Letter 21596

What is Liver of Sulphur? [South Africa] 

+++

I am a Maker of Pewter figurines I read in a jewellery book that you can oxidize (blacken) pewter with Liver of Sulphur. No one in South Africa seems to know what this chemical is. Can you please tell me another name for it or what it is made of. I have been blackening my pewter with Nitric Acid in the past but it gives a finish that is too dark (ie hard to polish the black off sufficiently) and sometimes inconsistent.

Thank you,

Andrew Postus
private - Durban, KZN, South Africa

Sourcing (what's this?):

Sulphurated Potash.

Neil Bell
Red Sky Plating - Albuquerque, NM, USA

See question 20448 - all will be revealed.

Trevor Crichton R&D practical scientist - UK

Liver of sulphur is not a chemical compound but is a mixture, prepared as a brown mass by fusing sulphur and potassium carbonate.(P. J. Durant 1954, General and Inorganic Chemistry page 491)

6S + 3K₂CO₃ = 2K₂S₂ + K₂S₂O₃ + 3CO₂

When I last prepared this I melted sulphur and slowly added a measured quantity of potassium carbonate as per the above formulae.

The mixture was stirred until bubbling ceased and was then allowed to cool. It was then broken up and bottled. The mixture was stable.

A dilute solution can be used to tarnish copper and other metals.

Note that hydrogen sulphides are also evolved which smell bad in low concentration but are poisonous in higher concentrations. Thus a fume cupboard is mandatory.

Claudio Ferrero
- Sydney, NSW, Australia

Answer or follow-up on this subject (in non-commercial fashion).

 

Post a new question or inquiry on a different subject.