FMF - Friends of Minerals Forum, discussion and message board

[Rei]

So at long last I got a bottle of super iron out for mineral cleaning. I put a bunch of samples in a 3% solution - calcite, some with chalcedony, zeolites, etc, plus a matrix (basalt or similar). I was a bit concerned when from all samples except the calcite I saw streams of tiny bubbles forming (and I must stress tiny, I'm not used to seeing bubbles that small, it was kind of weird - one sample formed a column of bubbles from underneath that was so fine I thought it was a hair and tried to pluck it out). Anyway, very concerned that I might be destroying my samples, I removed the non-calcite samples.

I must ask, is this normal, for super iron out to have some reaction that causes bubbling? Or was that indeed something being destroyed? I just want to get rid of surface oxides.

[Pete Richards]

I can't speak specifically to the bubbles - they could be reaction products or they could just be trapped air oozing out of a thin crack. The general rule is to try whatever you use on a sample you can afford to lose before you use it for real.

Waller solution is buffered, so at least until the buffer gets used up, the pH should remain stable. I'm not sure the same is true of Super Iron Out, though I think the other chemicals are similar.

There is a danger that either of these can attack calcite, fluorite, and other minerals if iron oxides are not present, or even if they are. I have ruined fluorite specimens using the Waller solution (as I recall - or was it Super Iron Out?).

So, again, test and observe before you use them on "real" specimens. And test for longer than you think the "real" application will require. And rinse well!

Good luck!

[Rei]

I did choose some of my least impressive specimens. No, it was definitely not air oozing out, I'm 100% about that. So you're saying that a bubbling reaction is not normal with iron out?

[alfredo]

SIO is slightly acidic. Won't hurt most minerals, but I wouldn't use it on calcite - at least not for more than a minute or two.

[Rei]

Funny, calcite is the only one that's *not* bubbling ;)

Besides, what other cleaning solution could one use on calcite?

[Dale Hallmark]

Maybe....a little baking soda...maybe ;-)

Dale

[GneissWare]

The pH of SIO is 5.5 to 6. You can buffer it up to near pH 7 by adding a small amount of baking soda (Sodium bicarbonate). This will not significantly affect the active ingredients of SIO, sodium hydrosulfite and sodium metabisulfite.

The fine bubbling is normal. You can get more info in Rock's article at https://www.mindat.org/article.php/403/Cleaning+Quartz

[Rei]

Rock's article didn't mention the bubbling but good to know that it's okay! :) I'll put my test specimens back in.

[GneissWare]

John Betts has an article on cleaning with Waller solution (essentially SIO). He rightly describes the reaction as "the solution works by reducing Fe+3 to Fe+2 and then dissolving Fe+2 in the Citric Acid." This reduction reaction causes the bubbling by release of O2, if I remember correctly.

[Jordi Fabre]

Just in case you didn't see it: How to remove iron stains?

[lluis]

Hi, All

If a chemist serves for something
-The hydrosulphite in Waller's solution, when oxidized releases sulphuric acid, and for that there is an extra sodium bicarbonate: to neutralize free sulphuric acid
-Hydrosulphite never releases O2. So, I fear that the bubbling is CO2 being released...

In wikipedia
https://en.wikipedia.org/wiki/Sodium_dithionite
And this article is right.

Also, can anyone tell me what is SIO? If pH is acidic (very few, but acidic), it cannot be Waller's, that is slightly basic (over 7)

With best wishes

Lluís

[Rei]

[Rei]

[lluis]

Hi, Rei

Sorry to be the sorcerer... Chemists are used to be seen as the bad ones.... :-)

The mixture of sodium metabisulfite and sodium hydrosulfite has a small trouble. Sodium metabisulfite is acidic, and to place a product that is acid sensitive, like sodium dithionite (aka sodium hydrosulphite), well, is a nice way to get big troubles. A fire somehow great (great is for *GREAT*) happened one time in Switzerland because some packages of sodium hydrosulphite got wet and at the end, ignited. Firemen were not informed and they shot more water, and flames got bigger.... Not nice.

Sodium hydrosulphite decays to sodium bisulphite only in presence of water (with sodium thiosulphate) or if in presence of water and oxygen, to sodium bisulphite and sdoium bisulfate. In both cases, with a release of heat that increases the rate of decomposition.

If you say that they have the buffering agents (sodium carbonate), then the sodium bisulfate means that the sodium sulphite used to produce the sodium hydrosulphate is not completely exhausted...
2 NaHSO3 + Zn → Na2S2O4 + Zn(OH)2
bisulphate hydrosulphate

The CO2 released, as you say, would come first from sodium carbonate. For that, calcite would not be damaged: it is the reason why Waller's solution has been created: to clean iron from acid sensitive items, as calcite....

And no, when you reduce Fe3+ to Fe2+ you do not liberate oxygen, you only give an electron to Fe3+ to produce Fe2+
Fe3+ + e- -> Fe2+

Hydrosulphite gives the electrons, oxidizing it to sulphate....

Sorry for long rant.... :-(

With best wishes

Lluís

[Rei]