Science geek soap question

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Science geek soap question

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Jb

Joined: 08 Jun 2005
Posts: 7761
Location: 91ï¿½ N

Posted: Fri Jun 19, 20 10:26 am Post subject: Science geek soap question

Doing some home education with my son and one of our current topics is soaps and oils.

So maggie and Alistair were looking at emulsifiers and miscibility in the kitchen while I was making models of hydrophilic / hydrophobic molecules and comparing them to what we saw in practice. One of the side branches I was playing with was soap making. Most of the recipes I've seen want Sodium hydroxide, sodium chloride and a vegetable or animal fat. All of that I have to hand. I also have seen recipes including Calcium nitrate but haven't found why.

So ... what is the purpose of adding calcium nitrate to soap?

(without being too boastful our home curriculum is a damn sight more interesting than the regular key stage 2 science!)

dpack

Joined: 02 Jul 2005
Posts: 46188
Location: yes

Posted: Fri Jun 19, 20 12:50 pm Post subject:
no idea about that but if you do make soap , be careful, caustic is nasty, normal lab rules apply iirc it often needs maturing before it is ready loads of fun to do.

dpack

Joined: 02 Jul 2005
Posts: 46188
Location: yes

Posted: Fri Jun 19, 20 12:58 pm Post subject:
ps ace oppertunity to learn about ppe and handling skills for a reasonably horrid chemical. you will need accurate scales, amounts matter if you want soap that does not remove skin. get that right a few times and then look at but do not make detergents at home diy suplhonations are not wise

tahir

Joined: 28 Oct 2004
Posts: 45665
Location: Essex

Posted: Fri Jun 19, 20 2:51 pm Post subject:
Talking soap this is interesting: https://www.bbc.co.uk/news/science-environment-53081194

Slim

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Fri Jun 19, 20 5:46 pm Post subject:
Good idea to keep a bottle of vinegar handy when dealing with lye (but follow with lots of water if use is needed)

dpack

Joined: 02 Jul 2005
Posts: 46188
Location: yes

Posted: Fri Jun 19, 20 6:15 pm Post subject:

i prefer gloves, goggles and lab coat(improvise is fine if it seems practical)for small amounts and full acid suit if 20000 litres of saturated are involved even if they are tank to tank by pipe

if you are dissolving it into water and/or fats in a bowl tis best to have a decent breeze, mask or fume cupboard.

the aerosol it can make is not nice to breathe or look through for a short while

drown out used kit in water before you clean it

etc

a spec of crystal or flake on the skin can be not noticed until you have a nasty lesion, in solution it has the potential to be well messy especially in the eyes

although it is "domestic" it is really quite nasty to work with, i prefer "acid reactions", "on fire or potentially bangy", "high pressure" and "toxic stuff" to using caustic with basic ppe and domestic science protocols

a small mistake is potentially life changing, unlikely to die
big mistake can be fatal

cat 3 risk imho but please be careful and sensible.

advice from an old, almost undamaged/or damaging chemist, a few near misses though:wink:

Mistress Rose

Joined: 21 Jul 2011
Posts: 15949

Posted: Sat Jun 20, 20 7:42 am Post subject:

I would agree about safety precautions. An alternative that might be fun to make is lye water using wood ash. It won't be quite as potent, but care still needs to be taken, but as it is being concentrated rather than diluted, less chance of accident.

First you will need a lot of fresh wood ash. Bonfire or wood fire ash is good, but it must have been kept dry. Add water and stir, then allow to settle for at least a couple of hours. Either filter (another useful technique to learn) or decant the liquid. It then needs to be concentrated by boiling or allowing to evaporate with time until an egg will just show a piece the size of a 10p piece when floating in it. Use that as the lye, but you will need the sodium chloride to make solid soap.

You don't need sodium chloride if you are using sodium hydroxide, but you do need to let it stand for several months as the lye takes a long time to fully react with the fat.

Mistress Rose

Joined: 21 Jul 2011
Posts: 15949

Posted: Wed Jun 24, 20 7:18 am Post subject:

Another science experiment your children may like is chromatography. You will need either some blotting paper, coffee filters, or some other fairly absorbent paper that won't fall apart and some water washable felt tip pens.

Draw a line with one colour pen on the paper, then hang or hold it, so that the line is parallel to and just above a bowl of water. As the water rises up the paper, the ink will split into the different colours used to make it. The best one is black as I remember as that contains a good range, but some others are pretty interesting too. Should keep them occupied for some time, and you can explain the theory behind it to them to make it educational.

buzzy

Joined: 04 Jan 2011
Posts: 3708
Location: In a small wood on the edge of the Huntingdonshire Wolds

Posted: Wed Jun 24, 20 9:25 am Post subject:

MR, we did this in chemistry at school. We used a chemical filter paper. We cut a radial line a couple of millimetres wide from centre to edge so the strip dangled down. Put the drop of ink being tested at the centre where the strip begins, and support the paper over a suitable sized beaker with water in the bottom so the tip of the strip dips in it. Water rises up the thin strip and makes a nice fancy ring effect of colours depending, as you say, on how the original ink is composed. I think we were just showing that that black ink was not a pure black, but I suppose you could put two or more dots of coloured ink and get the designs of your choice. Hope I have explained this method well enough!

Henry

dpack

Joined: 02 Jul 2005
Posts: 46188
Location: yes

Posted: Wed Jun 24, 20 11:32 am Post subject:

Mistress Rose wrote:

i have done it professionally by assorted means, kitchen/garden science is very easy and educational with basic kit and skills.

plant material
grind it with a bit of sand, extract the juices with a splash of vodka, spot it (maybe a few times letting it dry between coats, run in a tank of mixed solvents(surgical spirit and nail varnish remover might be an option)

water based felt tip pen dye mixes and inks in general run ok in plain water on blotting paper or similar, the substrate should have a unidirectional or very directional nature

jam jar will do for small bits but a "tank" to ensure minimal evaporation is useful for decent seperations

have you got a low power ie safe uv torch?
that can be loads of fun with chromatographs, nowt to see at all until you light it up

or chemical"developer" to bind with and show up the things you have seperated

in a while i could guide you through "build your own GLC", that is loads of fun and i guess a raspberry would substitute for a bbc/D in the control gear with little bother

another fun analysis thing, titrations are very educational if used well, learn loads about chemistry and maths* from titrations
again some basic kitchen kit and maybe a dosing syringe would be adequate kit at a push.
there are many plant pigments that will indicate Ph for instance

*STEM is a package:wink:

Mistress Rose

Joined: 21 Jul 2011
Posts: 15949

Posted: Thu Jun 25, 20 7:05 am Post subject:

Henry, I have a vague idea I did do something like that with a coffee filter to get the rings, but it was over 30 years ago, so can't really remember.

The first gas chromatograph I came across was a very Heath Robinson affair at college. That sort of thing was just coming in, and one of the lecturers built this amazing 'thing' at the back of one of the labs out of miles of glass tubing. We tried it, and after about an hour, nothing had come through, so we gave up, as even the inventor of the device agreed that it hadn't worked.

As you say, a very basic titration idea using a liquid from plants (I understand red cabbage water works quite well if you have it) as an indicator might be quite educational.

dpack

Joined: 02 Jul 2005
Posts: 46188
Location: yes

Posted: Thu Jun 25, 20 10:28 am Post subject:

the first glc i used was mostly made out of old radar parts by the chap who was the technician on developing uk radar capability with mr famous:lol:

i made one for fun and example as a school tech, worked pretty well even if i was using washing powder as the filtration media in the tube and the detector was made out of a thistle funnel with a few "wires" and had a domestic gas flame jet as improvised glass blowing

a very basic pooter is ideal for control gear

hplc is really fun

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