What chemical would dissolve in air, but not liquid?

[Anagoge]

I'm not sure if this is in the right forum so apologies if it isn't.

 

I'm looking for two things. Firstly, some form of edible chemical or material treated with a chemical that would either turn translucent/transparent or break up when exposed to air, but be visible and cohesive when in an acidic liquid (i.e. fruit juice).

 

Secondly, I'm looking for something that does the opposite of the above. Something that is translucent/transparent in liquid, but when exposed to air becomes visible. If these two things happen to be the same chemical, that would be great, but it's just as useful if they happen to be two separate things.

 

The chemical and/or material must be edible as it would be in contact with juice that people would be drinking.

 

I'm in no way knowledgeable about chemistry so a simple explanation would be very much appreciated! Additionally, if you know of somewhere where I could read up further on such a chemical/material that would be great, as it'd back up my research.

 

Many thanks for your help.

Neil Martin

[hermanntrude]

tell me more about what you plan to do with this chemical... I think i can see what you're getting at but i'm not totally sure

[Anagoge]

I'm a graphic designer doing a project surrounding fruit smoothie advertising. The concept is to fill a poster-sized clear container with actual smoothie which then dispenses a sample to the public. On the inside of the container would be typography/visuals stuck to the front wall of it. As the container empties, the typography/visuals would disappear and would be replaced with different visuals on the back wall of the container. So, there would be one message while the container is full and another when it's empty and both of these messages would depend on how much of the smoothie had been dispensed.

 

I hope that helps.

[hermanntrude]

hmm so you're basically looking for a solid-state acid-base indicator that's non-toxic.

 

perhaps this might help?

 

many flowers and fruit contain substances which change colour in the presence/absence of acid. The trick would probably be in making it stay on the glass rather than dissolve into the juice.

[Anagoge]

Thank you for the help. That link is quite useful. However, according to that, the indicator would only turn a different colour. Is there anything that would become transparent instead? For example, just imagine that while in the presence of acid, the message said "ON", but in the absence, "OFF" - It would be confusing to see both "ON" and "OFF" and one of them would need to be hidden/clear/dissolved. Basically not visible. Any suggestions?

 

Edit: One more thing that may be useful to know is that once this chemical/material has been exposed to air and no longer visible (after being submerged in fruit juice), there isn't any requirement for it to reappear. In other words, as the container empties, it's acceptable that the chemical can lose its activeness because there is no chance of the container being refilled.

Edited March 21, 2009 by Anagoge

[hermanntrude]

I can see two possible ways of dealing with the transparency issue:

 

1) use a material for the container which is the same colour as one of the colours of the indicator

 

2) Use a different indicator which is colourless either at high or low pH

[nitric]

the only substance i could think of that turns colorless( warning, dont use this) is phenolphthalein, buts its cancer causing. try a google search, i bet there are plenty of products you could find for this...

[Kaeroll]

Unrelated to the acid/base issue: how are you going to preserve the smoothie? I'm assuming you're not going to change it daily in every poster you have up. If your smoothies are wonderfully fresh they won't keep too long, surely?