[alt-photo] Re: HYDROSCOPIC!

[Ryuji Suzuki]

Dear Bob,

I bet ammonium thiocyanate is there as a ligand for gold, and
for this purpose, thiocyanate in this formula is in excess. If
I were to make a small bet (well, that's less than $10 worth
of gold, I guess :-), the amount of ammonium thiocyanate is
not critical.

Also, ammonium thiocyanate is not used as an alkaline agent in
this formula. I don't think pH would be a good assay for
it. If anything, I think specific gravity would be more
useful. If you can measure specific gravity of, say, 25%
solution, and adjust your stock to match that value, I think
it'd be close enough for your purpose.

Ryuji

--
Ryuji Suzuki
"The essence of the beautiful is unity in variety." (Felix Mendelssohn)

From: "BOB KISS" <bobkiss at caribsurf.com>
Subject: [alt-photo] HYDROSCOPIC!
Date: Mon, 10 May 2010 11:50:18 -0400

> DEAR LIST,
> 
>             Can anyone help me with the following?
> 
>        I want to mix some Ammonium Thiocyanate gold toner.  Bloody Ammonium
> Thiocyanate is seriously hydroscopic.  The sealed plastic env in the B&S
> toner kit is liquid!  No problem here because it is premeasured to make a
> small amount of toner.  However, the local university which is happy to get
> rid of their supply has two 500g  bottles of Ammonium Thiocyanate that are
> both liquid!!!  No one can say for sure if any has been taken from the jars
> so no way to be certain of the concentration.  
> 
>             I see no reason I can't use these liquid Am Thio solns from the
> bottles but I need to know when I have added enough per liter for the toner.
> I am betting that all these alkaline salts (Borax, Amm Thio, etc.) are
> mainly to set the pH for the gold toner which determines the resulting
> particle size and hence color.  Might it be possible to determine the
> correct pH in the liter of the alkaline soln and simply add the soln from
> the bottle to, let's say, 800 ml of distilled water until it reaches that
> pH?  Adjust vol & more Amm Thio to 1 liter at the correct pH?  
> 
>             Of course, the trick question is, what IS the correct pH?
> 
>  
> 
>             The formula from Chris James' book is:
> 
>  
> 
>                         800 ml dist water
> 
>                             25g  Ammonium Thiocyanate
> 
>                               2g  Tartaric Acid
> 
>                               5g  Sodium Chloride
> 
>                           20ml 1% gold chloride soln
> 
>  
> 
>             Any ideas?
> 
>                         CHEERS!
> 
>                                     BOB
> 
>  
> 
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