# Kodalk from borax plus sodium hydroxide ...

Discussion in 'Darkroom Developing and Printing' started by lloyd, Oct 1, 2003.

1. ### lloydGuest

oct103 from Lloyd Erlick,

Recently the following formula for producing sodium metaborate
(Kodalk) appeared in this ng. I don't understand how a hundred grams
of sodium metaborate comes from about fifty five grams of reagents.
Does the water in which all this takes place enter and make up the
weight? Perhaps someone could correct the numbers ...

100g sodium metaborate (Kodalk) == 45.45g borax + 9.53g NaOH

regards,
--le

lloyd, Oct 1, 2003

2. ### Gregory W. BlankGuest

Think liquid solution;

When I first got into making my own Metaborate I had email conversations
with Maxim Muir who gave me some help. According to my proceedure
Metaborate is mixed at a ratio of 1) part Sodium Hydroxide + 5) Parts Borax.
Maxim went on to indicate that Kodalk is closer to an Octo-Hydrated version that
appears the darkroom Cookbook, However the 1to5 version works fine for me.

I use 25 grams of Sodium Hydroxide +
125 grams Borax
+ 800 ml of water and stir
+ additional water to make a liter.

Gregory W. Blank, Oct 1, 2003

3. ### Jorge OmarGuest

I believe this formula to be fairly right, but see:

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

I'm having trouble with this mix since NaOH absorbs a lot of water and
CO2 from the air and results are not repetitive, so pH changes from one
lot to the next.
I'm considering using a NaOH liquid solution to see if I get more
constant results.

Jorge

wrote in 4ax.com:

Jorge Omar, Oct 1, 2003
4. ### Patrick GainerGuest

I use the CRC Handbook definition of sodium metaborate which includes 4
molecules of water. Borax has 10. NaOH has none. The water it absorbs
from air is not part of the crystal. If you leave a bit of NaOH out,
after while you will have a puddle of NaOH in solution.

When you calculate the solution percent, don't forget that when you
dissolve the metaborate, a large part of its weight is water of
crystallization.

Patrick Gainer, Oct 1, 2003
5. ### Dennis O'ConnorGuest

Dissolve your NaOH in distilled water and keep adding the lye until no more
will dissolve and the solution is saturated with a few crystals in the
bottom of the jug... At that point you have saturated solution... A
measured amount of the saturated solution should always result in the same
Denny

Dennis O'Connor, Oct 1, 2003
6. ### Jorge OmarGuest

Thanks, Dennis

Do you know the saturation percentage for NaOH?

Jorge

Jorge Omar, Oct 1, 2003
7. ### Dennis O'ConnorGuest

Oh gaaawwd.... It's been nearly 50 years since inorganic chemistry, and I
don't have a Chemistry Handbook here at the office to look up the
solubility... But, from the hazy memory of a voice murmuring across a
sleepy classroom over a half century ago that a saturated solution of lye
requires equal weights of lye and water...

So, a saturated NaOH solution can be prepared by mixing equal weights of
NaOH pellets and distilled water. The saturated lye should stand for several
days to allow the carbonates to precipitate. Only the clear upper solution
should be decanted leaving the precipitates/carbonates in the bottom... If
the pellets are fairly wet, meaning they contain considerable water already,
you may want to reduce the weight of the distilled H2O by 10% <or some such>
so that you are sure of it being a saturated solution... If there is a
powdering of lye still undissolved in the bottom after 2 or 3 days, it is
saturated...
If I misremember a saturated solution of NaOH as being equal in weight to
the water it is dissolved in, someone may correct me..
Cheers ... Denny

Dennis O'Connor, Oct 1, 2003
8. ### Jorge OmarGuest

Thanks again, Dennis

Not very easy, but doable...

Jorge

Jorge Omar, Oct 1, 2003
9. ### Richard KnoppowGuest

There was a rather extensive discussion of the hydration
of Kodalk in the Pure-Silver list recently. While Kodak has
always refered to Kodalk as the octahydrate it seems likely
that it is actually the tetrahydrate. In any case,
tetrahydrate can be used for Kodalk with equal results in
all the old formulas.

Richard Knoppow, Oct 1, 2003
10. ### Patrick GainerGuest

I once bought 25 lbs of Kodalk. I'm pretty sure it said it contained the
tetrahydrate, but that was about 30 years ago. Like all the other
things, the label only said "contains" and not "consists of". I don't
know for sure what the equilibrium form might be for the crystals, but I
suspect the tetrahydrate. That and the anhydrous are the only ones
listed in the CRC Handbook unless you count the perborate, which
contains one peroxide and 3 waters.

get through your spam filter to mail you directly. How come you got
through mine?

Regards,
Pat Gainer

Patrick Gainer, Oct 2, 2003
11. ### friendGuest

pretty close. solubility of sodium hydroxide monohydrate is 109.2 g in
100 g of water at 20°C, 126 g at 40°C, 178 g at 60°C, and sodium
hydroxide (anhydrous)313.7 g at 80°C.
at 20°C total content of saturated NaOH is 52.2%.

friend, Oct 2, 2003
12. ### friendGuest

just fuse one part of borax with one part of sodium carbonate.
commercial metaborate has variable hydration.
when you mix hydroxide with borax it is safer to have an excess of
borax, rather than excess of hydroxide.
one mole of borax reacts with two moles of sodium hydroxide giving
four moles of metaborate.

friend, Oct 2, 2003
13. ### Jorge OmarGuest

And at what temperature will this fusion take happen?

Thanks,

Jorge

Jorge Omar, Oct 2, 2003
14. ### Dan QuinnGuest

RE: wrote
I'm quite sure that formula is Dr. M. J. Gudzinowicz creation. I've
wondered about that equality for some time.
The borates derive form the corresponding acids of boron. There
are ortho, meta, and tetra boric acids and borates. The acids are
H3BO3 (ortho), which on warming yields HBO2 (meta), and that on
warming yields H2B4O7 (tetra). The borates become progresively
dehydrated.
In water at usuall temperatures, they all revert to the ortho
form. That is both the tetra and meta convert to the ortho form.
So what goes? It must be kept in mind that the borate form
itself changes. Hydration in this case goes beyond, mono,
penta, etc, H2O hanging on at the end of some borate.
Solubility may be what goes. At room tempeature the meta is at
least five times more soluble.
The doctor has said that 100gr NaBO2 = 45.45gr Na2B4O7 + 9.53gr
NaOH. I'll convert all the borates on each side of the equation
to ortho and then we will know. Dan

Dan Quinn, Oct 3, 2003
15. ### friendGuest

around 700-800°C, easy with Bunsen burner or an oven.
Borax melts around 740.

friend, Oct 3, 2003
16. ### Jorge OmarGuest

I've seens lots of postings on how to mix metaborate, tried them and I
would say that without first making a saturated NaOH solution it is
nearly impossible to make a correct solution.

A question for the chemists over there:

If one adds excess NaOH, metaborate crystals will precipitate (both as
powder like and real crystaline structures).

Would decanting the liquid and drying the crystals be Ok or, as I think,
the crystals will have a lot of NaOH contamination (at least in the
surface) in it?

Thanks,

Jorge

(Dan Quinn) wrote in

Jorge Omar, Oct 3, 2003
17. ### Jorge OmarGuest

I'm afraid I couldn't do it in my kitchen...

Jorge

Jorge Omar, Oct 3, 2003
18. ### Gregory W. BlankGuest

The formula I gave you I know will work however if getting all
the chemistry into solution is your goal, try mixing half strength
that is: same amount of chemistry + plus twice the water then use twice
as much solution in the end....works like a charm.

Gregory W. Blank, Oct 3, 2003
19. ### Gregory W. BlankGuest

Provided that the ratios are correct if your mixing the solution in
water between 100F and 120F it should go into solution, but does
require some stirring.

Gregory W. Blank, Oct 3, 2003
20. ### Jorge OmarGuest

Gregory

I know the formula works - I've mixed it a few times.
The problem I'm having is that, according to the Rio Tinto site, a 1%
metaborate solution will have a pH of 11 and 11.44 for a 5%.
I always measure less than that (the NaOH absorbs water and its weight
increases); then I have to add (slowly) more NaOH until the pH is right
(tritation like).
If one overdo the NaOH, it will cystalize as soon as temperature goes
down, and pH will rise to over 12.
Add to that my not very stable pH meter (Hanna Checker) and it becomes a
PIA...

I just whish I could find a source for small quantities over here
(Brazil).

Jorge

Jorge Omar, Oct 3, 2003