Natural glycerin in CP soap

[LBussy]

"...How much glycerin is produced using 1g of the 90% KOH sold by Essential Depot? ..."

I'm going to give you the set-up for this problem. See if you can come up with the answer, okay?

First thing to know is the chemical conversion between the two lyes:
1 g of NaOH is the equivalent of 1.4 g of KOH.
Said another way, 1 g of KOH is the equivalent of 0.7 g NaOH.

I have already said that 1 g of NaOH will produce 0.77 g of glycerin, so there's another piece of the puzzle.

First, figure the "ideal" amount of glycerin produced by 100% pure KOH.

Next, figure the glycerin for impure KOH. For a 90% purity KOH, the glycerin it can make is 90/100 of the ideal.

Hopefully this is right .. I spent the morning crunching numbers for pyro in a similar manner but had to start with atomic/molar weights. My brain hurts.

If NaOH and KOH are in a 1:1.4 ratio, then 1g of KOH should produce 0.55g glycerin. Then if we assume 90% KOH, 1g of KOH would produce 0.495g.

Do I win a prize?

 

[DeeAnna]

Well done!

 

[cpacamper]

"...How much glycerin is produced using 1g of the 90% KOH sold by Essential Depot? ..."

I'm going to give you the set-up for this problem. See if you can come up with the answer, okay?

First thing to know is the chemical conversion between the two lyes:
1 g of NaOH is the equivalent of 1.4 g of KOH.
Said another way, 1 g of KOH is the equivalent of 0.7 g NaOH.

I have already said that 1 g of NaOH will produce 0.77 g of glycerin, so there's another piece of the puzzle.

First, figure the "ideal" amount of glycerin produced by 100% pure KOH.

Next, figure the glycerin for impure KOH. For a 90% purity KOH, the glycerin it can make is 90/100 of the ideal.

Deanna, your posts on this thread are a real education. THANK YOU for sharing.

I was out of town over the weekend and did not have the chance to browse the forum while I was gone

I promise I did not look at Lee's answer before making my calculations

On my handy dandy CPA-type adding machine, I divided 1g NaOH/1.4KOH = .714285, so 1 g KOH is equivalent to .714285 NaOH for this calculation.

Then, .714285 NaOH equivalent x .77g glycerin produced by 1g NaOH = .549999.

So, 1g KOH produces .549999g glycerin.

Multiply .9 for 90% ED KOH x .54999 = .49499.

1g of my 90% KOH produces .49499g glycerine while 1g NaOH produces .77g glycerin.

Peeking at Lee's answer now.

Follow up thought:

According to soapcalc, it takes 17.408g of pure NaOH or 24.415g of pure KOH to saponify 100g of coconut oil. Applying the above calculated results means either lye will produce essentially the same amount of glycerin (17.408g NaOH x .77 = 13.404g glycerin; 24.415g KOH x .54999 = 13.42800g glycerin). This makes sense to me if it's true.

 

[LBussy]

Applying the above calculated results means either lye will produce essentially the same amount of glycerin.

Correct - it has to.

 

[DeeAnna]

Yes, you are right. The two lyes create the same amount of glycerin -- one molecule of either lye makes 1 molecule of glycerin.

Since one molecule of KOH weighs 1.4 times as much (1.403, to be more precise) as one molecule of NaOH, there's a weight difference, but an equal number of molecules of either lye is needed.

I'm doing some rounding, in case y'all are wondering why the results are not coming out exactly the same.

 

[cpacamper]

I love the elegance of the repeating decimal in the fraction 5/7 (1/1.4): .714285714285714285714285...hehehe