# How to make TetraEDTA in 39% solution



## emi (Dec 18, 2018)

I've already learned from reading other posts that I can not use EDTA Disodium in place of Tetradisodium EDTA. I'm going to order Tetrasodium EDTA and return the Disodium EDTA. But I noticed it comes in dry form. The recipe I'm using calls for "Tetra EDTA in 39% solution". I just wanted to make sure here. I combine 39% of the water weight to make this correct? So if I have 100g of distilled water, I should dissolve 39g EDTA into it, correct? (NOT 39% EDTA 61% water)

This is the recipe I'm doing. IrishLass's Creamy Shea/Cocoa Liquid Soap. I'm done with the paste stage and going to put it in the fridge until my EDTA and meadowfoam oil arrives! https://www.soapmakingforum.com/threads/my-creamy-cocoa-shea-gls-tutorial.57974/


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## DeeAnna (Dec 18, 2018)

Dissolve 39 grams of EDTA in 61 grams of distilled water to make 100 grams of 39% EDTA solution. 

Concentration % = EDTA wt / (EDTA wt + water wt) X 100 = 39 / (39 + 61) X 100 = 39 / 100 X 100 = 39%

***

If you dissolved 39 grams of EDTA in 100 grams of water, your solution concentration would be --

Concentration % = EDTA wt / (EDTA wt + water wt) X 100 = 39 / (39 + 100) X 100 = 39 / 139 X 100 = 28%


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## Misschief (Dec 18, 2018)

Thank you for this, DeeAnna. My EDTA arrived last week but I haven't used it yet.


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## DeeAnna (Dec 18, 2018)

You can also make a 50% EDTA solution if you prefer. Makes the math easier in the long run. I wrote about this awhile back: https://www.soapmakingforum.com/threads/yes-virginia-you-can-make-a-50-edta-solution.62761/


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## Misschief (Dec 18, 2018)

Dang... just realized today that I ordered Disodium EDTA instead of Tetrasodium EDTA.


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## shunt2011 (Dec 18, 2018)

I did the same thing by accident on my last order.


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## DeeAnna (Dec 18, 2018)

Disodium EDTA can be converted into Tetrasodium EDTA by reacting the Di with NaOH or other strong alkali. I strongly suspect it's as simple as measuring the correct amount of powdered Di and adding it to your lye solution. Di won't dissolve in plain water like Tetra will, but it should dissolve in lye solution and react with the NaOH to form Tetra.

I haven't done the calculations, so I don't have solid numbers at the moment about how much Di to use and how much NaOH it will consume as it converts to Tetra. Here's a link to what appears to be some reputable although not very detailed advice -- https://chemistscorner.com/cosmetic...-to-formulate-tetrasodium-edta-and-etidronate

I can do the math and get some numbers for you, but I'd need someone to test the practical use of Di for me, since I don't have any on hand. (Or someone to send me a small sample.) In particular, I'd want to know how well it dissolves in NaOH solution. Does it clump up on the top and is fiddly to get stirred into the lye? Does it need to be stirred a lot to dissolve once it is mixed into the lye liquid? Does it take a lot of time? Is there any great amount of heating from the reaction? Or is it dump in and swirl a bit and easy-peasy you're done?

edit:
Okay, I worked through the math. It looks like you want to use essentially the same weight of Di as you would Tetra. For example, if I normally use 5 g Tetra per 1000 g oil, I'd do the same for Di -- add 5 g Di per 1000 g oil.

The (very small) catch to using  Di is every 5 grams of Di will consume about 1 g NaOH. We use so little EDTA in soap that you might not feel the need to adjust for this -- it's such a tiny error. If you're a geek like me, however, you Want To Know These Things so you can decide. 

So for those folks who have Disodium EDTA in their soaping pantries, now's the time to put your mad scientist hat on and try it. Please tell me if there are any tips or tricks to using Di. Remember -- it won't happily dissolve in plain water, but from what I can tell, it will dissolve in the strong alkali solutions we normally use to make soap. Would someone give it a try and report back?

I'll add this information to the EDTA article I have on my Soapy Stuff section. That way others can benefit from this insight.


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## Misschief (Dec 18, 2018)

You, my dear DeeAnna, are amazing. Has anyone ever told you that? I won't be able to try anything yet but will certainly try to make soap next week (I'm off the entire week).


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## DeeAnna (Dec 18, 2018)

Thank you, @Misschief!

I'm hoping maybe SaltedFig, GalaxyMLP, or someone else with a chemistry and math background will doublecheck my thinking. I think I've got the numbers straight, but it never hurts to get a second opinion.


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## emi (Dec 18, 2018)

DeeAnna said:


> You can also make a 50% EDTA solution if you prefer. Makes the math easier in the long run. I wrote about this awhile back: https://www.soapmakingforum.com/threads/yes-virginia-you-can-make-a-50-edta-solution.62761/



Thank you DeeAnna for answering my question! I'm so glad I asked. I thought it was like bread hydration where the EDTA was 39% of the water. I've never dealt with EDTA and from what I've read so far, it sounds like a great thing to put into all soaps. I have really hard water here in LA so it will definitely be useful. Maybe I'll start putting it in all my soaps? Like how I've started to become with sodium lactate. I just put it in all my batches now. Is there any reason or situation where I wouldn't want to use TetraEDTA? or sodium lactate?

Your chemistry knowledge is so impressive and inspiring!  The Disodium EDTA and Tetrasodium EDTA that I ordered will be arriving in the next couple days. I ordered the Di by mistake and ordered the Tetra the next day which was yesterday when I posted this thread question. Instead of returning it, maybe I'll hold on to the Disodium to do some experimenting with and give you some of the results you're asking for! 

Also, I read the link you provided about EDTA 50% solution and I'm still not sure why I would want to use 50% instead of some other number like 39%. Is it just to have less water involved, or are there recipes out there that ask for tiny dry weight (like milligrams) of EDTA where a 50% solution would be easier to calculate? 

Thank you so much for such a quick reply to my question plus all this great info! I can't say enough how grateful I am for this forum!


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## DeeAnna (Dec 19, 2018)

_"...I thought it was like bread hydration where the EDTA was 39% of the water...."_

You have a valid point, but your technical training encourages you to see the situation from a different perspective than most people. Non-chemistry folks almost always base the amount or percentage of an ingredient on the _total weight_ of the solution or mixture.

I'd say that's generally true here on SMF, although it never hurts to ask and make sure, as you wisely did. In soaping, we often see the "ppo" convention used, which is basing ingredients on the weight of fats, not on the total weight. So even in non-chemistry groups, there can be exceptions to this rule.*

There's only water and EDTA in this solution, so you'd use the calculation I gave previously to calculate % EDTA on the basis of _total solution weight_ --

% EDTA in the solution = (wt EDTA) / (wt EDTA + wt Water) X 100 = 39 / (39+61) X 100 = 39%​
The other way to calculate concentration is to base the amount or percentage of an ingredient _on the main liquid_ (more correctly called the "solvent") in the solution or mixture. That would be the basis you were thinking of. It's not an everyday basis to use, but using a solvent basis is handy when making up a given solution or mixture -- there's less math to fiddle with.

For the EDTA solution, water is the solvent, so this is the calculation you'd use to calculate the % EDTA on a _solvent basis_ --

% EDTA based on solvent weight = (wt EDTA) / (wt Water) X 100 = 39 / 61 X 100 = 64%​_***

"...I'm still not sure why I would want to use 50% instead of some other number like 39%...."_

I'd say the main reasons why people use a 50% solution rather than some other percentage are convenience and accuracy. This is the same reason one would use a solvent basis rather than a total solution basis -- the numbers are easier to calculate, so the math is easier and there's less chance for error.

Another reason is to increase the overall consistency of the soaping process. Many of us masterbatch NaOH as a 50% solution, so why not use a 50% concentration for EDTA and other solutions or mixtures? This common basis reduces the chance for mistakes in making these solutions and in using them.

Last -- probably least important for an EDTA solution -- is that a 50% solution requires a smaller container than a 39% solution.

***

* There's another exception to the rule that I see in soaping circles. That's when people talk about making brine (solseife?) soap. You will see people get into arguments about how much table salt you can dissolve in plain water to make a saturated solution. Some say the answer is about 26% salt and others say it's about 35% salt.

They're actually both right except neither side is presenting the numbers correctly. The correct way to state this info is this way -- At room temperature, a brine of table salt and water is saturated at about 26% salt by weight on a _total solution basis_ or 35% by weight on a _water (solvent) basis_.

I think this confusion comes when non-chemist people look for information about making a saturated salt brine and don't understand that chemistry info can be presented in a number of different ways. They just see a number -- 26% or 35% -- and don't realize there's more to the story.


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## shunt2011 (Dec 19, 2018)

@DeeAnna   Thank you so very much for all that!  Unfortunately I'm not likely to be making any soap till after the new year.   When I relocate my EDTA I can send some to you if you want to test it yourself.


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## SaltedFig (Dec 19, 2018)

DeeAnna said:


> Disodium EDTA can be converted into Tetrasodium EDTA by reacting the Di with NaOH or other strong alkali. I strongly suspect it's as simple as measuring the correct amount of powdered Di and adding it to your lye solution. Di won't dissolve in plain water like Tetra will, but it should dissolve in lye solution and react with the NaOH to form Tetra.
> 
> I haven't done the calculations, so I don't have solid numbers at the moment about how much Di to use and how much NaOH it will consume as it converts to Tetra. Here's a link to what appears to be some reputable although not very detailed advice -- https://chemistscorner.com/cosmetic...-to-formulate-tetrasodium-edta-and-etidronate
> 
> ...





DeeAnna said:


> Thank you, @Misschief!
> 
> I'm hoping maybe SaltedFig, GalaxyMLP, or someone else with a chemistry and math background will doublecheck my thinking. I think I've got the numbers straight, but it never hurts to get a second opinion.



EDTA's aren't my thing, so up until now I didn't know that much about it (other than it's use in medical circles, prior to hearing about it in soaping) and I certainly didn't know it's function in plant growth (which has piqued my interest - I'm going to have a bit of a closer look at that ).

The thing that I didn't know, in the products you all use, is whether you are using the hydrate or anhydrous product, but I kind of concluded that it didn't actually matter (so long as the calculations were kept consistant), so I chose the hydrate version.

Anyway, I checked your numbers, and they look about right - I got 0.215, or 21.5%, as the multiplier, which is roughly equivalent to your 5 grams of H2Y2 to 1 gram of NaOH, to convert to Y4 and some spare water.

I did find a manufacturing document that looks similar to your idea of adding disodium EDTA to the lye solution. The manufacturer added the NaOH solution to the EDTA solution to convert the disodium EDTA to tetrasodium EDTA - it states that the product (Ethylenediaminetetraacetic acid disodium salt dihydrate) is slowly soluble at room temperature up to 0.26M (stated as making a final solution of approx. 96mg in 1 ml) and the solubility increases as the pH increases.

In other bits of research, I found that there's graphs on the pH needed for each conversion step (these should be fairly easy to find - let me know if you need a link), but the bottom line is that the pH of the solution needs to reach over 10.3 for the tetrasodium EDTA to form ... under that and most of the conversion will not have taken place.

Summary:
Yes, 5 parts disodium EDTA to 1 part NaOH is a good way to remember it.
Add the sodium hydroxide slowly to the disodium EDTA solution
Make sure the final pH reaches at least 10.3 to convert to tetrasodium EDTA (higher is ok).


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## DeeAnna (Dec 19, 2018)

_"...the bottom line is that the pH of the solution needs to reach over 10.3 for the tetrasodium EDTA to form ... under that and most of the conversion will not have taken place...."_

I agree. That's why I'm thinking our usual lye solutions (25% or more NaOH) should work fine for this, although one doesn't need remotely that much NaOH to get the pH sufficiently high. The pH of NaOH solution is just under 12 for a 0.1% NaOH solution and just over 13 for a 1% solution.

_"...Add the sodium hydroxide slowly to the disodium EDTA solution..."_

Chemists typically prepare EDTA solutions by adding disodium or "no sodium" EDTA to a weak NaOH solution, not just water. So why dissolve the disodium EDTA in water first? Couldn't we modify the chemists' method by adding disodium EDTA powder directly to the NaOH solution a person is going to use to make soap?

Or am I totally missing an important point, @SaltedFig? I hope you'll help me out by clarifying.


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## SaltedFig (Dec 19, 2018)

DeeAnna said:


> _"...the bottom line is that the pH of the solution needs to reach over 10.3 for the tetrasodium EDTA to form ... under that and most of the conversion will not have taken place...."_
> 
> I agree. That's why I'm thinking our usual lye solutions (25% or more NaOH) should work fine for this, although one doesn't need remotely that much NaOH to get the pH sufficiently high. The pH of NaOH solution is just under 12 for a 0.1% NaOH solution and just over 13 for a 1% solution.
> 
> ...



The document I referred to was for the preparation of a standardized medical solution, so I expect that there is an exact method, with pages and pages of standards, checks and normal corporate/industrial production protocols. 

Bottom line - Yes, I think that this can be done the way around you are suggesting (in fact, I think it will be easier, as long as the EDTA is converted from disodium EDTA to tetrasodium EDTA within a reasonable amount of time)

From what I've read, the EDTA solution also stores quite well, so it could be also be designed as a lye/EDTA pre-mix (which would also be useful if the conversion takes a while) 

(The only spanner in the works I can see with this approach is if the excess NaOH is an issue)


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## DeeAnna (Dec 19, 2018)

_"...it will be easier, as long as the EDTA is converted from disodium EDTA to tetrasodium EDTA within a reasonable amount of time..."_

I get the impression that it dissolves fairly quickly with sufficiently high pH. That said, I haven't read anything about dissolving EDTA in the high concentrations of NaOH like we use. They're adding only a small bit of NaOH to raise the pH just high enough to dissolve the EDTA and no more.

I guess our guinea pigs will have to let us know whether we're full of bull manure or not.  Wish I had some disodium to try it myself because I'm very curious about this.


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## SaltedFig (Dec 19, 2018)

Testing time! 

DeeAnna, perhaps you could create a thread to call for testers?


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## Misschief (Dec 19, 2018)

DeeAnna said:


> Wish I had some disodium to try it myself because I'm very curious about this.



I'd be happy to send you some but I'm not sure how good an idea it would be to send a white powder across the border.


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## cmzaha (Dec 19, 2018)

I have used Disodium Edta in soap by adding my 12 grams to my lye solution. It worked fine. Usually I use Disodium EDTA in my lotion recipe


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## DeeAnna (Dec 20, 2018)

Thank you, Carolyn! One data point from @cmzaha. Do you remember if it was at all difficult to dissolve the disodium EDTA?

I agree with sending white powder over the border, @Misschief. Thanks for the offer, but I think both of us will be happier if you don't. 

I've got to run (DH needs oral surgery). I'll get a call-to-action thread started later today or tomorrow.


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## emi (Dec 21, 2018)

SaltedFig said:


> EDTA's aren't my thing, so up until now I didn't know that much about it (other than it's use in medical circles, prior to hearing about it in soaping) and I certainly didn't know it's function in plant growth (which has piqued my interest - I'm going to have a bit of a closer look at that ).
> 
> The thing that I didn't know, in the products you all use, is whether you are using the hydrate or anhydrous product, but I kind of concluded that it didn't actually matter (so long as the calculations were kept consistant), so I chose the hydrate version.
> 
> ...


 
I probably have no business trying all this, but it's fun. I have 2 questions.
1. Do you think KOH will work to convert the DiEDTA to TetraEDTA? (And if so, do I need to discount EDTA because of my 90% purity of KOH? Or is that so tiny it doesn't matter.)
2. And just in reference to reading your post, how does 21.5% translate to 1:5? Wouldn't it be closer to 1:4? What am I missing??

The reason I ask is because I have a LS paste I need to dilute. The recipe asks for it to be diluted with a 39% solution of TetraEDTA. I only have DiEDTA. If I can not use KOH to convert Di to Tetra and have to use NaOH instead and then add that solution diluted to 39% to my paste, will that cause problems since the paste was made with KOH?


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## emi (Dec 21, 2018)

DeeAnna said:


> Thank you, Carolyn! One data point from @cmzaha. Do you remember if it was at all difficult to dissolve the disodium EDTA?
> 
> I agree with sending white powder over the border, @Misschief. Thanks for the offer, but I think both of us will be happier if you don't.
> 
> I've got to run (DH needs oral surgery). I'll get a call-to-action thread started later today or tomorrow.



Oooh I want to test! I have Di and the Tetra's ETA is 1/7. I can send you some DiEDTA if you'd like. I'd love to return the favor of you answering all my pokey questions. Gonna keep an eye out for your call to action!


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## SaltedFig (Dec 22, 2018)

emi said:


> I probably have no business trying all this, but it's fun. I have 2 questions.
> 1. Do you think KOH will work to convert the DiEDTA to TetraEDTA? (And if so, do I need to discount EDTA because of my 90% purity of KOH? Or is that so tiny it doesn't matter.)
> 2. And just in reference to reading your post, how does 21.5% translate to 1:5? Wouldn't it be closer to 1:4? What am I missing??
> 
> The reason I ask is because I have a LS paste I need to dilute. The recipe asks for it to be diluted with a 39% solution of TetraEDTA. I only have DiEDTA. If I can not use KOH to convert Di to Tetra and have to use NaOH instead and then add that solution diluted to 39% to my paste, will that cause problems since the paste was made with KOH?



1/ Theoretically it should be possible.

By substituting the Sodium Hydroxide with Potassium Hydroxide, you would also need to account for the extra molecular weight of Potassium (Potassium is heavier than Sodium).

You can use the multiplier to change between NaOH and KOH for SAP value calculations (the SAP multiplier is a handy number to remember: 1.403).

If your purity is 90%, or 0.90, then you also need to divide by 0.90 to get the larger weight needed (to account for the lower purity).

I did some rough numbers for you, and the multiplier becomes 0.30, or 30%, by weight at 100% purity, or 0.33, or 33%, by weight for a 90% purity, for use with KOH.

2/ I calculated the multiplier to ensure that my checking of DeeAnna's numbers followed different steps (where possible).
The same sort of idea is used when checking addition of a list of numbers - the check is to add them up from the last to the first - just by changing the technique, the chance of duplicating errors is lowered.

Short answer:
5:1 ratio means that if you start with 5 parts of Disodium EDTA, you need 1 part of NaOH to react with it.
If you have 100 parts of Disodium EDTA, using this ratio, you'll need 20 parts of NaOH to react with it.
That means that you can take the Disodium EDTA weight, and multiply it by 20% to get the amount of NaOH needed.

The bit you were missing is the number juggle needed to go the other way, and convert a percentage (eg. 20%) into a ratio.
You need to convert your percentage to a decimal first (20/100 = 0.2).
Then you need to know how many of these are needed to make 1 (1/0.2 = 5)
The ratio is now known and can be expressed as 5:1
If you have a calculator or spreedsheet, the single line equation for this is:
1 / ("x%" /100), where "x%" is 20 in our example, so 1/(20/100) = 5
Note: The brackets are important.

Long answer:


DeeAnna said:


> ... The (very small) catch to using  Di is every 5 grams of Di will consume about 1 g NaOH. We use so little EDTA in soap that you might not feel the need to adjust for this -- it's such a tiny error. If you're a geek like me, however, you Want To Know These Things so you can decide.





DeeAnna said:


> ... I'm hoping maybe SaltedFig, GalaxyMLP, or someone else with a chemistry and math background will doublecheck my thinking. I think I've got the numbers straight, but it never hurts to get a second opinion.





emi said:


> ...
> 2. And just in reference to reading your post, how does 21.5% translate to 1:5? Wouldn't it be closer to 1:4? What am I missing??



The method I used to get the number was to work out the molecular weights, and then divide the molecular weight of NaOH by the molecular weight of Disodium EDTA to get the multiplier needed to calculate how much NaOH is needed for a given amount of Di.

The multiplier I got was 0.214898, which I rounded to 21.5% for our use.

The usage rate of 5g of Tetrasodium EDTA for 1000g of oil is a usage rate that DeeAnna described in an earlier post (it is slightly irrelevant from my perspective - I don't use EDTA, so I take your usage rate at face value), but I'll use this amount as a way of describing the "vast" impact of these numbers 

Superfat example
1000 grams of Olive Oil has a NaOH saponification value of 0.136 (roughly) . This gives 136grams of NaOH for a zero superfat. For a 5% "superfat", this amount is multiplied by 95% (or 0.95), to give 129 grams of NaOH).

If 5g of Tetrasodium EDTA, and 0.215 is the multiplier to calculate the extra NaOH to convert Disodium EDTA to Tetrasodium EDTA, then there is another 1g of NaOH required.

The extra superfat created, if this 1g of NaOH is not included, is just over 1%. Just about all recipes will be in the range of a superfat increase of 1% to 2%.

Conclusion:
It's probably worth adding the extra hydroxide if you are using Disodium EDTA, but not entirely necessary.

Original Tetrasodium EDTA: 1000g of oil, 5g of Tetrasodium EDTA
Disodium version with NaOH: 1000g of oil, 5g of Disodium EDTA and 1g additional NaOH
Disodium version with KOH: 1000g of oil, 5g of Disodium EDTA and 1.5g additional KOH
Disodium version with KOH: 1000g of oil, 5g of Disodium EDTA and 1.6g additional 90% KOH

I hope DeeAnna (or one of our other resident chemists) will be so kind as to check my thinking on emi's KOH idea?

Anyway - I might leave this all to you that use EDTA.
Good luck!


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## DeeAnna (Dec 22, 2018)

@emi -- You should be able to react disodium EDTA with KOH. Use the same weight of Di as you would Tetra. The reaction of KOH and Di will consume about 1.4 grams of KOH for every 5 grams of Di that you add.

***

I'm feeling overwhelmed at the moment, so SMF is going to have to take a back seat for a few days. My son has just arrived for a couple of days visit. My estranged stepson and his new wife JUST emailed asking to visit Sunday through Monday morning. I have a dog coming home today from having had knee surgery and has a very restricted range of activities for the next couple of weeks. 

Life has zoomed from zero to 60 all of a sudden. So I'm not ghosting y'all ... just way too busy.


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## emi (Dec 23, 2018)

SaltedFig said:


> 1/ Theoretically it should be possible.
> 
> By substituting the Sodium Hydroxide with Potassium Hydroxide, you would also need to account for the extra molecular weight of Potassium (Potassium is heavier than Sodium).
> 
> ...



Wow. Thank you so so much. My brain is fried. I've been crunching numbers for the last 3+ hours learning all kinds of things. Found myself needing to get solid grip on SAP values which led me on a looptyloop with what I'm sure are typos on someones website trying to explain it which led me all the way back to refreshing college chem 101 with youtube vids on moles and the periodic table....and I've gotten though a little over half your reply. But I'm finally confident to proceed with this LS dilution. I caught so many mistakes in my previous calculations! And I now totally understand what I was missing with the 5:1 thing. I was actually confused and asking about the same exact concept that started this thread that DeeAnna answered so well. I think I get it now. percentage of the SOLUTION vs SOLVENT. In the EDTA case, its 21% NaOH of EDTA as if EDTA is like "solvent", not "solution" of both combined. where 5:1 represents the whole solution. (Like bread hydration of flour = "Solvent"). So if 10g of EDTA, 2.1 g is 21.5%of NaOH. anyway, I think I got it. I hope I got it. I'm going to get this paste going, then digest the SF section of your reply tomorrow with a fresh brain! Thank you so much again for taking the time to post this. I'm sure many will benefit from it in the future! 
. 




That zip lock bag is my paste and that big printed packet is IrishLass's 30+ page recipe (with minimized pics!)


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## Juhi (Nov 18, 2019)

DeeAnna said:


> Disodium EDTA can be converted into Tetrasodium EDTA by reacting the Di with NaOH or other strong alkali. I strongly suspect it's as simple as measuring the correct amount of powdered Di and adding it to your lye solution. Di won't dissolve in plain water like Tetra will, but it should dissolve in lye solution and react with the NaOH to form Tetra.
> 
> I haven't done the calculations, so I don't have solid numbers at the moment about how much Di to use and how much NaOH it will consume as it converts to Tetra. Here's a link to what appears to be some reputable although not very detailed advice -- https://chemistscorner.com/cosmetic...-to-formulate-tetrasodium-edta-and-etidronate
> 
> ...



I too need tp convert disodium EDTA to tetra sodium EDTA.

My recipe calls for a miniscule amount of tetrasodium EDTA. I have to use NaOH solution in the initial steps as well. Can I simply add disodium EDTA in NaOh solution (50% NaOH which will be more than 1 part per 5 part if disodium EDTA, as the amount of NaOH is going to be 10 times or more than the amount of EDTA needed)


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## emi (Nov 25, 2019)

Sorry for the late reply! Yes, I just added the DiEDTA into the lye water with the appropriate amount of lye to convert it. I can't remember the exact numbers but in terms of process that is what I did. But honestly it's impossible for me to tell if it "worked"! It was for a liquid soap recipe and really how would I know if the EDTA did its job or not? I learned a lot on the process though and I do have fun geeking out from time to time. But I also do have really hard water and I figured the tetra will be useful in future recipes, so after going through the Di to Tetra conversion which I hope worked, I went ahead and bought a small pack of the Tetra EDTA on amazon. It looks like amazon doesn't carry it anymore, but it was coming from Making Cosmetics which does still carry it. Below is a link to the TetraEDTA for $5 from Making Cosmetics.
https://www.makingcosmetics.com/EDTA_p_238.html

DeeAnna is very knowledgable about the actual chemistry of soap making. I have learned so much from her alone. Below is a link that might not tell you too much about converting, but it is a page from DeeAnna's website that talks about EDTA. I referenced this page quite a lot when making my laundry soap. 
https://classicbells.com/soap/EDTA.asp


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