Sodium citrate from baking soda and citric acid

[DeeAnna]

Actually, what's wrong with using sodium citrate as a water-based solution? Maybe the universe is pointing the way for you to use it that way rather than in solid form? After all, you're just going to dissolve the citrate in water later on when you make soap.

You know what weight of citric acid you started with. Assuming you used exactly the right amount of baking soda or a slight excess of baking soda, you can reasonably assume all of the citric acid converted to sodium citrate. Using Galaxy's relationship of "..1 gram of citric acid (CA) is neutralized with 1.3124 grams of baking soda (BS)...." then you can figure out the total weight of sodium citrate. The rest is water and maybe a little leftover baking soda -- but for all intents and purposes let's call it 100% water. Based on what I'm seeing on Google, you should be able to make a 50% solution by weight. That means to dissolve 100 grams of sodium citrate in 100 grams of water to make a total of 200 grams of solution.

ETA: 1 g citric acid + 1.31 g baking soda => 1.34 g sodium citrate + carbon dioxide gas + water. See also post 51 below.

 

[TeresaT]

Actually, what's wrong with using sodium citrate as a water-based solution? Maybe the universe is pointing the way for you to use it that way rather than in solid form? After all, you're just going to dissolve the citrate in water later on when you make soap.

You know what weight of citric acid you started with. Assuming you used exactly the right amount of baking soda or a slight excess of baking soda, you can reasonably assume all of the citric acid converted to sodium citrate. Using Galaxy's relationship of "..1 gram of citric acid (CA) is neutralized with 1.3124 grams of baking soda (BS)...." then you can figure out the total weight of sodium citrate. The rest is water and maybe a little leftover baking soda -- but for all intents and purposes let's call it 100% water. Based on what I'm seeing on Google, you should be able to make a 50% solution by weight. That means to dissolve 100 grams of sodium citrate in 100 grams of water to make a total of 200 grams of solution.

This made my brain hurt. I don't know why I made it powder, either, except that's what Galaxy did and I'm a copycat. The only thing I can think of is to get all of the sodium citrate separated from the water so that I *could* make a 50% solution by weight. If I used the wet or damp stuff, my solution concentration would be off, wouldn't it? Also, if I used wet or damp stuff in my soap, wouldn't that make my usage rate off? My brain really hurts now.

Drying now. I'll see tomorrow how much I ended up with after all of my mistakes. But, it was fun learning how to make a real chemical in my kitchen.

 

[galaxyMLP]

What Dee says would probably be best in the future. I'll probably honestly do that from now on. In my head though, I liked the idea of having a dry powder instead of yet another jar of liquid in my tiny (carpeted) apartment.

If you have the room for it, I would say go for it if evaporating it isn't working for you. She's right you know, you ARE just going to dissolve it again.

Dee, the voice of reason.

Also, I'm VERY sorry this didn't work for you it makes me sad when other people have a hard time due to something I wrote or had a hand in. Again, I'm sorry.

 

[commoncenz]

Actually, what's wrong with using sodium citrate as a water-based solution? Maybe the universe is pointing the way for you to use it that way rather than in solid form? After all, you're just going to dissolve the citrate in water later on when you make soap.

You know what weight of citric acid you started with. Assuming you used exactly the right amount of baking soda or a slight excess of baking soda, you can reasonably assume all of the citric acid converted to sodium citrate. Using Galaxy's relationship of "..1 gram of citric acid (CA) is neutralized with 1.3124 grams of baking soda (BS)...." then you can figure out the total weight of sodium citrate. The rest is water and maybe a little leftover baking soda -- but for all intents and purposes let's call it 100% water. Based on what I'm seeing on Google, you should be able to make a 50% solution by weight. That means to dissolve 100 grams of sodium citrate in 100 grams of water to make a total of 200 grams of solution.

Question ... never mind ... I was going to ask if, since you usually dissolve sodium citrate in a 2:1 solution, wouldn't you then have to add extra water before adding to your oils?

However, if you have completely dissolved your sodium citrate in a 1:1 solution, you wouldn't have to do this. You'd just weigh out your solution so that you have the correct amount of sodium citrate for your recipe and account for the water by discounting that amount from your lye solution ... So, if your recipe called for 1.7 Oz of sodium citrate, you would weigh out 3.4 Oz of solution, which would be 1.7 Oz of both water and sodium citrate. Then you would account for the 1.7 Oz of water by discounting that amount from your lye solution ... correct?

(still using Oz here 'til I get a scale that goes down to the .01 grams)

 

[galaxyMLP]

Yeppers. Exactly that.

Remember that about 30 grams are in 1 oz so a scale that can weigh up to 0.05 oz is still better off being used in grams b/c that is actually more accurate. Even if you round to the gram, its better than 0.1 oz.

 

[TeresaT]

What Dee says would probably be best in the future. I'll probably honestly do that from now on. In my head though, I liked the idea of having a dry powder instead of yet another jar of liquid in my tiny (carpeted) apartment.

If you have the room for it, I would say go for it if evaporating it isn't working for you. She's right you know, you ARE just going to dissolve it again.

Dee, the voice of reason.

Also, I'm VERY sorry this didn't work for you it makes me sad when other people have a hard time due to something I wrote or had a hand in. Again, I'm sorry.

Silly girl! Don't be sorry! This was all good. It's an experiment. I'll try it again and do better next time. (By that, I mean stay in the kitchen where the boiling pot is and off the internet!). You're a scientist. You know not everyone gets it right the first time out.

I'm still trying to wrap my brain around the solution thingy. What would have been the usage rate of the liquid I ended up with in the first place? I mixed 200 mg CA with 263 mg BS in 400 mg water. So, once all of it stopped reacting what was in my pot? Would there still have been 863 mg of "stuff" in my pot and how much of that would be SC and how much H2O. Oh, no. My brain hurts again.

 

[DeeAnna]

Teresa ... the amount of citrate you made can be calculated based on the citric acid you weighed out to begin with ... you don't have to dry the stuff out to get that weight.

Gosh ... I'm on my kindle right now (lying in bed totally goofing off, if you must know) and don't have my calculator close to hand. I need to sit down tomorrow at my desk (where I left my geek hat for the night) and figure this out for you. Or Galaxy can if she's so inclined!

 

[DeeAnna]

The final weight of stuff won't equal the weight of what you started with cuz some of it fizzed off or evaporated into the air.

 

[galaxyMLP]

The theoretical yield (amount of sodium citrate I should end up with) for the amount of CA and BS I originally used was 268 g. I got 321 g because I couldn't get all the water to evaporate. Not bad though.

That is what you are looking for. So in this case, you would do a solution with 268 grams of water with your initial 200 g CA and 263 g BS. That gives you 268 g of SC, which has to be at least 50% concentration. I hope that helps! I'm off to bed not though so I'll have to answer any other questions in the morning.

 

[TeresaT]

DeeAnna, don't worry about it. I don't want you to go through more trouble than you already have. I weighed my sodium citrate a little while ago. I have 99 gm! When that water "softened" up the caked stuff on the bottom of the pot, it probably dissolved some of it. And when I poured it through the strainer to catch the chunks, I probably should have saved that "water."

I really should not do "brainpower" stuff after working all day. That is why I only soap on the weekends and quit cooking a few years ago.

 

[DeeAnna]

Hey, Teresa, good save! After a cuppa joe this morning, I rummaged around, found my geek hat and paraphernalia, and re-read Galaxy's original post. She did all the math for us already!

Galaxy's original recipe:

400 g distilled water
200 g citric acid
263 g baking soda

After following her procedure for mixing this up, the chemical reaction will create 268 g trisodium citrate (aka sodium citrate). When you get the baking soda all dissolved and everything stops fizzing, you'll have 268 g sodium citrate plus some water and perhaps a bit of leftover baking soda.

If you don't want to evaporate the citrate to a dry powder, I would suggest making a 50% sodium citrate solution. To do this:

Weigh the solution you've just made. The weight of water in the solution after everything is all reacted will be:
After-the-reaction water weight = Total solution weight - 268 g of sodium citrate

If you add enough extra water to this mixture so the total water is equal to 268 g, then you will have a 50% solution of sodium citrate. In other words:
Water to add to make a 50% solution = 268 g - After-the-reaction water weight

***

To scale this recipe up or down, you can use this relationship:

1 gram citric acid plus 1.31 g baking soda gives you 1.34 g sodium citrate.

***

To use, figure the weight of pure sodium citrate you want to add to your soap batch. Since every gram of your solution has only 0.5 g of citrate, use TWO TIMES that weight when measuring out your 50% sodium citrate solution.

What dosage of citrate to use in soap? A typical dosage for citric acid is about 1% ppo. The equivalent dosage of sodium citrate is 1.3% ppo. You can do 2 or 3 times that amount, if needed.

 

[galaxyMLP]

I was hoping you would see that! I also quoted it in the post I made last night. Thank you for elaborating.

 

[commoncenz]

I guess it probably doesn't matter since I will most likely stick with Galaxy's numbers. However, how did you come to 400 ml of water originally? Also, if I am doing my math correctly one could expect a conversion rate of roughly 0.58? By that I mean your yield of sodium citrate will be approximately equal to .58 of the total weight of CA and BS you used to create the sodium citrate.

 

[galaxyMLP]

I guess it probably doesn't matter since I will most likely stick with Galaxy's numbers. However, how did you come to 400 ml of water originally? Also, if I am doing my math correctly one could expect a conversion rate of roughly 0.58? By that I mean your yield of sodium citrate will be approximately equal to .58 of the total weight of CA and BS you used to create the sodium citrate.

Sometimes in life, numbers just come to us. I just wanted some amount that my CA and BS could be easily dissolved in and I picked 400 g. Its completely arbitrary in this case. No math was done to get the magical number of 400.

I don't want to comment on the conversion rate yet (it should work but, just to make sure, I want to do more maths).

 

[commoncenz]

Sometimes in life, numbers just come to us. I just wanted some amount that my CA and BS could be easily dissolved in and I picked 400 g. Its completely arbitrary in this case. No math was done to get the magical number of 400.

I don't want to comment on the conversion rate yet (it should work but, just to make sure, I want to do more maths).

Sounds totally fair. Please let us know when you have arrived at a conclusion. And again, thanks for this.

 

[TeresaT]

Thank you! That makes sense now. I can wrap my little-bitty brain around that math explanation! I have actually found and ordered food grade SC; however, now that I understand better the idea behind making the solution, I'm going to play with it a little more. Just because CA & BS are readily available at Ace hardware and if I can learn to make my own solution, I won't ever have to worry about running out.

 

[Dahila]

I have a difficulties with the 50% solution. Half of that is water yes? Am I wrong? Let's say I am adding SC solution but 25% of that is water? Help me out wise woman)

 

[galaxyMLP]

Sorry, I'm a little confused by your question.

Do you mean, what if you have a 25% solution of SC?

In that case you have 1 part SC to 3 parts water.

However, the way you wrote it (25% of that is water) , I read it as you are trying to dissolve 3 parts SC in 1 part water which is not possible?

ETA: and yes, for a 50% solution, half of it is water.

 

[DeeAnna]

"...Half of that is water yes? Am I wrong?..."

You are right -- that is correct, Dahlia.

"...Let's say I am adding SC solution but 25% of that is water?..."

I don't think it is possible to make a 75% solution of sodium citrate and 25% water. I think a 50% solution is about the most concentrated sodium citrate solution possible.

***

So let's talk about a more practical solution of 25% citrate and 75% water. If that is the case, then here is an example of how to calculate the amount of solution to use in your recipe --

Example: You want to add 10 grams of pure sodium citrate to a soap recipe. If you are using a 25% solution of sodium citrate, then you would add this much citrate solution:
Weight of 25% citrate solution = (100 / 25) x 10 grams = 40 grams.

See how the 25 percent is used as a fraction in this example? You can simplify the fraction "100/25" to just "4" if you like. The number "4" is certainly easier to remember, but not every percent works out this nicely. Bear with me and look at this next example --

***

If you COULD make a 75% solution of sodium citrate in water -- just pretending here -- then the math to get a total of 10 grams of sodium citrate using a 75% solution is this:
Weight of 75% citrate solution = (100 / 75) * 10 grams = 13.3 grams.

The fraction of 100/75 doesn't make a nice easy number like the previous example of 100/25, so the fraction of "100/75" is probably the easiest to use in this case.

***

You can use the same method with a 50% solution that we've been talking about in previous posts. Here is an example of how to calculate the correct amount of sodium citrate if using a 50% solution --

Example: You want to add 10 grams of pure sodium citrate to a soap recipe. If you are using a 50% solution of sodium citrate, then you would add this much citrate solution:
Weight of 50% citrate solution = (100 / 50) x 10 grams = 20 grams.

Again, the fraction of 100/50 can be simplified to a convenient "2" that is easier to remember. This 50% example and the 25% example show you why people tend to stick to these percentages rather than using other percentages. The math is easier.

I hope this helps.

ETA: Please note the maximum concentration for sodium citrate in water is roughly 40% -- 40 grams SC + 60 grams water. Many thanks to Patrick for providing this information -- see Post 71 below. I updated my original recipe -- see Post 83 for the latest version.

 

[jiroband]

I'm sorry for interrupting from out of no where, but what are you making sodium citrate for?

I tried to follow this from the beginning, but I must have gotten lost along the way.