Got a bottle of unknown red solution

[Elite Engineer]

I got a crate of chemicals from my neighbor, most were unlabeled. I found glass bottle of a red liquid. I mixed it with sodium hydroxide, and the solution bubled and turned

 

yellow. Me thinks this is probably methyl red or some kind of pH indicator. Thoughts?

 

~EE

[Function]

Thoughts? Don't drink it.

[Sensei]

I got a crate of chemicals from my neighbor, most were unlabeled. I found glass bottle of a red liquid. I mixed it with sodium hydroxide, and the solution bubled and turned yellow. Me thinks this is probably methyl red or some kind of pH indicator. Thoughts?

 

If it releases gas during reaction, you should measure precise mass of either compound, and put graduated cylinder above it, to catch gas and measure its volume.

1 L = ~ 0.04464 mol at room temperature or so. So you will know how much mass/moles of NaOH gave which volume of gas in result.

 

Then check out which gas it is.

If it's Hydrogen, fire will cause explosion.

If it's Oxygen, fire should be more intense.

If it's non-flammable gas, such as Carbon Dioxide or Nitrogen, fire should disappear.

 

According to Internet methyl red is red solid, not (or barely) soluble in water, and soluble in ethanol.

[Elite Engineer]

 

If it releases gas during reaction, you should measure precise mass of either compound, and put graduated cylinder above it, to catch gas and measure its volume.

1 L = ~ 0.04464 mol at room temperature or so. So you will know how much mass/moles of NaOH gave which volume of gas in result.

 

Then check out which gas it is.

If it's Hydrogen, fire will cause explosion.

If it's Oxygen, fire should be more intense.

If it's non-flammable gas, such as Carbon Dioxide or Nitrogen, fire should disappear.

 

According to Internet methyl red is red solid, not (or barely) soluble in water, and soluble in ethanol.

I'm thinking its a methyl red and ethanol solution. The guy seemed to have alot of indicator stuff. Not sure how I'd measure the gas volume. I'll post pictures tomorrow.

[John Cuthber]

Measuring gas density is very difficult.

Measuring the density of the liquid will give you a clue about the solvent.

 

It's also possible that the gas that's released was dissolved air, rather than anything produced chemically.

[Sensei]

Measuring gas density is very difficult.

Then why do you introduce it?

Nobody mentioned measuring gas density, prior you.

I said only about measuring gas volume, in graduated cylinder..

 

Measuring the density of the liquid will give you a clue about the solvent.

 

Not really, if you don't know concentration.

f.e. ethanol mixed with water has density between 0.789 g/cm³ to 1.0 g/cm³

If it's 100% ethanol, 0% water, density is 0.789 g/cm³,

If it's 0% ethanol, 100% water, density is 1 g/cm³.

If there are used both, density is somewhere in between them.

(let's pretend air pressure doesn't matter)

Edited June 8, 2016 by Sensei

[Greg H.]

"I got a bunch of unlabeled chemicals from my neighbor." sounds like the beginning of a story that will involve the phrase "Hey y'all watch this!" at some point.

 

Why don't you ask your neighbor what it is?

[Elite Engineer]

"I got a bunch of unlabeled chemicals from my neighbor." sounds like the beginning of a story that will involve the phrase "Hey y'all watch this!" at some point.

 

Why don't you ask your neighbor what it is?

His uncle was a chemist at DuPont, and he gave him the chemicals (not sure why). He passed away years ago, and he gave me the chemicals when he said he was going to toss them.

[John Cuthber]

Then why do you introduce it?

Nobody mentioned measuring gas density, prior you.

I said only about measuring gas volume, in graduated cylinder..

 

 

Not really, if you don't know concentration.

f.e. ethanol mixed with water has density between 0.789 g/cm³ to 1.0 g/cm³

If it's 100% ethanol, 0% water, density is 0.789 g/cm³,

If it's 0% ethanol, 100% water, density is 1 g/cm³.

If there are used both, density is somewhere in between them.

(let's pretend air pressure doesn't matter)

OK, you didn't introduce gas density- you introduced measuring the mass and volume of a gas.

"If it releases gas during reaction, you should measure precise mass of either compound,"

 

And if it's an indicator solution then it's almost certainly pretty dilute.

If the density is near 0.789 then it's probably a solution in alcohol.

If the density is near 1 it's probably a solution in water.

Did you not realise that?

And we can probably pretend quite well that pressure doesn't matter- nobody involved here will be measuring a liquid's density accurately enough for changes in atmospheric pressure to matter much.

 

As I said, I'm not sure that the gas release is a chemical reaction anyway.

 

There aren't many candidates for "stuff that, after sitting in a (glass?) bottle for ages suddenly releases a gas when treated with NaOH.

Can you think of any plausible ones?

[Sensei]

There aren't many candidates for "stuff that, after sitting in a (glass?) bottle for ages suddenly releases a gas when treated with NaOH.

Can you think of any plausible ones?

 

If somebody would have NaOH placed in container that is not hermetic, NaOH+CO₂ (from air, for months/years) -> NaHCO₃ and Na₂CO₃

After adding almost any stronger acid will release CO₂ gas bubbles.

 

From my wikipedia of Sodium Hydroxide, Google translated:

"The solid white substance of the crystal structure . It is hygroscopic , easily also combines with carbon dioxide from the air ( forming a coating of sodium carbonate ), so it should be kept in tightly closed containers ."

 

(there would be needed also some red acid to mimics OP observations).

 

ps. I do agree that it's most likely indicator, from what EE described.

Edited June 9, 2016 by Sensei

[John Cuthber]

Yes, I thought about that but, if it's true then measuring the volume of gas isn't going to get you anywhere in identifying the red stuff- i.e. what tEE was after. I don't see a reason to assume that he left the reagent lying round for ages.

Also, the liquid changed colour- that suggests an excess of NaOH was added.

CO2 would be trapped as carbonate or bicarbonate by excess NaOH..

[Elite Engineer]

I uploaded some pictures of the "unknown red liquid" along with it reacting with some lye. As you can see the reaction created a yellow product. pH indicator most likely?...methyl red?

 

 

 

 

[John Cuthber]

Just for the record, adding unknown chemicals to very strong bases like NaOH is a dangerous game to play.

[Elite Engineer]

Just for the record, adding unknown chemicals to very strong bases like NaOH is a dangerous game to play.

I did it outside, with full lab attire (goggles, coat, gloves) and in very small quantities. What other way is there to see if solution A is acidic or not?

[John Cuthber]

I did it outside, with full lab attire (goggles, coat, gloves) and in very small quantities. What other way is there to see if solution A is acidic or not?

Have you heard of litmus paper, or a pH probe.

But that's beside the point. If the stuff was a solution of eosin in dilute acid, adding a base wouldn't have changed the colour.

 

Also, using a very concentrated alkali would sometimes give misleading results. For example, the heat of reaction with water might boil some volatile solvent off, giving the false impression of gas release.

Such a strong alkali wouldn't, for example, make phenolphthalien turn pink.

So you exposed yourself to a smal, but unnecessary risk for nothing.