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Mystery Behind Glass Ampule

09/27/2017 8:20 AM

A lab tube has been placed upside-down in water and (as expected) water does not get into the tube.

In the second image we have a machine sealed empty glass ampoule. A tiny perforation (tenths of a mm) has been made in the sealed area imitating a defective sealing.

I would expect the same to happen as in the first case when placed upside-down in water... but water get´s in!

Why did this happen????

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#1

Re: Mystery Behind Glass Ampule

09/27/2017 8:59 AM

Capillary action.

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#2
In reply to #1

Re: Mystery Behind Glass Ampule

09/27/2017 9:02 AM

Yep.

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#5
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Re: Mystery Behind Glass Ampule

09/27/2017 11:09 AM

I would think that capillary action would draw water into the tiny channel but not into the ampule. The attraction that draws the water into the channel would also act to keep the water in the channel and not let it flow up into the ampule.

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#25
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Re: Mystery Behind Glass Ampule

09/28/2017 9:02 AM

Since the ampule is submerged the capillary action does draw the water into the ampule and normal hydrostatic keeps it there.

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#31
In reply to #5

Re: Mystery Behind Glass Ampule

09/28/2017 9:55 PM

It would depend on the pressure differential between inside the ampoule and ambient. Even if the the delta P is zero, the second you place the ampoule under water, the head pressure will push water into the ampoule.

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#32
In reply to #31

Re: Mystery Behind Glass Ampule

09/29/2017 9:32 AM

Maybe the ampule flattulated. I am just glad there was no twitterpated ampule.

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#3

Re: Mystery Behind Glass Ampule

09/27/2017 10:12 AM

Thank you!

I feel completely embarrased for not having thought in capillarity!

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#4

Re: Mystery Behind Glass Ampule

09/27/2017 10:40 AM

Most snap-cap ampules are sealed under vacuum, this makes them easy to fill with sample (if they are reagent vials for lab spectrophotometry for example), and the other reason for vacuum sealing is to prevent interaction of vial contents with oxygen, etc.

In your case, you broke the seal early, as previously stated by others, it is just capillary pick-up of water in the neck of the vial.

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#10
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Re: Mystery Behind Glass Ampule

09/27/2017 2:54 PM

We purchase the ampoules from Schott Duran, fill them with a volatile product we manufacture (monomer) and seal them with a machine that melts the glass and forms the seal.

Ampoules are inspected 5 times by different crew members and a machine.

Despite this we received a complaint from a Chinese customer saying we sent an empty ampoule. We believe that in this particular case, the seal was not perfect, and that the ampoule may have leaked during air transport due to the reduced pressure in the cargo hold of the plane.

In the pictures we see an empty (on purpose) ampoule in which a tiny puncture has been made on purpose to simulate a defective closure

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#13
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Re: Mystery Behind Glass Ampule

09/27/2017 3:16 PM

that's one out of how many? 1000?,10,000?, 100,000?

Probably better reliability than you thought? Worse than you can tolerate?

Any way to read some part of the spectrum in the liquid head-space of sealed product as a speedy diagnostic? Maybe not...

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#18
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Re: Mystery Behind Glass Ampule

09/27/2017 5:00 PM

So far, our customer only complained about 1 vial. We shipped 5,000 units. No idea if he checked the whole shipment or not.

He believes we are cheating on him, and that the empty ampoule escaped to our controls.

On the other hand, we have nothing to hide (*) and besides minor issues, we never get complaints like this one.

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#28
In reply to #18

Re: Mystery Behind Glass Ampule

09/28/2017 11:25 AM

It is somewhat more than whiny of them to carry on about it.

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#6

Re: Mystery Behind Glass Ampule

09/27/2017 11:56 AM

The water is held at bay by the air pressure in the ampule, the difference is the breadth of the opposition and the resistance to outflow upon removal of the vial....In truth I believe the air in both ampules was compressed equally...

Capillary action would be above the water level, not below...

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#8
In reply to #6

Re: Mystery Behind Glass Ampule

09/27/2017 2:39 PM

When the ampule with the leak was submerged it had enough pressure to overcome the surface tension and viscosity of the water, forcing the water into the ampule....when lifted out of the bath the force on the water was reversed and reduced causing a more gradual expulsion....whereas the open test tube voided immediately....

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#12
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Re: Mystery Behind Glass Ampule

09/27/2017 3:13 PM

This is because the surface tension is the same, but the mass lifted is smaller in the smaller tube.

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#7

Re: Mystery Behind Glass Ampule

09/27/2017 2:17 PM

It seems to me that the capillary action is actually a function of surface tension and geometry. Add a little soap or alcohol and see if it makes a difference.

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#9
In reply to #7

Re: Mystery Behind Glass Ampule

09/27/2017 2:45 PM

Yes, basically the difference in attraction between the liquid and the walls of the capillary versus the attraction for the liquid to itself. This difference can be either positive or negative. When the liquid is more strongly attracted to the walls, the liquid rises. If the liquid is more strongly attracted to itself, the level is depressed.

The height of the liquid displaced is greater in smaller capillaries because the surface to volume ratio is greater in smaller capillaries.

https://physics.stackexchange.com/questions/185686/size-of-a-glass-capillary-for-noticable-capillary-action

The level rise (capillary action) is due to the attraction between the water and the walls of the capillary. This same attraction prevents the water from flowing out of the top.

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#11
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Re: Mystery Behind Glass Ampule

09/27/2017 3:12 PM

In the case of mercury, this fluid is non-wetting toward glass, making it ideal for use in barometric column measurements - of course all those old things have mostly been replaced with pressure sensors of suitable resolution and dynamic range.

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#14

Re: Mystery Behind Glass Ampule

09/27/2017 3:36 PM

Rixter is correct: capillary action would only draw water into the channel.

The reason water has been drawn into the ampule is because the water was cooler than room temperature: when the ampule was cooled the air "shrank" and drew in some water. There are other scenarios but all involve temperature changes.

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#15
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Re: Mystery Behind Glass Ampule

09/27/2017 3:44 PM

R&Ddoc did mention that they fill these vials with a volatile organic (monomer).

Normally they could be delivered under the minute pressure of the monomer vapor.

A failed vial, would evaporate slowly (or quickly at high altitude?) and thus when dipped into water, cool the head space and draw some in by pressure difference, and also partially due to capillary action (even on a so-called closed end tube).

Wet fingers during the vial dipping would not hurt the cooling process.

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#19
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Re: Mystery Behind Glass Ampule

09/27/2017 5:04 PM

The customer believes the ampoule was packed empty (he does not admit the possibility of micro cracks in the glass, nor evaporation of the content during transport).

Behavior of monomer is very similar to those of gasoline.

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#24
In reply to #19

Re: Mystery Behind Glass Ampule

09/28/2017 7:36 AM

Obviously your customer knows nothing about glass. You don't really have to educate your customer because there is likely no return on that investment. Just promise him that you will solve the problem.

A series of bubbles where two surfaces come together is all it takes. It takes a microscope to see that.

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#26
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Re: Mystery Behind Glass Ampule

09/28/2017 9:23 AM

The Chinese are just recently starting to get into the program of Quality Management. Chinese are considered second rate manufacturers to the world so this customer is over reacting in opposition to the reputation that his country has earned for themselves. A lot of Chinese companies are on par of where they need to be to be competitive. This Customer is trying to get something for nothing out of it by accusing the seller of cheating them, rather than just simply notifying the seller that one of the vials was defective can they send a replacement. Even the Japanese, who are far more strict in quality compliance than the US has defective products get through once in awhile. I'd say 1 defective out of 5000 is pretty good, considering they haven't had this problem come up before out of how many of this product overall that has been sold.

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#20
In reply to #14

Re: Mystery Behind Glass Ampule

09/27/2017 5:06 PM

I considered the temperature issue as well. WAter was at room temp during the test we made.

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#22
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Re: Mystery Behind Glass Ampule

09/27/2017 5:47 PM

If it was held in the hand, the ampule most likely was warmer than the water temperature.

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#23
In reply to #14

Re: Mystery Behind Glass Ampule

09/28/2017 12:20 AM

Ampule is relatively thin walled and the air in it could be expelled out by picking heat from finger tips. Once immersed, the glass gets cooled, so is the air in it. This could cause a partial vacuum.

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#16

Re: Mystery Behind Glass Ampule

09/27/2017 3:49 PM

Is the water at the same temperature as the ampule? Perhaps the cooling of the air inside the ampule pulled the water in when it was dunked in the water bath. Just a random thought.

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#17
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Re: Mystery Behind Glass Ampule

09/27/2017 4:08 PM

According to Randall, he claims first rights to this answer.

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#29
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Re: Mystery Behind Glass Ampule

09/28/2017 12:41 PM

You would be correct. I (perish the thought) only read his first line about capillary action and assumed the rest of the thoughts were on capillary action. (My bad)

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#21
In reply to #16

Re: Mystery Behind Glass Ampule

09/27/2017 5:07 PM

yes, same temp

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#27

Re: Mystery Behind Glass Ampule

09/28/2017 11:10 AM

There are probably three or four mechanisms that would get water into the ampule.

Capillary action is one.

Thermal expansion and contraction leading to the air volume inside shrinking.

Barometric pressure changes. The volume of air inside and the ampule acting like a standing column barometer

Dissolution of gas in the ampule into the liquid surface, sometimes referred to as headspace.

Any and all could lead to what you observe. Bottom line is that if the water gets in, then the seal leaked.

If you are looking for a quality test to eliminate seal leakage as a QA concern, you could either continuous or batch weigh the filled ampules, put them in a vacuum for a period of time and then reweigh to verify no weight loss due to seal leakage. A continuous process would cost for initial equipment, but could be run with little to no labor charge for the process. Your company will need to decide whether the cost of such a process countermeasure is justified in customer satisfaction or contract requirements.

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#30

Re: Mystery Behind Glass Ampule

09/28/2017 5:37 PM

May be an increase in atmospheric pressure ocurred !

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