Are silica crystals the things that are in those little plastic dehumidifiers?

[lucysmam]

I need some for an activity for my Guides, as cheaply as possible but am not sure whether the things in those little damp traps are what I need.

Quick bump, hopefully someone will know so I can either pick up a couple on my next trip to town or order silica crystals online :)

Googling them it appears that most are filled with calcium chloride.

Hmmm, I have no idea what that is (and didn't think to Google )

Thanks @JellyBeanScene :)

You can getsylica crystals cat litter

Ooh, that might be cheaper than the little tubs I saw on ebay. Thanks @MrsJayy, I'll look on Tesco before I order my shop.

Trouble is they lose their dehydration powers pretty quickly if exposed to air for prolonged periods. What's it for?

Thats ok I only know that because it is what i used to collect a urine sample when we had a cat.

@bellinisurge to mix with bicarb & (eventually) vinegar to create a reaction. It's for a CSI meeting.

I think silica cat litter would be an option. Can be pricey though

Online tesco doesn't tell me what's in the ones I've clicked so far (the only one that's obvious is the one that says "wood"!) I need to get dd2 tucked up then I'll go through the others.

I think the silica ones are branded "Bob Martin " although I think there are supermarket "own brand " ones.

You can get refill bags of calcium chloride granules in Wilkos.

Why do you want those to add to the vinegar and bicarb mixture - all they do is absorb water and turn into liquid themselves (don't ever try to vacuum them up after a spillage, you'll have liquid dripping out of your vacuum for ages!)

Vinegar and bicarb do an impressive explosion by themselves.

I used to buy the gel cat litter, was in a pale blue pack I think.

I need enough "samples" for 4 groups to use towards working out whodunnit from a possible five suspects @Butterchunks. That's what the instructions say to use.

A tsp of the bicarb/crystals, in an ice cube tray, mixed with A drop of vinegar from a pipette (just to make it fizz). I need three to fizz, as evidence that the suspect has stood in spilled cleaning product. And two not to fizz so the finger doesn't point to them.

I'm definitely open to other ways of doing it!

That sounds very cool, I've got a PhD in chemistry so am really pleased to hear about tasks like this for groups of girls! Do you have a link to your instructions or a photo? The reason I ask is that if you use silica gel (like the little packets you sometimes get in handbags, clothes, pregnancy tests etc) it won't react with the mild acid and water solution of the vinegar, you might hear some cracking noises but it's harmless (obviously not to be eaten or rubbed in eyes, hands washed etc afterward).

However I would strongly suggest not to use calcium chloride for this experiment with the Guides, it would not be safe! I've just done a quick online search of the hazards associated with calcium chloride by looking up the materials safety data sheets (MSDS) and it can cause injury to skin, eyes and internal injuries if inhaled/consumed. You can see for yourself by googling "calcium chloride safety" can't do clicky links on my phone sorry. So it's nasty stuff if not handled with care and you definitely don't want to take any risks around young people.

May I also suggest that you get some safety glasses for your Guides to wear, they don't have to be expensive (packs of 12 are less than £20 on Amazon). Any good young scientist should look after their own safety especially if you're doing tests that might fizz or bubble

Forgot to tag you...@lucysmum

Try again...@lucysmam

@Butterchunks I have the document saved on my phone but not sure how I'd attach it here. Ooh, unless I screenshot the relevant page!

We have safety glasses already in the cupboard at our hall - we tried glass engraving last year & I didn't want dust in eyes so invested in some pairs and was given others (and dust masks too!).

I'll screen shot the page and pop it up

Would the inside of a nappy work too?

It's for the shoe scrapings part - first picture is the activity, second is the resource info :)

@lucysmam that looks like so much fun, loving the pen chromatography too. As someone's already suggested you could get some cat litter silica crystals, if they're safe enough for cats to wee on then a bit of vinegar should be fine too. If you need your samples to have the same texture for the scrapings you might need to crush the cat litter to match the bicarb, I'd suggest doing this somewhere ventilated and with dusk mask. Alternatively you could use flour or crushed salt.

I'm very jealous of your Guides - glass engraving! I think the most exciting think we did at guides (20 years ago) was sticking tea lights in shoe boxes and "cooking" bacon over the candles...this was me later that evening (not envy).

Good luck with it all, I hope you and your girls have a great time.

So... it's a need for something that looks like bicarb and won't react with vinegar?

Icing sugar?
Or something acidic, like cream of tartar or citric acid (for descaling kettles)

@Butterchunks and @BringOnTheScience I think we'll use flour or icing sugar - I have plenty in the cupboard that a few spoons won't be missed!

Butterchunks we try to do all sorts of things with the girls; the last two weeks have been basic sewing. This week we're engineering geodesic domes using spaghetti and marshmallows then going to test their strength :)

Sounds great fun.

Why don't they have clubs for old gimmers like me so we can do these activities?

@palominoo The Trefoil Guild is the adult bit of Guiding, although many of them are 'retired' leaders so very much older. There's a new form of The Senior Section in development aimed at 18-30.