standard solution (1 ppm NHfi R with 5 ml of water R and 0.3 ml of alkaline potassium tetraiodomercurate R. Stopper the test tubes. After 5 min, any yellow color in the test solution is not more intense than that in the standaid. 

The method is generally applicable when other modes of esterification are either slow, inefficient, or likely to cause isomerisation it is, however, time-consuming and expensive. Small quantities of acid impurities are sometimes produced, hence it is advisable to wash the ester with saturated sodium bicarbonate solution. The silver salt can usually be prepared by dissolving the acid in the calculated quantity of standard ammonium hydroxide solution and... 

Another reducing titrant is ferrous ammonium sulfate, Fe(NH4)2(S04)2 6H2O, in which iron is present in the +2 oxidation state. Solutions of Fe + are normally very susceptible to air oxidation, but when prepared in 0.5 M 1T2S04 the solution may remain stable for as long as a month. Periodic restandardization with K2Cr20y is advisable. The titrant can be used in either a direct titration in which the Fe + is oxidized to Fe +, or an excess of the solution can be added and the quantity of Fe + produced determined by a back titration using a standard solution of Ce + or... 

Ammonium acetate solutions formed by neutralizing acetic acid using ammonium hydroxide are essentially neutral. Thus, these solutions are suitable for standardization of electrodes, and for use as titration standards. Solutions must be used while fresh, however, as they become acidic on standing. 

Table 5. American National Standard Specifications for Photographic-Grade Ammonium Thiosulfate Solution...

Discussion. When a solution of an orthophosphate is treated with a large excess of ammonium molybdate solution in the presence of nitric acid at a temperature of 20-45 °C, a precipitate is obtained, which after washing is converted into ammonium molybdophosphate with the composition (NH4)3[P04,12Mo03]. This may be titrated with standard sodium hydroxide solution using phenolph-thalein as indicator, but the end point is rather poor due to the liberation of ammonia. If, however, the ammonium molybdate is replaced by a reagent containing sodium molybdate and quinoline, then quinoline molybdophosphate is precipitated which can be isolated and titrated with standard sodium hydroxide ... 

Pipette 25 mL nickel solution (0.01 M) into a conical flask and dilute to 100mL with de-ionised water. Add the solid indicator mixture (50mg) and 10 mL of the 1M ammonium chloride solution, and then add concentrated ammonia solution dropwise until the pH is about 7 as shown by the yellow colour of the solution. Titrate with standard (0.01 M) EDTA solution until the end point is approached, then render the solution strongly alkaline by the addition of 10 mL of concentrated ammonia solution, and continue the titration until the colour changes from yellow to violet. The pH of the final solution must be 10 at lower pH values an orange-yellow colour develops and more ammonia solution must be added until the colour is clear yellow. Nickel complexes rather slowly with EDTA, and consequently the EDTA solution must be added dropwise near the end point. 

The following sections are concerned with the use of standard solutions of reagents such as silver nitrate, sodium chloride, potassium (or ammonium) thiocyanate, and potassium cyanide. Some of the determinations which will be considered strictly involve complex formation rather than precipitation reactions, but it is convenient to group them here as reactions involving the use of standard silver nitrate solutions. Before commencing the experimental work, the theoretical Sections 10.74 and 10.75 should be studied. 

Pipette 25 mL of the standard 0.1 M silver nitrate into a 250 mL conical flask, add 5mL of 6M nitric acid and 1 mL of the iron(III) indicator solution. Run in the potassium or ammonium thiocyanate solution from a burette. At first a white precipitate is produced, rendering the liquid of a milky appearance, and as each drop of thiocyanate falls in, it produces a reddish-brown cloud, which quickly disappears on shaking. As the end point approaches, the precipitate becomes flocculent and settles easily finally one drop of the thiocyanate solution produces a faint brown colour, which no longer disappears upon shaking. This is the end point. The indicator blank amounts to 0.01 mL ofO.lM silver nitrate. It is essential to shake vigorously during the titration in order to obtain correct results. ... 

Better results are obtained by transferring 25.0 mL of the diluted hydrogen peroxide solution to a conical flask, and adding 100 mL 1M(1 20) sulphuric acid. Pass a slow stream of carbon dioxide or nitrogen through the flask, add 10 mL of 10 per cent potassium iodide solution, followed by three drops of 3 per cent ammonium molybdate solution. Titrate the liberated iodine immediately with standard 0.1M sodium thiosulphate in the usual way. 

With the exception of iron(II) and uranium(IV), the reduced solutions are extremely unstable and readily re-oxidise upon exposure to air. They are best stabilised in a five-fold excess of a solution of 150g of ammonium iron(III) sulphate and 150 mL of concentrated sulphuric acid per litre [approximately 0.3M with respect to iron] contained in the filter flask. The iron(II) formed is then titrated with a standard solution of a suitable oxidising agent. Titanium and chromium are completely oxidised and produce an equivalent amount of iron(II) sulphate molybdenum is re-oxidised to the Mo(V) (red) stage, which is fairly stable in air, and complete oxidation is effected by the permanganate, but the net result is the same, viz. Mo(III)- Mo(VI) vanadium is re-oxidised to the V(IV), condition, which is stable in air, and the final oxidation is completed by slow titration with potassium permanganate solution or with cerium(IV) sulphate solution. 

Prepare a standard ammonium chloride solution as follows. Dissolve 3.141 g ammonium chloride, dried at 100 °C, in ammonia-free water and dilute to 1 L with the same water. This stock solution is too concentrated for most purposes. A standard solution is made by diluting lOmL of this solution to 1 L with ammonia-free water 1 mL contains 0.01 mg of NH3. 

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 of iron(III). Use method (a), (b) or (c). (a) Dissolve 0.7022g ammonium iron(II) sulphate in 100mL water, add 5mL of 1 5 sulphuric acid, and run in cautiously a dilute solution of potassium permanganate (2 g L 1) until a slight pink coloration remains after stirring well. Dilute to 1 L and mix thoroughly. lmL = 0.1mg of Fe. (6) Dissolve 0.864 g ammonium iron(III) sulphate in water, add 10 mL concentrated hydrochloric acid and dilute... 

Prepare the standard nickel solution by dissolving 0.673 g pure ammonium nickel sulphate in water and diluting to 1 L 1 mL contains 0.1 mg of Ni. The solution may be further diluted to a basis of 0.01 mg of Ni per mL, if necessary. Pure nickel may also be employed for the preparation of the standard solution. 

Construct a calibration curve using standard ammonium chloride solution (1-100 mg L-1 Cl-) and deduce the chloride ion concentration of the test solution with its aid. 

Procedure. Into lOOmL graduated flasks, each containing lOmL of the ammonium acetate solution, 1 mL of the dilute sulphuric acid, and 3 mL of the eriochrome blue black RC solution, run in from a burette 15.0, 20.0, 25.0, 30.0, 35.0, 40.0, 45.0, and 50.0 mL of the standard aluminium solution. Dilute each of the above solutions with distilled water, and adjust to a pH of 4.6 0.2 if necessary before making up to the 100 mL mark. Allow the solutions to stand for at least 1 hour. 

Trace amounts of molybdenum were concentrated from acidified seawater on a strongly basic anion exchange resin (Bio-Rad AG1 X-8 in the chloride form) by treating the water with sodium azide. Molybdenum (VI) complexes with azide were stripped from the resin by elution with ammonium chlo-ride/ammonium hydroxide solution (2 M/2 M). Relative standard deviations of better than 8% at levels of 10 xg per litre were attained for seawater using graphite furnace atomic absorption spectrometry. 

Stein et al. [673] have described a simplified, sensitive, and rapid method for determining low concentrations of cadmium, lead, and chromium in estuarine waters. To minimise matrix interferences, nitric acid and ammonium nitrate are added for cadmium and lead only nitric acid is added for chromium. Then 10,20, or 50 pi of the sample or standard (the amount depending on the sensitivity required) is injected into a heated graphite atomiser, and specific atomic absorbance is measured. Analyte concentrations are calculated from calibration curves for standard solutions in demineralised water for chromium, or an artificial seawater medium for lead and cadmium. 

Soliman and Belal investigated argentimetric (67,68) and mercurimetric (69) methods. Hydralazine precipitates silver from ammoniacal silver nitrate solution. The silver is dissolved with hot nitric acid and titrated with ammonium thiocyanate solution. Alternatively, mercury is precipitated from alkaline potassium mercuric iodide solution. The precipitated mercury is dissolved by adding excess standard iodine solution. The excess iodine is back-titrated with sodium thiosulfate solution after acidifying with acetic acid. 

In a typical extraction, 50 jiL of plasma was treated with 25 /./I. of internal standard solution and then diluted with 200 /iL of 3% ammonium hydroxide. The C18 /./-SPE tips were conditioned with 150 /iL of methanol and then 300 /./I. of 3% ammonium hydroxide. The sample was exhaustively extracted by aspirating and dispensing the plasma samples seven times from the dilution tube. For the wash, 90 /./I. of 3% ammonium hydroxide followed by 100 /./I. of methanokwater (20 80 v/v) was used. Elution was achieved with 50 /./I. of methanokwater (90 10 v/v). After evaporation of the collected eluate in the 96-well block, the residues were reconstituted in 200 fjL of mobile phase A B... 

The effect of ammonium nitrate concentration on the peak height of a 60ng Atrazine standard solution is shown in Fig. 9.8, the optimum response being at a concentration of approximately 4pg pL-1. 

Procedure Pipette 25 ml of a standard 0.1 N AgN03 solution into a glass-stoppered flask (iodine-flask), dilute with 50 ml of DW, add to it 2 ml of nitric acid and 2 ml of ferric ammonium sulphate solution and titrate with ammonium solution to the first appearance of red-brown colour. Each ml of 0.1 N silver nitrate is equivalent to 0.007612 g of NH4SCN. 

Fig. 3.157. Pherogram of standard solution by CE-UV/DAD. Conditions sample injection, 20 mm x 30 s capillary, 62 cm X 75 pm i.d. untreated fused silica (50 cm to the detector) running solution 50 mM ammonium carbonate buffer (pH = 9.5) CE voltage, 20 kV detection wavelength, 240 nm temperature, 30°C. Peaks I, Orange II II, p-phenolsulphonate III, o-phtalate IV, p-sulphobenzoate (100 mg/1 of each). Reprinted with permission from S. Takeda et al. [196].

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