Metaborate - 4 mol and 8 mol

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Jorge Omar - 02 Oct 2003 13:46 GMT

From the Rio Tinto site:

*Exists as sodium metaborate 8 mol below 53.6?C;
transition to sodium metaborate 4 mol, which is stable, from
53.6?C to 105?C.

http://www.borax.com/pdfs/dist/Profile_Sodium_Metaborate_4_Mol.pdf

This is from the 4 mol metaborate; the same is written in the 8 mol page.

Jorge

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Richard Knoppow - 04 Oct 2003 07:54 GMT

> From the Rio Tinto site:
>
> *Exists as sodium metaborate 8 mol below 53.6?C;
> transition to sodium metaborate 4 mol, which is stable, from
> 53.6?C to 105?C.

http://www.borax.com/pdfs/dist/Profile_Sodium_Metaborate_4_Mol.pdf

> This is from the 4 mol metaborate; the same is written in the 8 mol page.
>
> Jorge

For more on what Kodalk is see Ryuji Suzuki's site at:
http://silvergrain.org/Photo-Tech/chemistry-misnomers.html

He points out that Kodalk is described in old literature
as Sodium Metaborate Octahydrate, but is actually the
Tetrahydrate.
An accurate formula for making Sodium Metaborate in
solution is:

1.0 gram Sodium Tetraborate = 0.692 gram Borax + 0.145 gram
Sodium Hydroxide.

While this isn't Octahydrate it can be used in place of
Kodalk in all the old Kodak and other formulas calling for
Kodalk Balanced Alkali or Sodium Metaborate.

Signature

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com

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Dan Quinn - 04 Oct 2003 11:01 GMT

"Richard Knoppow" <dickburk@ix.netcom.com> wrote

> 1.0 gram sodium tetraborate = 0.692 gram borax + 0.145 gram
> sodium hydroxide.

Is that 1.0gr sodium metaborate octahydrate = 0.692gr sodium
tetraborate decahydrate + 0.145gr sodium hydroxide?
Is that in conflict with the equivalence cited by Mr. Erlick
very recently in a previous post this subject?
If they are not equivalent then one or perhaps both of the
two cited are in error.

From Mr. Erlick's post: 1gr metaborate = .4545 borax + .0953
sodium hydroxide.

I think this matter should be cleared up. I suspect that the
use of Kodalk and the metaborate may have at it's foundation
another rational.
As I've stated ALL the borates revert to the ortho form in
solution. The ortho form has the greatest buffering potential.
The meta with it's single hydrogen affinity has no real buffering
capacity at all! Dan

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Jorge Omar - 04 Oct 2003 13:42 GMT

Ive posted recently this link for an article by Michael Gudzinovicz re
mixing metaborate tetra vs octa. Here it's again:

http://www.pofig.net/photodb/viewChemicals.do?action=Details&id=19

Jorge

> "Richard Knoppow" <dickburk@ix.netcom.com> wrote
>
[quoted text clipped - 18 lines]
> The meta with it's single hydrogen affinity has no real buffering
> capacity at all! Dan

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Dan Quinn - 07 Oct 2003 10:53 GMT

> Ive posted recently this link for an article by Michael Gudzinovicz re
> mixing metaborate tetra vs octa. Here it's again:
>
> http://www.pofig.net/photodb/viewChemicals.do?action=Details&id=19

That is Dr.M. Gudzinowicz's third revision of the formula.
How about this one from Maxim M. Muir: To make 1 liter, 165gr borax,
and 35gr sodium hydroxide. That is for 1 liter 20% metaborate.
Compare with the below formulas. Dan

> > "Richard Knoppow" <dickburk@ix.netcom.com> wrote
> >
[quoted text clipped - 18 lines]
> > The meta with it's single hydrogen affinity has no real buffering
> > capacity at all! Dan

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Jorge Omar - 07 Oct 2003 12:56 GMT

Is it that one?

http://www.rit.edu/~andpph/pf-faq/faq-43.html

Look for FAQ 43.11

That's the one that, on a cold day gave me very nice looking metaborate
crystals!
At first the borax wouldn't solve completelly (hydroxide humidity?) so I
kept on adding a bit at a time until it solved.

Of course, the solution became useless after crystalization.

Jorge

dan.c.quinn@att.net (Dan Quinn) wrote in news:b379902d.0310070153.4e2f482
@posting.google.com:

>> Ive posted recently this link for an article by Michael Gudzinovicz re
>> mixing metaborate tetra vs octa. Here it's again:
[quoted text clipped - 5 lines]
> and 35gr sodium hydroxide. That is for 1 liter 20% metaborate.
> Compare with the below formulas. Dan

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Dan Quinn - 07 Oct 2003 23:09 GMT

> Is it that one?
> http://www.rit.edu/~andpph/pf-faq/faq-43.html Look for FAQ 43.11
[quoted text clipped - 14 lines]
> > and 35gr sodium hydroxide. That is for 1 liter 20% metaborate.
> > Compare with the below formulas. Dan

A correction need be made: AFAIK that link points to Dr. M. G's
third version, and is the second revision. An exact formula for the
meta from
the tetra plus NaOH is proveing to be a challenge.
I and Ryuji Suzuki agree that a sound approach to ph control is to
blend a bicarbonate with a carbonate. I use an all neutral to alkaline
chemistry and intend to do more work with those two.
Dan

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Jorge Omar - 08 Oct 2003 02:13 GMT

Just my thoughs on this matter:

See (to clarify the idea), the PDF file:

http://www.borax.com/pdfs/dist/Profile_Borax_Decahydrate.pdf

There is a tritation curve with HCl where pH is fairly constant (buffer
effect) and then suddenly start to fall quickly (buffer capacity
exausted).

I think that when one adds hydroxide, the behavior is alike, but ofcorse
to a higher pH.

If the desired pH is close to the inflection (and this seems to be the
case), the hydroxide dosage becomes very critical.
And if one adds that solid hydroxide is very much hygroscopic and it's
weight/pH changes due to water absorption...

Jorge

>> Is it that one?
>> http://www.rit.edu/~andpph/pf-faq/faq-43.html Look for FAQ 43.11
[quoted text clipped - 25 lines]
> chemistry and intend to do more work with those two.
> Dan

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Dan Quinn - 08 Oct 2003 10:22 GMT

> Is it that one?
> http://www.rit.edu/~andpph/pf-faq/faq-43.html
> Look for FAQ 43.11

Yes that's the one.

> That's the one that, on a cold day gave me very nice looking metaborate
> crystals!
> At first the borax wouldn't solve completelly (hydroxide humidity?) so I
> kept on adding a bit at a time until it solved.
> Of course, the solution became useless after crystalization.

I've had that happen with a 6% borax solution. Borax is not all
that soluable. I think that if there is sodium in excess some borate
may precipitate in the ortho form. Boric acid, that is orthoboric
acid, may be the least soluble acid of boron and it's borate perhaps
the least soluble of the borates.
I've not yet got the whole picture in mind where it concerns
boron and it's acids and salts. Dan

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Dan Quinn - 30 Oct 2003 11:51 GMT

> "Richard Knoppow" <dickburk@ix.netcom.com> wrote
>
> > 1.0 gram sodium tetraborate = 0.692 gram borax + 0.145 gram
> > sodium hydroxide.

The above equivalence agrees with my determination. For 100
grams of metaborate tetrahydrate use 69 grams of borax and 14.5
grams of lye.
With the lye first in solution first additions of borax will
produce the orthoborate. Further additions of borax will convert
the ortho to the meta. A surplus of borax, the tetra, will result
in a mix of the meta and the tetra.

> As I've stated ALL the borates revert to the ortho form in
> solution.

For the acids of boron H2O, H OH is needed. For the sodium
borates Na OH is needed. For the rubidium borates, rubidium
hydroxide is needed.

> The ortho form has the greatest buffering potential.
> The meta with it's single hydrogen affinity has no real buffering
> capacity at all! Dan

The ortho with it's triprotic charater likely does have greater
buffering capacity than the monoprotic meta. But the meta does
have REAL buffering capacity. It will take on or yield up a
hydrogen as the concentration of H+ in solution increases
or decreases. Dan

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Jorge Omar - 30 Oct 2003 13:06 GMT

This beeing the case, the mixing order would not matter.
What one shoud avoid are:
- Lack of borax (not usually the case, but can happen): there will be orto
in solution and pH will be higher due to excess hydroxide; it may lead to
precipitate crystalization sometime after the solution is mixed.
- Excess borax: pH will be lower due to beeing a mix of tetra and meta.
This is the usual situation when hydroxide is not pure and one simply mix
by weight.
If the solution is not highly concentrated, the tetra will be completelly
solved and there won't be any visual clues since there will be no
precipitate.

Jorge

> With the lye first in solution first additions of borax will
> produce the orthoborate. Further additions of borax will convert
> the ortho to the meta. A surplus of borax, the tetra, will result
> in a mix of the meta and the tetra.

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