Borax clarification

Radost · Nov 3, 2023

I have been using Decahydrate “Borax” - Borax Pentahydrate for my chems.
Just run out and got 20 mules Borax from walmart but when I read the label it says sodium Tetraborate.
Kodak formulas say Borax Decahydrate,
Can somebody help me out with this?
Would both work for D96 developer?
My uneducated research turned out this:
Borax Decahydrate is the refined form of natural sodium borate.
One is 5 the other is 4 if my ancient greek is good enough.

john_s · Nov 3, 2023

According to posts I've read over the years, Kodak, for example, refer to the decahydrate as "borax" for published formulas. (Deca means 10). Borax at the shops is the decahydrate.

koraks · Nov 3, 2023

Radost said:
One is 5 the other is 4 if my ancient greek is good enough.

Our Greek may be at similar levels (mine is pretty atrocious!) and yes, penta = 5 and tetra = 4.

However, let's not confuse the tetraborate with pentahydrate and decahydrate.

All borax is tetraborate, with the formula Na2B4O7. Note the 4 borons, hence the name 'tetraborate'.
However, as sold, this salt comes in three forms:
1: As a pure salt without any water, i.e. anhydrous.
2: As a salt with nominally five atoms of water per sodium tetraborate molecule: the pentahydrate or Na2B4O7.5(H2O) (which technically is apparently a trihydrate, but it's commonly referred to as the pentahydrate).
3: As a salt with nominally ten atoms of water per sodium tetraborate molecule: the decahydrate or Na2B4O7.10(H2O) (which confusingly is really a octahydrate...)

They're all 'borax', but the molecular weights differ somewhat due to the different amounts of water you get mixed in with the sodium tetraborate.
The decahydrate has a molecular weight of 381.37 g/mol.
The pentahydrate has a molecular weight of 291.35 g/mol.
The anhydrous form AFAIK is not commonly sold as a grocery item; its molecular weight is 201.22 g/mol.
This means the decahydrate is roughly 25% heavier than the pentahydrate, so you'll need to use around 25% more of it if the recipe calls for the pentahydrate. That's an approximation, but it will be close enough for photochemistry.

Alan Johnson · Nov 3, 2023

I believe 20 mule team borax is this, CAS 1303 96 4, MW 381.37:

https://www.borax.com/BoraxCorp/media/Borax-Main/Resources/Specifications-Sheets/borax-decahydrate-technical-granular.pdf?ext=.pdf

Radost · Nov 3, 2023

Thanks,
Great info.

So considering the d96 liter only calls for 4.5 grams I can use the pretty mich the same amount?
But honestly I will just buy the correct chemical because I am ocd.

koraks · Nov 3, 2023

Yes, if Kodak calls for the decahydrate, and you're using 20-Mule Team, you're actually using the stuff Kodak prescribes. Use whatever amount they list in the formula.

snusmumriken · Nov 3, 2023

koraks said:
Our Greek may be at similar levels (mine is pretty atrocious!) and yes, penta = 5 and tetra = 4.

However, let's not confuse the tetraborate with pentahydrate and decahydrate.

All borax is tetraborate, with the formula Na2B4O7. Note the 4 borons, hence the name 'tetraborate'.
However, as sold, this salt comes in three forms:
1: As a pure salt without any water, i.e. anhydrous.
2: As a salt with nominally five atoms of water per sodium tetraborate molecule: the pentahydrate or Na2B4O7.5(H2O) (which technically is apparently a trihydrate, but it's commonly referred to as the pentahydrate).
3: As a salt with nominally ten atoms of water per sodium tetraborate molecule: the decahydrate or Na2B4O7.10(H2O) (which confusingly is really a octahydrate...)

They're all 'borax', but the molecular weights differ somewhat due to the different amounts of water you get mixed in with the sodium tetraborate.
The decahydrate has a molecular weight of 381.37 g/mol.
The pentahydrate has a molecular weight of 291.35 g/mol.
The anhydrous form AFAIK is not commonly sold as a grocery item; its molecular weight is 201.22 g/mol.
This means the decahydrate is roughly 25% heavier than the pentahydrate, so you'll need to use around 25% more of it if the recipe calls for the pentahydrate. That's an approximation, but it will be close enough for photochemistry.

That’s such a helpful answer, it should be a sticky.

Radost · Nov 3, 2023

koraks said:
Yes, if Kodak calls for the decahydrate, and you're using 20-Mule Team, you're actually using the stuff Kodak prescribes. Use whatever amount they list in the formula.

Thank you so much.
Where do you see the Kodak formula that calls for decahydrate?

koraks · Nov 3, 2023

I didn't. I took that from your post.

Radost · Nov 3, 2023

This is the only thing it says

koraks · Nov 3, 2023

Well, that's pretty definitive alright.

Radost · Nov 3, 2023

koraks said:
Well, that's pretty definitive alright.

Thank You for clarifying. I stopped studying chemistry in 5th grade.
My understanding is pretty basic.

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