Friday, 29 August 2014

Gold purification on the sidewalks of Bangkok

Gold purification on the sidewalks of Bangkok

(Solution to Quiz: What are these people doing? from a week ago.)

"Making gold" would sound more spectacular, but apart from some arcane nuclear conversions, you can't make gold.

I spotted these people near Saran Rom (in fact I was looking for boys, but this was far more interesting, so I spent the rest of the night observing, taking pictures and chatting).

What they are doing is a kind of gold parting, not to be confused with cupellation. They collect gold scrap and filings from jeweler and convert it to pure gold. While gold alloys with high gold content (as used in jewelry and dentistry) are insoluble in nitric acid, gold alloys with low gold content are soluble, leaving pure gold behind. They melt the impure gold with lead (?) and then dissolve the lead (?) and other metals with acid.

The brown bottles (look like beer bottles) contain nitric acid. I saw him opening the plastic lid with his teeth and then spitting out to get rid of traces of nitric acid in his mouth. The empty bottles were discarded by throwing in the canal (this way they don't break, they float or sink):

The ultimate proof that it's nitric acid: brown nitrogen dioxide fumes, toxic, make sure the wind comes from behind:

Gold remains as fine powder, neither yellow nor shining, and is melted with flux to a nugget (about 30 g, I saw it on the scale and hold it in my hand, but forgot to take a picture). A bellows is used to drive air through petrol (?) for the burner, flux is added with bare fingers:

All these operations took place on the sidewalk, in semi-darkness, illuminated by the headlights of a car or flashlight, sitting, standing or crouching. A nearby spot with a lamppost was better lit, but already occupied. Notice complete absence of protective equipment (lab coat, safety goggles, gloves). If I were to perform these operations, it would look something like this (plus gloves, picture of me during my PhD):

Copyright 2014 ChristianPFC


  1. everyone knows what you look like, why still so scared of showing your face.

  2. I think the scrap gold is dissolved in mercury, and they used the torch(oxythylene) to evaporate the mercury, leaving behind the gold nuggets. It's a dangerous technique as mercury is toxic.

  3. is this beside the canal where the boys stand, beside the park itself-where there are also some bus-shelters (sala's)?
    If you go again, can you ask where they moved that evening/nightmarket to-for the 20 bt poh-DVDs?

  4. How do you know what I look like?

    There is no mercury involved. Mercury or Cyanide are used to extract gold from rocks, but not for purification.

    It's opposite the west gate of Saranrom. I will inquire about market next time I am in the area.

  5. You use the same name on everything, kind of gives it away.
    Planet romeo, Grinda All the websites, not so hard.


Comments are currently unmoderated and open to everyone. I will see how this works out and might switch to moderation. Please sign your comment with a name or identifier.