Calculating ca in dual lye recipe

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madison

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Hello everyone,
I am trying to figure out how to calculate the amount of citric acid in a dual lye soap bar recipe if it makes sense; I have been reading a lot of threads but I couldn’t come across that piece of information. If there is a thread already there please post it for me here. Thanks in advance.
 
You could make it more simple - how much ca do you need? How much NaOH does that need? Then put that much extra NaOH in to the water with only the NaOH at first and add the ca. Then you have your target amount of NaOH for your dual lye mixture and the correct amount of sodium citrate. Then add your KOH in to that solution
 
Sodium citrate and citric acid? I thought citric acid ends up as sodium citrate when lye goes through lye. So in my thinking, using both sodium citrate and citric acid will mean more sodium citrate in the finished soap. Is this correct? This chemistry lessons get quite complicated. Please someone......help
 
The Efficacious Gentleman said:
You could make it more simple - how much ca do you need? How much NaOH does that need? Then put that much extra NaOH in to the water with only the NaOH at first and add the ca. Then you have your target amount of NaOH for your dual lye mixture and the correct amount of sodium citrate. Then add your KOH in to that solution
Click to expand...

I like this solution. It is very elegant and simple. For a good reference on making sodium citrate, look here: https://classicbells.com/soap/citrate.html

Forgot to add: DeeAnna, a major contributor to this forum, has a lot of great information on soaping at her classicbells.com website, so folks should just go over there and poke around sometime.
 
Last edited:
smengot0 said:
Sodium citrate and citric acid? I thought citric acid ends up as sodium citrate when lye goes through lye. So in my thinking, using both sodium citrate and citric acid will mean more sodium citrate in the finished soap. Is this correct? This chemistry lessons get quite complicated. Please someone......help
Click to expand...



Kind of.

With a single lye recipe you add in citric acid and increase the lye by enough that reacts with the citric acid to make sodium citrate. That is simple enough.

So you put citric acid and more NaOH in to get NaOH and sodium citrate at the end, no citric acid remains.

In the first post, I was saying that you can do that with just the NaOH part of your recipe and then add in the KOH.
 
The Efficacious Gentleman said:
You could make it more simple - how much ca do you need? How much NaOH does that need? Then put that much extra NaOH in to the water with only the NaOH at first and add the ca. Then you have your target amount of NaOH for your dual lye mixture and the correct amount of sodium citrate. Then add your KOH in to that solution
Click to expand...

Thank you, this is simple, I thought maybe I should count the ca for KOH as well, this is why I needed help. Does the same apply when making LS with a little amount of NaOH?
 
smengot0 said:
Sodium citrate and citric acid? I thought citric acid ends up as sodium citrate when lye goes through lye. So in my thinking, using both sodium citrate and citric acid will mean more sodium citrate in the finished soap. Is this correct? This chemistry lessons get quite complicated. Please someone......help
Click to expand...

He didn't mean to add sodium citrate, he meant that the reaction between citric acid and NaOH will give the sodium citrate.
 
The Efficacious Gentleman said:
Kind of.

With a single lye recipe you add in citric acid and increase the lye by enough that reacts with the citric acid to make sodium citrate. That is simple enough.

So you put citric acid and more NaOH in to get NaOH and sodium citrate at the end, no citric acid remains.

In the first post, I was saying that you can do that with just the NaOH part of your recipe and then add in the KOH.[/QUOTE

This post didn't show on my screen until I posted my reply, thank you Graig.
Click to expand...
 
What The Gent said.

Decide on how much citric acid you want to use, and calculate the NaOH needed to react with the citric acid. Set that problem aside -- it's done.

Design the soap recipe and the NaOH and KOH needed for the soap.

Add the weight of the NaOH for the citric acid to the NaOH for the soap. That's how much total NaOH you will need. The KOH needed is just the weight of KOH you calculated for the soap.

In other words, don't "dual lye" the citric acid part. I need to update my citric acid article about this -- that is the link that Scooter posted.
 
Thanks Madison/DeeAnna. Yes DeeAnna, kindly update your citric acid article to reflect this part. I actually follow your guidelines closely when I use ca. Thanks again
 
DeeAnna said:
What The Gent said.

Decide on how much citric acid you want to use, and calculate the NaOH needed to react with the citric acid. Set that problem aside -- it's done.

Design the soap recipe and the NaOH and KOH needed for the soap.

Add the weight of the NaOH for the citric acid to the NaOH for the soap. That's how much total NaOH you will need. The KOH needed is just the weight of KOH you calculated for the soap.

In other words, don't "dual lye" the citric acid part. I need to update my citric acid article about this -- that is the link that Scooter posted.
Click to expand...

Thank you DeeAnna, I was thinking about"dual lye" the ca, it turned that the calculations are much easier than what I thought. I understand now that the KoH shouldn't be touched in order to get the"magic"of it.:)
I would like to know if I just dry the citric acid in the oven do I get anhydrous ca? Is that all the process? I need some to check the purity of two used bottles of NaoH and KOH that I have forgotten about them in my garage. I will be following your method. Thank you for all your help, I am appreciated.
 
Scooter said:
I like this solution. It is very elegant and simple. For a good reference on making sodium citrate, look here: https://classicbells.com/soap/citrate.html

Forgot to add: DeeAnna, a major contributor to this forum, has a lot of great information on soaping at her classicbells.com website, so folks should just go over there and poke around sometime.
Click to expand...

I do that, I have done that plenty of times to better understand many points that were complicated to me, look like I am falling in love with chemistry because I am understanding more, I used to feel like one of those chemistry dummies. All thanks to DeeAnna, I appreciate all her efforts and knowledge. Thanks to everyone who helps as well here on the forum, thank you scooter for pointing this out.
 
Last edited:
I love this forum. So much to learn from you all. And everyone is so very generous. Thanks
 
"...I would like to know if I just dry the citric acid in the oven do I get anhydrous ca? Is that all the process?..."

That's the essence, yep. You want to gently heat the citric acid until its weight is stable from one weighing to the next. As long as the weight is dropping while you heat the citric acid, that means water is still being driven off, and the citric acid is not yet anhydrous.

***

I've updated my soapy articles today including an explanation about calculating the alkali needed when making a dual-lye recipe with added acid. The method is in the "Calculating a dual lye (KOH and NaOH) recipe". I put a link in each of in all of the articles about the various acids that connects them to this "Dual lye" article.
 
DeeAnna said:
"...I would like to know if I just dry the citric acid in the oven do I get anhydrous ca? Is that all the process?..."

That's the essence, yep. You want to gently heat the citric acid until its weight is stable from one weighing to the next. As long as the weight is dropping while you heat the citric acid, that means water is still being driven off, and the citric acid is not yet anhydrous.

***

I've updated my soapy articles today including an explanation about calculating the alkali needed when making a dual-lye recipe with added acid. The method is in the "Calculating a dual lye (KOH and NaOH) recipe". I put a link in each of in all of the articles about the various acids that connects them to this "Dual lye" article.
Click to expand...
Thank you for the update and for answering my question.
 
DeeAnna said:
"...I would like to know if I just dry the citric acid in the oven do I get anhydrous ca? Is that all the process?..."

That's the essence, yep. You want to gently heat the citric acid until its weight is stable from one weighing to the next. As long as the weight is dropping while you heat the citric acid, that means water is still being driven off, and the citric acid is not yet anhydrous.

***

I've updated my soapy articles today including an explanation about calculating the alkali needed when making a dual-lye recipe with added acid. The method is in the "Calculating a dual lye (KOH and NaOH) recipe". I put a link in each of in all of the articles about the various acids that connects them to this "Dual lye" article.
Click to expand...



Thanks for updating your soapy articles DeeAnna. Appreciate.
 

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