Precipitation techniques silver nitrate

Silver nitrate-carrier precipitations can be used advantageously to collect microgram to milligram quantities of azide ion by coprecipitation, using 10 mg chloride ion as a carrier in dilute acid solutions. Although no data have been reported using the technique, it cannot be excluded on a theoretical basis. 

The population balance technique was also successfully applied to the run-seed, triple-jet precipitation of silver halide crystals (Wey 1990). In addition to silver nitrate and halide salt solutions, a third solution containing stable silver halide seed crystals was simultaneously introduced into the precipitation vessel. For a seed-crystal solution that contains monodisperse seed... 

The first analysis is for the chloride ion which serves to balance the charge of the complex ion. Many complex ions are stable enough that ligand chlorides attached directly to the central metal ion (inside the bracket in the formula) are not precipitated as silver chloride, AgCl, upon the addition of silver nitrate, AgN03, solution, whereas anionic chlorides (outside the bracket in the formula) are precipitated quantitatively by this technique. For example, only one Cl precipitates from the following complex. 

As silver nitrate solution is added to the sodium chloride, silver chloride precipitates. As long as CT ions are in excess, they adsorb on the precipitate particles. At the end point, no CT ions are left in solution and negative fluorescein ions are then adsorbed, giving a pink colour to the precipitate. The technique is sometimes known as Fajans method. 

The AgCl precipitate formed after the addition of silver nitrate reagent can be detected with nephelometric or turbidimetric techniques. In this way the chloride concentration can be measured in water samples using appropriate calibration curve [36-38]. To be able to measure in the low concentration range, the measurements are carried out in water-organic solvent mixtures such as water-methanol [39]. 

Place about Ig of the sample into a 150 cm flat-bottomed stoppered flask and add 100 cm of acetone. Swirl to dissolve, then add dropwise, with swirling 1 cm of a 50 per cent solution of silver nitrate, in distilled water. Shake the flask well and allow it to stand until the precipitate has settled out. Filter the precipitate through a Whatman No. 541 filter paper, wash it with a small amount of distilled water, then with acetone and finally with a small amount of diethyl ether. Retain the filtrate and washings (filtrate A, Figure 7.7). Dry the precipitate (precipitate B) in a desiccator and determine its infrared spectrum of using the nujol emulsion technique. 

Evaporate to dryness and examine only an aliquot of the ether extract. To the rest, prior to evaporation, add a few drops of 50 per cent silver nitrate solution, dropwise, with shaking. Shake well and allow the precipitate to settle, then filter through a Whataian No. 541 filter paper washing well with ether. Dry in a desiccator and examine by infrared spectrophotometry and the nujol emulsion technique. Also, suspend an aliquot of the precipitate in chloroform, acidify with a little hydrochloric acid, shake and carry out nuclear magnetic resonance spectroscopic examination of the chloroform extract. This should suffice for the identification of the thioacid. The dark colour of the silver complex is probably due to the presence of silver sulphide. 

For back-titration the method of Volhard is used and is probably the most widely employed technique for determination of halide ions. The halide is precipitated from a nitric acid solution by addition of excess silver nitrate and the excess is back-titrated with ammonium thiocyanate using ferric alum as indicator at the end-point the blood-red ferric thiocyanate is formed. Since silver thiocyanate is much less soluble than silver chloride, ammonium thiocyanate will attack the silver chloride precipitate and so cause erroneous results. For this reason the silver chloride must be removed or protected before titration of the excess silver nitrate is begun. This is best obtained by filtering off the precipitate before back-titration, but this step is time-consuming. As an alternative, some organic solvent may be added which will form a protective coating around the silver chloride and for this purpose nitrobenzene appears to be the most satisfactory. It should be remembered, however, that nitrobenzene is a powerful... 

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