Chemical scientist needed

[Odsox]

I have a technical chemical question that someone here might be able to answer.

Every now and again we have to get our water from a deep borehole (when the spring water slows down)
Now I know that it is full of minerals, but I don't know precisely what minerals they are.
But one thing I have noticed .... I have fruit for my breakfast with cereal and this week the fruit is blackcurrants.
When I soak the dish, the blackcurrant juice turns the water a nice purple shade (as you would expect), but later I notice that the colour has changed to a bright blue.
I've noticed this before with other purple fruit like blackberries.

So, any idea what chemical substance would do that ... a bit like litmus paper ?

[mrsflibble]

the fact that your blackcurrants changed colour is because something in your water is off balance. blackcurrants are a purple berry, which means they contain pigment from a group called anthocyanins. anthocyanins react violently to ph changes.

they went from purple to blue? well the way to test it would be take a squished blackcurrant and add lemon juice. what colour does it go? take another squished berry and add a solution of bicarbonate of soda... again, note the colour. whichever one goes within the same colour range as your currants went this morning is the basic solution you have in your water, be it acid or alkali. i hope you're still with me on this!!!

for instance, red cabbage water. red cabbage contains an anthocyanin called flavin. it goes bright pink when applied to acid, and bright green when applied to alkali. anything pink-purple is acidic, anything purple-green is alkaline.

hope this helps, you will at leats know which scale your water is on lol!!

[Cloud]

I think I've read some place that purple blackcurrent juice is made blue in an alkaline solution. So It does suggest you have a natural 'litmus' and your water is mildly alkaline.

[Odsox]

Thanks for that.
I have just tested the well water and it has a pH of 6.6
I know the spring water is pH 7.6 and as we use that water for 98% of the time explains why it's immediately obvious when that happens.

Not sure I like the idea of eating anthocyanins for breakfast though

[wolfsong]

Blackcurrant colouration seems to be caused by Anthocyanins, which are a pretty standard purple colouration, occurring in everything from blood oranges to violets... under different pH (acidity levels) they can become blue, just digging out a test I think contained something about this exact reaction...
I'll be able to confirm this tommorrow, but i seem to remember, yes... it is the same chemical... Anthocyanins turn Blue at a pH of 8.5: your water is quite alkaline, normally its around 7, or 6.

hang on, 6.6 doesn't sound too bad, is it still turning it blue?

[Shirley]

same happens here and our water is slightly alkaline - can't remember whether it did it when the water was acidic though.

[Cloud]

A ph of 6.6 is on the acidic side of neutral. What else was in the water when soaking. Could that have made the water more alkaline?

[wolfsong]

detergents often contain pH modifiers, or heavy rainwater could have put excess lime into the well, it all depends, but 6.6 should be nothing to be worried about... Carry on as you were!
Another of nature's quirks...

[Odsox]

A ph of 6.6 is on the acidic side of neutral. What else was in the water when soaking. Could that have made the water more alkaline?

Nope, just pure tap water .... just filled up my cereal bowl to stop it drying on, not to wash it.

I just tested it again with another completely different solution and this one came out at pH 6.4, so not an error on my first test.

The reason I asked about "minerals" is because the mountains where my water comes from contain copper, silver and lead amongst other things and the route from there to here is all moorland .. no agriculture at all.

[wolfsong]

hmmm... lots of lovely metals... might be worth having a test done, just out of interest as to what's going on in there.
does the taste vary a lot? because I'm pretty sure about it Anthocyanins changing at pH=8.5

[Odsox]

hmmm... lots of lovely metals...

Yeah, I forgot there is tin as well. I have several rocks embedded with tin crystals in my dry stone wall ... amazing things to look at.

The water tastes pretty disgusting compared to the spring water, just like Vichy water, very minerally.
I have only had it tested a few time for faecal coliforms, but as we only use it during drought conditions it's not worth the bother really.
This year so far it's been on for 3 days and the last 2 years not at all.

[wolfsong]

hehe, we're on clay and limestone, the most boring stuff you can get... apart from finding sharks teeth in your courtyard every know and again .
Anyways, hope we solved your problem, its probably the mineral salts dissolved in the water reacting with the pigment... at least i've finally found a use for all the silly organic chemistry i've had to do... and now: REVISION!!! (A-levels next week )

[wolfsong]

Right, have just checked that paper I quoted, I got the colour wrong, it goes Green at 8.5, blue is pH=6, which sounds more coherent with your observation.
Sorry about that but its funny anyway!