Charpentier-Volhard s method

These theoretical considerations correspond to the last stage of Charpentier-Volhard s method with X = SCN . 

Argentometry in Addic Medium Charpentier-Volhard s Method... 

Following Charpentier-Volhard s method (1874), a nitric acid solution and a known quantity in excess of silver nitrate solution are added to the medium under study. Silver ions in excess are determined by titration with a standard solution of an alkaline... 

Fig. 37.1 Error made in the determination of chloride ions by Charpentier-Volhard s method when the silver chloride precipitate is not removed before the addition of thiocyanate ions...

In a first stage, it must undergo the action of a hot concentrated sodium hydroxide solution to be mineralized. After acidification of the solution by nitric acid, it is titrated according to Charpentier-Volhard s method. 

At first, they are heated in alkaline medium. The chlorine ions liberated from thiamphenicol are directly titrated by a standard silver nixate solution after acidification of the medium by nixic acid. The final point is detected by potentiomeXy. The indicator electrode is a silver electrode. In the cyclophosphamid case, the titration is carried out according to Charpentier-Volhard s method. For chlorambucil, the mineralization of chlorine atoms is performed in refluxing propylene glycol containing potassium hydroxide. 

Numerous determinations of the same kind as those given here have been recommended in previous pharmacopeias. Generally, they consist of titrating halide ions, once they are formed by mineralization, by an argentometric method. Usually, it is Charpentier-Volhard s method. We can also cite the examples of lindane (y-benzenehexachloride, DTT, iodoform, eosine, chlorotrianisene, etc.). The preliminary mineralization is carried out in alkaline medium, that is, with sodium or... 

Most of these titrations are recommended according to Charpentier-Volhard s method. In this context, its great advantage lies in the fact that during the titration, the medium remains acidic. In these conditions, the quaternary ammoniums to be titrated, which were formed by the protonation of amines and which are usually hydrochlorides orhydrobromides, do not precipitate because they remain protonated. The reaction that occurs is... 

The titration is a back titration according to Charpentier-Volhard s method after filtration of silver sulfide as well as acidification of fhe solution. Theophylline gives a silver theophillinate precipifafe only fofally in ammonia and after healing. Silver theophillinate does nol form in diluled acid medium, and ils precipilalion is incomplete in pure water. 

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