Re: Highly concentrated gold colloid

From: Gizmo (dmat_at_coco.com)
Date: 08/30/04 

Date: Mon, 30 Aug 2004 04:40:06 GMT

Dave wrote:

> Does anyone know a method of making highly concentrated aqueous gold colloid?
>
> D

Define concentrated. At really high concentrates, the untreated colloid is very
unstable.

1 gram of chlorauric acid dissolved in 500ml water of highest purity.
5 ml of this solution is diluted to 100 ml and neutralised with 0.1 N potassium
carbonate and heated. The gold in this diluted solution is then reduced by adding
a few drops of formaldehyde or hydrogen peroxide. This gives you a nucleation
solution with gold particles in the range of 10-30 Angstroms.
Next take your remaining original chloroauric solution and neutralise with
potasium carbonate solution and added the same reducing agent you used before.
Wait 20 seonds then add your nucleating solution which provides nuclei for gold
to deposit on. Typically this gives particles in the range of 80-90 Angstroms.
This solution can also be used as a nucleating solution to make even larger
particles.

Noet that this is all under ideal conditions. Water purity as well as the purity
of all other reagents can greatly affect the outcome.

You aren't planning to drink the colloidal solution are you?

Gizmo.

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