Making up Sodium Hydroxide solution

[SiSandrine]

OK given we have some pretty good chemists on the forum. I am out of Sodium Hydroxide, miles away from nearest home brew shop but close to Boots which sells 98% Sodium Hydroxide (caustic soda). If I add 4.4grams of that to 1 litre of water would that give me N/10 solution? Is 98% purity good enough?

[koomber]

98% Purity will almost certainly be good enough, and it almost guaranteed to be what RITCHIES flog in their kits.

Molecular weight of sodium hydroxide = 39.997g (this is 1N)
Therefore, 3.997g will give 0.1N
However your stuff is 98% pure, so we account for this to get 4.079g to give 0.1N.

This should then be dissolved in water and the mixture made up to 1L.

Unless you have access to a volumetric flask you won't be able to get 100% accuracy. Mind you if your using it for titrations with indicator solution then it will probably be good enough, though you might be better weighing the water (go for 1L of water as the density of a 0.1N sodium hydroxide soln is near as dang it 1).

EDIT: So long as you are pretty accurate with your measurements (decimal points on the scales would be good) you should be okay for most acid measurements. Even with a pH probe.

If you are using it with a Ritchie's kit, are you sure the kit is 0.1N? I've seen different numbers offered on the forum (0.1 and 0.2 being the most common) I was going to do a quick check when I get home tonight to make sure.

[DerekSmith]

Pure sodium hydroxide absorbs water and carbon dioxide from the air like a magnet. If your 'pure' sodium hydroxide pellets look white instead of 'glassy' it means they have absorbed CO2 and will no longer be 98% as it has converted to sodium carbonate/bicarbonate.

If your 'pure' pellets are opalescent, then they are OK, but don't leave the cap off the bottle or leave them in the air while you are weighing them - weigh a little bottle, quickly transfer some pellets into it and seal both bottles quickly, then reweigh the little bottle to see how much you have put in it. Count the pellets and work out how many more / less you need to add to the bottle to get to about 4.1g. The pellets are usually quite large, so it is quite unlikely that you will be able to get exactly 4.1g in the bottle. When you finally know how much you have in your bottle, pro rata the amount of water you weigh out to allow for any under / over weight.

Wt of water needed = wt of sodium hydroxide / 4.1 * 996 g

Derek

[koomber]

I'm going to offer a warning to balance speed with caution. Sodium hydroxide pellets or granules (or indeed flakes) are pretty much pure evil if not handled carefully. You need to make sure you don't loose any of it and for the love of all that is holy WEAR GLOVES. I'm not sure what form boots sell it in but it's pretty much irrelevant.

I have seen water near boil at my work when we make up 25% w/w solutions. If you get a grabule or piece of flake on your hand (or *shudder* under a finger nail) you could be in a world of hurt. This stuff chucks out heat when it gets wet. Not a problem when it is 0.1N since the water will act as a heat sink, but the little pellet or flake on a bare bit of skin...

If you do even suspect you or your work area is contaminated, wash well with PLENTY of water. If you don’t use lots of water you can give it a chance to start to make heat.

Make sure you have an MSDS for it (download one from the net, I doubt boots will have one) and make sure you give it a good read.

Stay Safe!

[mcblades]

This should then be dissolved in water and the mixture made up to 1L.

Unless you have access to a volumetric flask you won't be able to get 100% accuracy.

I tend to weigh my water as well (1g/ml for distilled water at 20C). With a set of reasonable digital scales it's certainly as accurate as a volumetric flask for small volumes and one less thing to break.

cheers

Mark

[DerekSmith]

An alternative to sloshing water around after you have finished, is to lay a large sheet of newspaper over your work surface and have a selotape dispenser to hand. then if a pellet or grain or flake does escape, don't try to pick it up, just patch it in place with a bit of selotape. When you have finished the weighing, bunch up the paper to contain any 'bits' and bin it - any caustic on the surface will quickly absorb moisture from the air and will rot the paper, spending most of its corrosive force safely.

One thing spending 30 years in an analytical lab does is to make you forget that at the start of those 30 years one had considerable training on how to safely and accurately dispense substances. So perhaps the salient advice should be - If you don't think you can quickly weigh out ca 4g of something WITHOUT spilling any, then DON'T try to do it with caustic soda...

If you (or any of your family) do manage to get some on your skin, it will feel quite 'soapy' - this is the caustic rotting your flesh - wash in plenty of cold water first, then, once you are sure you have no concentrated caustic left on you, rub some citric acid solution on the skin to complete the neutralisation (or vinegar as a last resort).

By the way, if a speck of this flies up and gets you in the eye - or falls and gets in a childs, or animals eye - chances are it will have eaten a hole into the eyeball before you have a chance to do anything about it but scream - OK, your wearing goggles, but don't forget, safety is also about being aware of all the others that use the area you are using these chemicals in, until you have made them safe by diluting them to safe levels or locked them away in safe storage.

Let me put this into context for you - I used to analyse meat paste for bone content - a chunk of meat past was dropped into a concentrated caustic bath - there was a quick churning effervescence and 30 seconds later the bone particles would be settling out like white sand to the bottom of the container - the flesh having been totally dissolved by the caustic.

Derek

[koomber]

One thing spending 30 years in an analytical lab does is to make you forget that at the start of those 30 years one had considerable training on how to safely and accurately dispense substances. So perhaps the salient advice should be - If you don't think you can quickly weigh out ca 4g of something WITHOUT spilling any, then DON'T try to do it with caustic soda...

If you (or any of your family) do manage to get some on your skin, it will feel quite 'soapy' - this is the caustic rotting your flesh


Derek

Yup. Caustic is not fun if it goes wrong. I did have fun in a lab once where they were testing cement blocks and part of the procedure involved keeping the blocks submerged in 38°C water. One of the guys couldn't figure out how soap kept getting into the water bath, since if he stuck his finger in it would feel soapy.

Poked a pH probe in the bath and it was about pH 13-14. It wasn't soap in the bath it was the caustic from the cement saponifying the natural oils on his skin

[koomber]

I tend to weigh my water as well (1g/ml for distilled water at 20C). With a set of reasonable digital scales it's certainly as accurate as a volumetric flask for small volumes and one less thing to break.

cheers

Mark

Depends on the chemical and the loading, but broadly speaking your right. For acid calcs in wine any error in weighing/measuring will likely be over shadowed by the assumption that all the acid is tartaric (or sulfuric if you use a ritchies kit).

[SiSandrine]

Thanks for all your advice guys. I intended to prepare the water in a measuring jug (weighed at 1 litre) on my digital scales. I will then add the sodium hydroxide to a ramekin (as the scales have a tare function) and transfer this straight to the water in the measuring jug. The bottle the caustic soda comes in has a narrow neck and is 'pourable'.
What I am going to do with 1 litre of the stuff I don't know as it will have no doubt 'gone off' before I use it all - clean the drains maybe. I like the newspaper / sellotape tip and yes - family will be banned too.

[koomber]

Thanks for all your advice guys. I intended to prepare the water in a measuring jug (weighed at 1 litre) on my digital scales. I will then add the sodium hydroxide to a ramekin (as the scales have a tare function) and transfer this straight to the water in the measuring jug. The bottle the caustic soda comes in has a narrow neck and is 'pourable'.
What I am going to do with 1 litre of the stuff I don't know as it will have no doubt 'gone off' before I use it all - clean the drains maybe. I like the newspaper / sellotape tip and yes - family will be banned too.

Sounds good. If you don't land exactly bang on the desired concentration you can work out the strength of the caustic solution by:

Weight added/40.79 = normality of sodium hydroxide soln.

Then using the info in northernwiners post here:

http://www.winesathome.co.uk/forum/showthread.php?t=4123&highlight=richie+acid+test+kit

you can work out your concentration in tartaric acid

(PS: The point where the indicator soln starts to turn is roughly pH 8.2)

[SiSandrine]

Just on the test then, do you find with reds it is the point that it starts to turn green/grey or the point after that when the pink colour comes. I have seen both suggested and there can be as much as 1ppt difference.

(As I don't yet have a PH meter).

[SiSandrine]

Just thought I'd give a quick update on this as it has been very successful.

So I bought a tub of Boots Caustic Soda (sodium hydroxide) and following (the excellent advice in) this thread I added just over 4 grams to 1 litre (weighed) water.
In order to test this worked I weighed out 4.5kg of water and added 42grams citric acid into that. I mixed / shook well and ensured all dissolved.
I then added 5ml of the citric acid water to a glass jar, 5 drops of phenolpthalein.
Titration showed 6.5ml of my 0.1N NaOH solution needed exactly. So perfect results, I was very pleasantly surprised.
I now have plenty of NaOH solution, a test jar of 42gm/4.5ltr water and high confidence in my titration assembly. Top tip - a jam jar is so much easier than a test tube for titration. It is stable, has a nice wide opening and the wine doesn't squirt out the top if you need to boil the C02 off first.

Thanks for your assistance guys. Next step S02 assembly.

[koomber]

Just thought I'd give a quick update on this as it has been very successful.

So I bought a tub of Boots Caustic Soda (sodium hydroxide) and following (the excellent advice in) this thread I added just over 4 grams to 1 litre (weighed) water.
In order to test this worked I weighed out 4.5kg of water and added 42grams citric acid into that. I mixed / shook well and ensured all dissolved.
I then added 5ml of the citric acid water to a glass jar, 5 drops of phenolpthalein.
Titration showed 6.5ml of my 0.1N NaOH solution needed exactly. So perfect results, I was very pleasantly surprised.
I now have plenty of NaOH solution, a test jar of 42gm/4.5ltr water and high confidence in my titration assembly. Top tip - a jam jar is so much easier than a test tube for titration. It is stable, has a nice wide opening and the wine doesn't squirt out the top if you need to boil the C02 off first.

Thanks for your assistance guys. Next step S02 assembly.

+1 on the Jam Jars. I use an old beer bottle for preference. Easier to grap the top and swirl than using a wide mouthed jam jar.

[parabolic]

Just thought I'd give a quick update on this as it has been very successful.

So I bought a tub of Boots Caustic Soda (sodium hydroxide) and following (the excellent advice in) this thread I added just over 4 grams to 1 litre (weighed) water.
In order to test this worked I weighed out 4.5kg of water and added 42grams citric acid into that. I mixed / shook well and ensured all dissolved.
I then added 5ml of the citric acid water to a glass jar, 5 drops of phenolpthalein.
Titration showed 6.5ml of my 0.1N NaOH solution needed exactly. So perfect results, I was very pleasantly surprised.
I now have plenty of NaOH solution, a test jar of 42gm/4.5ltr water and high confidence in my titration assembly. Top tip - a jam jar is so much easier than a test tube for titration. It is stable, has a nice wide opening and the wine doesn't squirt out the top if you need to boil the C02 off first.

Thanks for your assistance guys. Next step S02 assembly.

so sorry for digging up yet again another old thread , but where do you get that information from about the use of citric acid as a standard for standardising NaOH?

I have only found detailed info on standardising with HCI or KHP, the later being the best method.

I'm just very curious as I'm trying to find a way to sort out my 0.1N NaOH but I never have seen away to do it with citric and can't find the detailed information on it.
I have tried the citric acid method above but my result was way off from 6.5ml which I know could be an indication that my 0.1N is not 0.1N, but I would like to see the numbers on how cirtic acid can be used. If citric acid can be used, that must mean surely that Tartaric acid can be?

[P cuthbert]

Just a quick reminder here. NaOH (sodium hydroxide, lye) is a very caustic substance.

Keep plenty of water to hand or have access to running water. Also, as suggested above, having a neutralizing agent (citric or acetic acid-5% vinegar) is important.

Wear your protective equipment religiously. Nitrile gloves and face shield or chemical goggles are recommended. A chemical apron is advised, and don't forget your footwear. Closed toed shoes, or better, wellingtons.

Your safety when handling chemicals is of the utmost importance. I regularly handle 23% solution, and when doing so, I am wearing a full chemical suit.

Take care and you will be able to enjoy the fruits of your labours.