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This message was posted by a user wishing to remain anonymous

We are looking at some new vendors for our chemicals at the moment, and I am a little confused.  Sorry for the long post.

The new vendor is offering a few different concentrations of caustic.  One of which the claim is "60% w/w".  We got a sample of this, which I titrated with phenolphthalein using 7.7N HCl.  I ended up with 42% caustic as NaOH, after titrating this a number of times.  I pulled a sample of caustic from our current supplier and it was the concentration I expected.  After talking with the new vendor, they assured me that what I am getting is really 60% w/w, but they could also offer us a 98% caustic that would end up being much cheaper.  Now I am completely confused. 

Is it possible to get a 98% caustic solution?  This particular solution has 1.5% gluconate added as well.  Can you basically make a caustic solution with only sodium gluconate and 0.5% w/w of something else?  I always thought the sodium gluconate was there as a surfactant, can it increase the solubility of the NaOH to 98%?  From googling around, it seems the solubility limit for NaOH in pure water would only be about 52% w/w, but there are stronger caustic solutions available than that, so I assume there is something you can add to increase the solubility?  

Is it possible that I can't titrate the caustic the way I am doing it with phenolphthalein and HCl?  I diluted it 1:10 and 1:2 and got the same results each time.  I am confident that the titration kit I am using (drop kit, not with a burette) is still good and filled with accurate chemicals.  

Could we test the concentration by density and get within a +/- 2% to confirm the titration results with a separate method?  I don't know how much of the other additives are in the caustic, so I am not sure if it is possible to test the concentration that way since it isn't a binary solution.  

I am looking for any explanation of what I could be doing wrong here, since the only other explanation I can come up with is that the vendor is sending out caustic that is not as strong as they claim.  We don't typically test caustic as we receive it, and wouldn't normally catch this since our CIP system would just add enough of the caustic to hit the required conductivity.  We do regularly test the working strength caustic in the CIP skids to ensure we don't have carbonate forming, but this wouldn't tell us if the caustic we are purchasing isn't the strength we think it is.  We go through enough chemicals that we wouldn't catch a variance in strength by an increase in usage/ordering.  Do other people regularly test their incoming caustic to ensure they are the correct strength?  I used to test bulk sulfuric acid by density at very large brewery, but that was a binary mixture (water and sulfuric acid) being used for water treatment, and we never tested the bulk caustic or the cleaning acid blend there (as far as I know).

Thanks in advance for your responses! 

The maximum limit for commercially available sodium hydroxide (NaOH) is 50% w/w.  You can get a good idea of how much caustic is in the concentrate by checking the specific gravity. 50% NaOH has a specific gravity of approximately 1.53, which works out to about 12.75 lbs. per gallon, and will freeze solid at about 60 d. F.

If you take 50% x .6, you come up with 30% as NaOH, which is common strength for brewery CIP caustic solutions with gluconate (a chelator, not surfactant).  I presume the 98% version that is cheaper is nothing more than straight sodium hydroxide without the gluconate added.  Hope this helps.  Please feel free to reach out to me if you have any questions or need anything else.

------------------------------
Dana Johnson He/Him
Sector Specialist, Craft Brewing
Diversey - A Solenis Company
Henderson, CO
800.233.1000
------------------------------

When comparing chemicals, there are a few things to watch out for.  Chemical vendors will give recommended use concentrations generally in one of two ways.  Either as percentage active ingredient (e.g. 2% NaOH) or in percent by weight or volume (% v/v or w/w).  Percent by weight is generally only used when using solid products since it is difficult to measure solids in volume and water has a set weight of 8.33 lbs/Gallon.  Caustic as a concentrate is given in percent by weight or as percent active NaOH.  The solubility limit of Sodium Hydroxide is just above 50%, as you already correctly stated.  There is no 60% NaOH in liquid form.  There are 98% flakes or beads, but these are solid products.

You can measure Sodium Hydroxide strength by density; however, this would assume that the product is pure Sodium Hydroxide without any additional compounds added.  Your NaOH titration is in fact the best way to determine the concentrate strength of your caustic cleaner.

A table with conversion of active NaOH to specific gravity can be found here:

www.handymath.com/cgi-bin/naohtble3.cgi?submit=Entry

What you are looking at here is your basic chelated caustic CIP cleaner, which is not very cost effective. These products are generally used at concentrations between 2 - 5% NaOH in order to be effective.  At 42% active NaOH, this would translate to 4.8 - 11.9% by volume.  In comparison, a modern built CIP product like those sold by us is used at concentrations between 1 - 3% by volume.

I am assuming that this is a liquid product. If so, there is no possible way for the product to be above 50% active NaOH.  Concentrations above 50% are only possible with solid products.

I hope this helps and please send me an e-mail if you want some information about brewery specific CIP products.  My contact info is in my signature.      

Cheers,

------------------------------
Dirk Loeffler
Exec. VP of Technical Operations
SEKA Chemicals, LLC
loeffler.dirk@sekachemicals.com
------------------------------

An extension of this confusion is the test kits some vendors provide to check the strength of your working solution.  We had a vendor who's titration test kits worked accurately, but gave results in "% caustic".  To me, that suggests % NaOH (w/w).  When I reached out to our rep for clarity, he didn't seem to really understand what I was asking.  So I set up some titrations with my own reagents and determined that the test kit's "% caustic" results meant percent (v/v) of the liquid concentrate they sold us (which was about 30% w/w NaOH).

I agree with Dr. Bath that you should trust your own lab work over the word of any vendor- however well-intended they might be.  Also, avoid confusion at your facility by using clear language.  State concentration specifically as "weight percent NaOH" or "volume percent product XYZ" or "molarity" or "normal"; just anything but "% caustic"!

------------------------------
Cullen Dwyer
Brewer/Cellar/QA
Finestkind Brewing
Westminster MA
(978) 874-9965x1160
Brewer/Cellar/QAFinestkind BrewingFinestkind BrewingBrewer/Cellar/QABrewer/Cellar/QA
------------------------------

Original Message:
Sent: 06-04-2024 13:37
From: Dirk Loeffler
Subject: Comparing Caustic from different Vendors

When comparing chemicals, there are a few things to watch out for.  Chemical vendors will give recommended use concentrations generally in one of two ways.  Either as percentage active ingredient (e.g. 2% NaOH) or in percent by weight or volume (% v/v or w/w).  Percent by weight is generally only used when using solid products since it is difficult to measure solids in volume and water has a set weight of 8.33 lbs/Gallon.  Caustic as a concentrate is given in percent by weight or as percent active NaOH.  The solubility limit of Sodium Hydroxide is just above 50%, as you already correctly stated.  There is no 60% NaOH in liquid form.  There are 98% flakes or beads, but these are solid products.

You can measure Sodium Hydroxide strength by density; however, this would assume that the product is pure Sodium Hydroxide without any additional compounds added.  Your NaOH titration is in fact the best way to determine the concentrate strength of your caustic cleaner.

A table with conversion of active NaOH to specific gravity can be found here:

www.handymath.com/cgi-bin/naohtble3.cgi?submit=Entry

What you are looking at here is your basic chelated caustic CIP cleaner, which is not very cost effective. These products are generally used at concentrations between 2 - 5% NaOH in order to be effective.  At 42% active NaOH, this would translate to 4.8 - 11.9% by volume.  In comparison, a modern built CIP product like those sold by us is used at concentrations between 1 - 3% by volume.

I am assuming that this is a liquid product. If so, there is no possible way for the product to be above 50% active NaOH.  Concentrations above 50% are only possible with solid products.

I hope this helps and please send me an e-mail if you want some information about brewery specific CIP products.  My contact info is in my signature.      

Cheers,

------------------------------
Dirk Loeffler
Exec. VP of Technical Operations
SEKA Chemicals, LLC
loeffler.dirk@sekachemicals.com
------------------------------

It is important to distinguish between total product % (what some may call total caustic percentage) and total active caustic%. The best measurement to use when titrating a majority caustic solution is total active caustic% as this tells you how much of the solution is actually providing cleaning impact. 

------------------------------
Max Purzak
Ecolab
------------------------------

Original Message:
Sent: 06-05-2024 13:03
From: Cullen Dwyer
Subject: Comparing Caustic from different Vendors

An extension of this confusion is the test kits some vendors provide to check the strength of your working solution.  We had a vendor who's titration test kits worked accurately, but gave results in "% caustic".  To me, that suggests % NaOH (w/w).  When I reached out to our rep for clarity, he didn't seem to really understand what I was asking.  So I set up some titrations with my own reagents and determined that the test kit's "% caustic" results meant percent (v/v) of the liquid concentrate they sold us (which was about 30% w/w NaOH).

I agree with Dr. Bath that you should trust your own lab work over the word of any vendor- however well-intended they might be.  Also, avoid confusion at your facility by using clear language.  State concentration specifically as "weight percent NaOH" or "volume percent product XYZ" or "molarity" or "normal"; just anything but "% caustic"!

------------------------------
Cullen Dwyer
Brewer/Cellar/QA
Finestkind Brewing
Westminster MA
(978) 874-9965x1160
Brewer/Cellar/QAFinestkind BrewingFinestkind BrewingBrewer/Cellar/QABrewer/Cellar/QA
------------------------------


Original Message:
Sent: 06-04-2024 13:37
From: Dirk Loeffler
Subject: Comparing Caustic from different Vendors

When comparing chemicals, there are a few things to watch out for.  Chemical vendors will give recommended use concentrations generally in one of two ways.  Either as percentage active ingredient (e.g. 2% NaOH) or in percent by weight or volume (% v/v or w/w).  Percent by weight is generally only used when using solid products since it is difficult to measure solids in volume and water has a set weight of 8.33 lbs/Gallon.  Caustic as a concentrate is given in percent by weight or as percent active NaOH.  The solubility limit of Sodium Hydroxide is just above 50%, as you already correctly stated.  There is no 60% NaOH in liquid form.  There are 98% flakes or beads, but these are solid products.

You can measure Sodium Hydroxide strength by density; however, this would assume that the product is pure Sodium Hydroxide without any additional compounds added.  Your NaOH titration is in fact the best way to determine the concentrate strength of your caustic cleaner.

A table with conversion of active NaOH to specific gravity can be found here:

www.handymath.com/cgi-bin/naohtble3.cgi?submit=Entry

What you are looking at here is your basic chelated caustic CIP cleaner, which is not very cost effective. These products are generally used at concentrations between 2 - 5% NaOH in order to be effective.  At 42% active NaOH, this would translate to 4.8 - 11.9% by volume.  In comparison, a modern built CIP product like those sold by us is used at concentrations between 1 - 3% by volume.

I am assuming that this is a liquid product. If so, there is no possible way for the product to be above 50% active NaOH.  Concentrations above 50% are only possible with solid products.

I hope this helps and please send me an e-mail if you want some information about brewery specific CIP products.  My contact info is in my signature.      

Cheers,

------------------------------
Dirk Loeffler
Exec. VP of Technical Operations
SEKA Chemicals, LLC
loeffler.dirk@sekachemicals.com

No reason to doubt your titration. Lots of reason to doubt your vendor. The solubility limit for NaOH is around 50% w/w at 25 C. That is ample reason to doubt the 60% w/w solution. Solubility gets lower at the temperature increases. 98% NaOH would be a solid with a little sodium carbonate and moisture. You do not want to deal with 98% NaOH. It releases lots of heat when you add it to water (don't add water to chemical, add chemical to water).

Roger Barth, PhD
Professor Emeritus of Chemistry
West Chester University
rbarth@wcupa.edu

Author of
The Chemistry of Beer, The Science in the Suds, Second Edition. ISBN 978-1-119-78333-0
Mastering Brewing Science: Quality and Production. ISBN 978-1-119-45605-6.

________________________________

This e-mail message was sent from a retired or emeritus status employee of West Chester University.