# How can I weigh liquid in a sealed container?

How do you measure the mass and volume of alcohol if it is in a sealed container? Are there clever ways of achieving this?

The weight of the container is not known. I can't open the container, I can't lose the alcohol inside, and I can't immerse it in water (as the label will break).

• Is the alcohol in the container pure, or is it a mixture of some concentration (e.g. a drink)? If it's a mixture, do you know the concentration? If you do it's not hard to estimate, but if not I think it's very difficult, if not impossible, without knowing the weight of the container. Commented Oct 2, 2013 at 7:08
• Is the container full? Commented Oct 3, 2013 at 4:04
• The container is not full. It is a wine bottle so it isn't pure alcohol and the concentration is unknown. The weight of container is unknown (every bottle is different).
– ytk
Commented Oct 3, 2013 at 5:54
• I appear not to have an reputation here--odd. Anyway, if someone would like to repost this as an answer: given that the bottle's opaque, there really is no practical way to evaluate the contents' water-alcohol ratio. I'd be tempted to run a microfine syringe needle thru the cork and draw a sample. However, your best bet in the "real world" is to ask some oenophile club, not physicists. Commented Nov 12, 2013 at 16:25

You send the box and liquid towards a barrier equipped with a gauge to measure force. The setup looks like:

When the box hits the barrier it stops, but the liquid inside it keeps moving. A short time later the liquid hits the side of the box and it too stops moving. So when you record the force at the barrier as a function of time you will get two peaks, first as the box hits the barrier and stops, then a short time later a second peak as the water hits the end of the box and stops.

If you integrate the force time curve you will get the impulse during the collision, and this is equal to the change of momentum. Since momentum is $mv$, and you know the velocity $v$, you can calculate the mass. The two peaks will give you the mass of the box and the mass of the liquid.

Needless to say, in real life you will get only approximate results. The peak for the box should be clear, however the viscosity of the liquid will mean there is a force exerted on the barrier while the liquid is moving and before it hits the end of the box. Also the liquid will splash, so the impulse you measure will be too high. However the method should give you an approximate result.

• It's a bottle of wine made of ceramics and it is a very old bottle. I'm a little worried of using this method to be honest. But let me think if there is a gentle way to apply it. Thanks :)
– ytk
Commented Oct 3, 2013 at 5:04
• "The peak for the box should be clear"-calculate the mass of the box and subtract that from total mass Commented Oct 4, 2013 at 6:04

ytk. If you rolled the bottle down a inclined plane then you can estimate the volume inside by noticing the time difference between by a full bottle and semi filled bottle or empty bottle:( or whatever filled since their different moments of inertia. Take viscosity effects for honey:) I leave calculations for some competent person to do or do it for your self.

Bonus lesson. You can roll a full bottle and semi full bottle on a table and the curvature towards the head of bottle will be more for semi filled.

I am sorry for posting this as an answer, as it might be more appropriate as a comment. I just signed up in Physics and can't write comments yet...

This is an really intriguing question, and although I have some ideas although not a solution.

• Heat - Warming the container you could measure how fast the heat spreads and maybe even the pattern with an optic thermometer (or how are they called). This approach would give you the volume of the liquid, as you could see how much of the container heats up. Different substances have different heat capacities and if the liquid largely consists of water and alcohol (disregarding everything else) you could probably find out the mixture, especially if you have a second variable such as the change of momentum or density mentioned above.

• Density - Even if you don't want to soak the labels, you can just wrap plastics or this latex film used for so much in the labs. But I'm not sure what useful information you can get from this, just mentioning it if someone else has an idea building on it.

But I doubt how useful any of these methods are. Once you got the density/mass/viscosity of the liquid you still don't know exactly what it is, as it's composed of a mixture of a large amount of different substances, assuming it is old containers with wine or any other drinkable liquid.

How is the lid/cork? Would it be possible to insert a needle and take a sample of the liquid itself? Then you could run it through more standard procedures like a photospectrometer or however professionals would treat it...