The use of complex-forming reagents in the polarographic analysis of inorganic substances XIV. Polarographic behaviour of ethylenedisulphurdiacetic acid in the presence of a mercury salt

✍ Scribed by Desanka Sunjević; Jan Doleal; Miloslav Kopanica

• Publisher: Elsevier Science
• Year: 1969
• Weight: 337 KB
• Volume: 20
• Category: Article
• ISSN: 0022-0728
• DOI: 10.1016/s0022-0728(69)80129-4

✦ Synopsis

Ethylenedisulphurdiacetic acid (I) was first prepared by RAMBER6 AND TIBERG 1 HOOC-H2C-S-CH2-CH~-S-CH.oCOOH (I) but so far little attention has been given to its chelate-forming abilities; literature data are sparse and only of a qualitative nature. Recent studies based on potentiometric and spectrophotoinetric measurements have shown that this reagent forms i : i metal: ligand chelates with some divalent metals ~-4.

In the present paper the polarographic behaviour of mercuric ions in the presence of ethylenedisulphurdiacetic acid (H2Z) is described with a view to finding the molar ratio of the chelate-forming substance and determining the stability constant of the resulting chelate by means of polarographic data.

EXPERIMENTAL

Apparatus

Polarograms were recorded with a Metrohm Polarecord E-26I and with an H-type polarog~aphic cell with a large separate saturated mercury sulphate electrode. An electrode of large (4.5 cm ~) active surface was prepared to prevent its polarization. pH-values were measured with a Radiometer pH-ineter PHM 4 using a glass electrode as reference electrode. For conductivity Ineasurements, a Radiometer conductivitymeter CDN[-2 was used in connection with an ultrathermostat.

Reagents

Ethylenedisulphurdiacetic acid was prepared by PODI_AHA 4. Other solutions used were prepared from reagent-grade chemicals.

Buffer solutions (Britton-Robinson; acetic acid-sodium acetate; borate-* No.