Author Topic: Colloidal Gold Color  (Read 714 times)

Offline xozhang3

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Colloidal Gold Color
« on: February 15, 2021, 04:49:47 PM »
Hi,

I used to make colloidal gold with gold chloride from saltlakemetals.com.  Now I bought some siriusmetals.com gold chloride. The colloidal gold made from the new gold chloride seems much darker than that with saltlakemetals gold chloride.  Another thing drew my attention was that when I put new gold chloride into DW, DW appears much more yellow.  Of course I used the same amount of DW and gold chloride containing the same amount of Au.  Finally I also noticed that I have to more drops of sodium carbonate to reduce the siriusmetals gold chloride.

Has anyone experienced the same? And what would you think is happening here?

Thanks.

Offline SaltyCornflakes

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Re: Colloidal Gold Color
« Reply #1 on: February 15, 2021, 07:04:51 PM »
More yellow in gold chloride & more color in CG means that you got higher PPM, I would say. As long as it is not discolored into the purple spectrum, you should be good.

If the % concentration of the gold chloride from both sellers is advertised as the same, either saltlakemetals is giving you less or siriusmetals is giving you more than advertised.

Offline xozhang3

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Re: Colloidal Gold Color
« Reply #2 on: February 16, 2021, 03:40:55 AM »
Makes sense.

Thank you very much!

Offline xozhang3

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Re: Colloidal Gold Color
« Reply #3 on: February 16, 2021, 03:54:59 AM »
I bought the 5% 100 ml gold chloride solution from Siriusmetals.  So I use 4 ml where I should use 20 ml of 1% of 100 ml solution for 500 ml of CG.

On another note, I was able to make perfect CG with Saltlakemetals gold chloride premixing Karo, sodium carbonate, and gold chloride and then heating in microwave.  But with SiriusMetal GC, this way of making CG ends up with turbidity.  I have to heat DW with Karo first to boil and then add gold chloride, and mix the solution while dripping sodium carbonate and stirring the solution with a plastic spoon at the same time, as suggested by Kephra, doing so using Siriusmetals GC produces much darker but clear CG.
« Last Edit: February 16, 2021, 04:02:57 AM by xozhang3 »

Offline SaltyCornflakes

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Re: Colloidal Gold Color
« Reply #4 on: February 16, 2021, 03:29:29 PM »
There's also the possibility that a lower ml volume is harder to gauge accurately and easier to overshoot than a higher one.

Offline kephra

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Re: Colloidal Gold Color
« Reply #5 on: February 16, 2021, 05:02:29 PM »
Quote
doing so using Siriusmetals GC produces much darker but clear CG.
Which can also mean larger particle sizes.

Another possibility concerning technique is that there is a pH difference between the two kinds of gold chloride.
Colloidal Silver is only a bargain if you make it yourself.

Offline xozhang3

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Re: Colloidal Gold Color
« Reply #6 on: February 16, 2021, 07:02:22 PM »
There's also the possibility that a lower ml volume is harder to gauge accurately and easier to overshoot than a higher one.

That's definitely possible.  Too bad I don't have saltlakemetals gold chloride any more to do a more careful compare.

Offline xozhang3

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Re: Colloidal Gold Color
« Reply #7 on: February 16, 2021, 07:24:18 PM »
Quote
doing so using Siriusmetals GC produces much darker but clear CG.
Which can also mean larger particle sizes.

Another possibility concerning technique is that there is a pH difference between the two kinds of gold chloride.

As I add sodium carbonate drops, the solution is at first light purple, then light ruby red.  Since I do not know the exact number of drops of SC to use, I keep adding more drops ( to a total of 28 or so drops for 500ML of CG) until it gets dark ruby red.

I read somewhere in the forum that Karo is used to reduce gold chloride.  So sodium carbonate is used to change the pH.  Would more sodium carbonate increase the particle size?

Offline xozhang3

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Re: Colloidal Gold Color
« Reply #8 on: February 16, 2021, 09:39:18 PM »
I just made another 500 ML CG with SM gold chloride.  I paid more attention this time to counting the drops of sodium carbonate.

I mentioned 28 drops previously but actually I had to use 42 drops this time.  I think I had 28 drops as an idea in my mind but I did not count the numbers.

I had to keep adding drops because the solution stays light purple/pink. Once the number of drops reached 40 or 41, it turned quickly ruby red of the same darkness as before.  It seems I cannot reduce the amount of sodium carbonate.


Offline kephra

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Re: Colloidal Gold Color
« Reply #9 on: February 17, 2021, 08:38:05 PM »
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It seems I cannot reduce the amount of sodium carbonate.
Which lends credence to your gold chloride being more acidic than salt lake metals product.
The pH must be above 7 for the reduction to work properly.  pH 8.5 is ideal.

Colloidal Silver is only a bargain if you make it yourself.

Offline xozhang3

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Re: Colloidal Gold Color
« Reply #10 on: February 18, 2021, 03:11:30 PM »
Quote
It seems I cannot reduce the amount of sodium carbonate.
Which lends credence to your gold chloride being more acidic than salt lake metals product.
The pH must be above 7 for the reduction to work properly.  pH 8.5 is ideal.

Thank you Kephra for the explanation!  It makes me feel much comfortable knowing what is going on when making CG.

Offline xozhang3

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Re: Colloidal Gold Color
« Reply #11 on: February 24, 2021, 02:44:24 AM »
I experimented a bit more.  This time I put Karo, sodium carbonate in DW, stir and then heat in microwave. After the solution gets boiling, I put in gold chloride (from siriusmetals), it immediately turns purple, I keep stirring, and when I feel enough stirring does not make it turn ruby red, I add more drops of sodium carbonate and stir until it turns ruby red. 

The result appears good ruby red but not as deep as heating DW and Karo to boil first and then adding GC and SC.

I also notice that the white plastic spoon I use to stir is tainted with light purple and the purple is hard to wash off and I have to throw it away.  I can't help noticing that the CG made this way has some purple hue. I don't know if my mind is playing some trick on me or not.