MT 110 - Mercurial impurities in technical and formulated mercurials

 

Content Handbook F

 

Outline of method

110.1 General TLC method for samples containing more than 1% of inorganic mercury

The sample is dissolved in acetone/aqueous sodium chloride or dioxane/aqueous sodium chloride. The solution is spotted on to a silica gel TLC plate, developed with carbon tetrachloride/acetone, and sprayed with copper(II) sulphate and potassium iodide/sodium sulphite solutions. The resulting spots are compared with standard spots from pure mercury(II) chloride to give the inorganic mercury content of the sample.

110.2 Gravimetric method

Inorganic and any organic mercury compounds soluble in acetic acid are extracted from the sample by stirring it with hot acetic acid. The mixture is filtered, the filtrate is neutralized with ammonia, and potassium iodide is added to precipitate phenylmercury(II) compound as phenylmercury(II) iodide which is filtered off. The filtrate is heated with bis(ethylenediamine) copper(II) sulphate solution to form an insoluble mercury complex [bis(ethylenediamine)mercury(II) sulphate] which is then filtered off, and weighed.

110.3 Sulphide colorimetric method

110.3.1 Ethylmercury(II) chloride and phenylmercury(II) chloride -Determination of inorganic mercury salts.

The sample is dissolved in acetone and the solution is saturated with hydrogen sulphide. The colour of the solution is compared with standards prepared in a similar manner from mercury(II) chloride.

110.3.2 Mercury(II) iodide - Determination of water-soluble mercury(II)compounds

The sample is shaken with water, filtered and the filtrate is treated with hydrogen sulphide. The colour of the solution is compared with standards prepared in a similar manner from mercury(II) chloride.

110.3.3 Mercury(II) oxide technical - Determination of other mercury salts

The sample is shaken with dilute ethanol, filtered and the filtrate is treated with hydrogen sulphide. The colour of the solution is compared with standards prepared in a similar manner from mercury(II) chloride.

110.3.4 Mercury(I) oxide technical - Determination of mercury(II) chloride

The mercury(II) chloride is extracted with diethyl ether, the ether is evaporated off and the residue dissolved in water. The solution is treated with hydrogen sulphide. The colour of the solution is compared with standards prepared in a similar manner from mercury(II) chloride.

110.3.5 Phenylmercury(II) dimethyldithiocarbamate - Determination of inorganic mercury(II) salts.

The sample is shaken with acetone, filtered, and the filtrate is treated with hydrogen sulphide. The colour of the solution is compared with standards prepared in a similar manner from mercury(II) chloride.

110.4 2-Ethoxyethylmercury(II) and 2-methoxyethyl(II) chlorides

The sample is dissolved in sodium hydrogencarbonate solution, any insoluble material is filtered off and its mercury content determined by oxidation with sulphuric acid and potassium nitrate.

110.5 Mercurial seed treatments containing mercury(II) chloride and/or iodide - Determination of free mercury and mercury from mercury(I) salts

The sample is extracted with hot methanol and filtered. Any soluble material is refluxed with zinc and acetic acid. The resultant zinc amalgam is dissolved in nitric acid and the mercury content is determined by titration with standard thiocyanate solution.

110.6 Phenyl mercury(II) chloride - Determination of water-soluble inorganic and/or organic mercury compounds

The material is shaken with water, filtered and the filtrate is treated with hydrogen sulphide.
If the solution blackens, then water-soluble mercury(II) salts are present. Reject the sample. If any white precipitate is produced, filter off, digest in the normal manner and determine the content of soluble organic mercury.

 

Scope

110.1 General TLC method for samples containing more than 1% of inorganic mercury

The method is suitable for the determination of 1 to 14% inorganic mercury salts in technical and formulated organomercury(II) compounds.

110.2 Gravimetric method

The method is suitable for the determination of inorganic mercury, in phenylmercury(II) acetate, chloride and nitrate.