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Topic: determining concentration of caustic soda in solution.  (Read 5212 times)

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Offline Morphic flip

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determining concentration of caustic soda in solution.
« on: January 26, 2018, 03:14:06 PM »
What would be the easiest way of determining the concentration of caustic soda in a solution that also contains sulphated castor oil? Both are low concentrations.
Any help appreciated.
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Offline chenbeier

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Re: determining concentration of caustic soda in solution.
« Reply #1 on: January 26, 2018, 05:58:17 PM »
Using a pH-probe and a titration.
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Offline Morphic flip

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Re: determining concentration of caustic soda in solution.
« Reply #2 on: January 27, 2018, 02:36:01 PM »
titration against what strength HCl?
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Offline chenbeier

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Re: determining concentration of caustic soda in solution.
« Reply #3 on: January 27, 2018, 09:07:36 PM »
You have to check to use 1 m or 0,1 m HCl.
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Offline Arkcon

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Re: determining concentration of caustic soda in solution.
« Reply #4 on: January 28, 2018, 06:21:34 AM »
You can check a pharmacopeia, if it specifies how to determine adulterants in sulfated castor oil.  You'll be required to do that, if you expect to sell this castor oil, as a pharmaceutical.   There may also be ASTM testing protocols available.   A purchaser may expect you to follow such testing protocols, especially if you claim to be doing so.

Quote from: chenbeier on January 27, 2018, 09:07:36 PM
You have to check to use 1 m or 0,1 m HCl.

If you're just curious, you can design a titration on your own, as was described here.  You start with a balanced reaction.  You make a guess as to how much caustic there is.  You consider how big of a sample you can handle, and determine which concentration will keep the reaction volume reasonable.  You can test that it works, by spiking some caustic into water.  And again, by spiking some into some sulfated castor oil that you know is clean.  You can also test your precision.
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Offline Morphic flip

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Re: determining concentration of caustic soda in solution.
« Reply #5 on: January 28, 2018, 08:57:54 AM »
OK, thanks.

So if it takes say 25ml of 0.1M of HCl to neutralise 50ml of the caustic solution, the equation would be

25.00 ml x 0.1M / 50.00 ml

=0.05M ?

What would 0.05M be as a percentage in 100 litres of the caustic solution?

Thanks, but I'm new to this.

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Offline chenbeier

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Re: determining concentration of caustic soda in solution.
« Reply #6 on: January 29, 2018, 04:12:42 AM »
What does 0,05 M means? Please express in a different unit. If you know that change this to mass value. Then you need the specific gravity of the solution. The ratio of your result devided to the mass of the solution will guide you to the percentage.
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Offline Morphic flip

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Re: determining concentration of caustic soda in solution.
« Reply #7 on: January 29, 2018, 11:15:19 AM »
0.05M is molar strength result.
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Offline chenbeier

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Re: determining concentration of caustic soda in solution.
« Reply #8 on: January 30, 2018, 06:59:33 AM »
No I mean what can you write instead of M. Which unit?
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Offline Morphic flip

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Re: determining concentration of caustic soda in solution.
« Reply #9 on: January 30, 2018, 01:51:15 PM »
do you mean grams?
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Offline chenbeier

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Re: determining concentration of caustic soda in solution.
« Reply #10 on: January 31, 2018, 04:32:40 AM »
You have to calculate to the mass (gram),

But it doesnt answer what M is in a correct unit.
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Offline Morphic flip

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Re: determining concentration of caustic soda in solution.
« Reply #11 on: January 31, 2018, 12:09:39 PM »
What are the equations to do so please?
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Offline Borek

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Re: determining concentration of caustic soda in solution.
« Reply #12 on: January 31, 2018, 01:53:37 PM »
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Offline chenbeier

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Re: determining concentration of caustic soda in solution.
« Reply #13 on: February 01, 2018, 02:17:58 AM »
Quote from: Morphic flip on January 31, 2018, 12:09:39 PM
What are the equations to do so please?

M = mol/l convert to g/l  convert to g/kg convert to %
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Offline Morphic flip

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Re: determining concentration of caustic soda in solution.
« Reply #14 on: February 02, 2018, 02:33:44 PM »
OK, thanks. I'll have a go, but never been any good with formula's
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