Silver nitrate , titrations

Assay of hydrogen cyanide can be done by specific gravity or silver nitrate titration. Sulfur dioxide in hydrogen cyanide can be deterrnined by infrared analysis or by reaction of excess standard iodine solution and titration, using standard sodium thiosulfate or by measurement of total acidity by... 

Marquis and Lebel [534] precipitated potassium from seawater or marine sediment pore water using sodium tetraphenylborate, after first removing halogen ions with silver nitrate. Excess tetraphenylborate was then determined by silver nitrate titration using a silver electrode for endpoint detection. The content of potassium in the sample was obtained from the difference between the amount of tetraphenyl boron measured and the amount initially added. 

The end points of precipitation titrations can be variously detected. An indicator exhibiting a pronounced colour change with the first excess of the titrant may be used. The Mohr method, involving the formation of red silver chromate with the appearance of an excess of silver ions, is an important example of this procedure, whilst the Volhard method, which uses the ferric thiocyanate colour as an indication of the presence of excess thiocyanate ions, is another. A series of indicators known as adsorption indicators have also been utilized. These consist of organic dyes such as fluorescein which are used in silver nitrate titrations. When the equivalence point is passed the excess silver ions are adsorbed on the precipitate to give a positively charged surface which attracts and adsorbs fluoresceinate ions. This adsorption is accompanied by the appearance of a red colour on the precipitate surface. Finally, the electroanalytical methods described in Chapter 6 may be used to scan the solution for metal ions. Table 5.12 includes some examples of substances determined by silver titrations and Table 5.13 some miscellaneous precipitation methods. Other examples have already been mentioned under complexometric titrations. 

Ammonium thiocyanate-silver nitrate titrations (Volhard s Method). 

AMMONIUM THIOCYANATE-SILVER NITRATE TITRATIONS (VOLHARD S METHOD)... 

International Standard Organization. 1989. Water quality. Determination of chloride. Silver nitrate titration with chromate indicator (Mohr s method). ISO 9297. International Organization for Standardization, Case Postale 56, CH-1211, Geneva 20 Switzerland. 

The total concentration of salts in a solution was determined by analyzing the concentration of chloride ion by the usual silver nitrate titration. Chlorides were present in all systems studied, and the mole fraction of the chloride was determined at the time the solution was prepared (see above). 

Stability of the compound in the formulation (i.e., free base versus the salt). The chloride content can be determined using ion chromatography and/or silver nitrate titration. 

For measurements on mixed salts, tetraethylammonium chloride solution was required. It was prepared by grinding the quaternary base iodide with an excess of silver chloride and some water, filtering, diluting and standardizing by silver nitrate titration. The design of the potentiometer circuit was derived from Penick, o whose method of adjustment was also used. This circuit was very sensitive to changes of external electric fields, and the thermostat, which contained the cell, had to be stirred by water circulated by a rotary pump, placed at some distance from the thermostat. 

In practice this determination is carried out by adding to a weighed quantity of the chloropicrin in a small flask fitted with a condenser, an excess of an aqueous-alcoholic solution of sodium sulphite, prepared by dissolving 10 gm. sodium sulphite in 250 ml. water and diluting with an equal volume of ethyl alcohol. The liquid in the flask is then carefully heated so as to distil off all but about 10 ml. This is then diluted with water to 100 ml. and 10 ml. of nitric acid and an excess of a standardised solution of silver nitrate are added. The solution is then warmed to drive off the nitrous gases and to coagulate the silver chloride, and then cooled and the excess silver nitrate titrated with a solution of ammonium thiocyanate (ferric alum indicator). 

Argentometric titration method has been applied to the determination of sulfonamide mixtures. The sulfonamides are quantitatively precipitated by the addition of excess standard silver nitrate solution, the precipitated silver salts removed by filtration, and the excess silver nitrate titrated with standard ammonium thiocyanate using ferric alum as indicator (32). 

BIOLOGICAL PROPERTIES Koc 1-70 for most soluble forms at pH less than 9.2, most free cyanide is expected to convert to HCN highly volatile and biodegradable when released to water have the potential to leach into groundwater do not adsorb to soil nitriles have the highest mobility in soil can be detected in water by silver nitrate titration or colorimetric analysis using pyridine pyrazolone... 

Chloride may be determined by the Volhard method. The sample is acidified with concentrated nitric acid and silver nitrate is added, which reacts with the chloride, and then the mixture is boiled. After cooling, the pale yellow solution is diluted and the excess silver nitrate titrated with potassium thiocyanate solution using ammonium ferric sulfate as indicator. The ash may also be used for this determination. 

Since the major ions are present in seawater at constant ratios to one another, it is normally not necessary to measure the concentrations of all the ions since the concentration of one will allow the prediction of the others. Thus, chloride has traditionally been measured using a silver nitrate titration, and from this the salinity (i.e., total dissolved salt concentrations) can be derived. Now, however, conductivity is the routinely measured parameter and this is converted to salinity by a relationship agreed internationally with interlaboratory agreement ensured by the distribution of standard seawater samples for instrumental calibration. The use of modern inductively coupled conductivity measurements with careful temperature controls allows salinities to be determined with accuracy and precisions of the order of +0.01% or better. 

These three phases were gently stirred without mixing at 25 i 1 °C using a magnetic stirrer. At specified time intervals, the concentrations of metal picrate in both aqueous phases were determined by UV spectroscopy. It was confirmed by the silver nitrate titration method using 5% potassium chromate as indicator that no chloride ion was transported from, aqueous phase I to aqueous phase II. 

If a chloride solution is acidic, calcium carbonate powder is added to neutralize the acid. One use of silver nitrate titrations is to determine the formulas of chlorides. 

Tj = sodium nitrate titration (ml) obtained in sample combustion T, = silver nitrate titrations (ml) obtained in blank combustion N = normality of silver nitrate. 

Mittenberger and Gross " determined chlorine in PVC by fusion with sodium peroxide followed by silver nitrate titration of the chloride produced. Tanaka and Morikawa described a semimicro technique for the determination of total chlorine in PVC using a semimicro method based on the Schoniger oxygen flask and Fajans method. 

Tb = silver nitrate titrations (mis) obtained in blank combustion. 

The conditions must be strictly adhered to and low laboratory temperatures must be avoided also the reaction mixture must not be heated, otherwise the excess of alkali decomposes the chloroform formed and high results are obtained. This was confirmed by Harrington, Boyd and Cherry who showed that some hydrolysis of the chloroform occurred at room temperature in the excess of alkali present. If, after neutralisation of the excess alkali, the chloride formed is titrated with OTN silver nitrate using potassium chromate as indicator, a correction for this hydrolysis is possible. Since 3 mols. of sodium chloride produced are equivalent to 4 mols. of sodium hydroxide required for the chloroform hydrolysis, 2/15 of the silver nitrate titration must be deducted from the N sodium hydroxide absorbed in the original hydrolysis. 

The official methods of determining pharmaceutical salts of halogen acids are by the Volhard silver nitrate titration for chlorides and bromides and the Lang iodate method for iodides. The equivalents are given in Table 19 ... 

Despite recent developments in salinity measurement based on electrical conductivity, density, or the refined measiurement of refractivity, a silver nitrate titration still remains the internationally acceptable referee procedure and it is also still the most convenient method to use when a high precision is required in a laboratory having only limited and sporadic requirements for salinity analyses. 

Free amine and amino acid. An aliquot of the original sample is titrated with perchloric acid in acetic acid solvent, with addition of mercuric acetate. This titration determines the sum of free amine, free amino acid, and chloride concentrations (140). Chloride is easily determined separately by ion chromatography or by silver nitrate titration. 

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