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Topic: volume by displacement  (Read 5286 times)

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Offline mallard

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volume by displacement
« on: April 24, 2012, 01:31:06 AM »
im looking for an accurate way to measure the displacement of water. I dont want to use a graduated cylinder, i want something more precise. Is there a machine or something with an electronic numerical output that i could use ? something very precise ? where can i buy one?
thanks for your time

Offline Arkcon

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Re: volume by displacement
« Reply #1 on: April 24, 2012, 08:00:49 AM »
That's a tall order, as you've stated it.  A graduated cylinder is very precise, when read properly by a trained (that is, taught the rule once or twice) operator.  Graduated pipettes are more precise, but you won't fit much of anything inside.  The greatest precision loss would be hidden air bubbles clinging to the object.  Those can be hard to dislodge reliably, depending on the shape of the object.  Unless you don't actually mean to use the term precision, and mean instead accuracy, or some type of term for "ease of use" or "need for automation with data recording" or something like that.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline mallard

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Re: volume by displacement
« Reply #2 on: April 24, 2012, 11:14:52 AM »
thank you for your reply

a glass pipet , i didnt think of that but that is not accurate enough for what im looking for.

no i do not mean ease of use. I want a truly precise machine. I dont believe looking at a minicus on a graduated cylinder is the most accurate way to measure something, trained or not, i put little faith in human eyes, at least for the tolerances im looking to determine. If i used a graduated cylinder everything im measuring would appear identical because im looking for very tiny inconsistencies ( almost like trying to remove the 1% contaiminates in a 99 % solution , very tough i know but its what i want).

I want something that measures volume that has the equivalant precesion of a lab scale.

i asked my chemistry teacher if such equipment exists , she said yes for commerical labs. This is the type of machine i am looking to buy. Im really just looking for someone to give me a company name where i can stat digging. I checked out Ohaus and Denver instruments , they do not sell the type of device im looking for.

i apperciate any input ,thanks

Offline Borek

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Re: volume by displacement
« Reply #3 on: April 24, 2012, 11:30:52 AM »
Why displacement of water? Are you interested in the volume of gas evolved?
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Offline fledarmus

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Re: volume by displacement
« Reply #4 on: April 24, 2012, 01:47:58 PM »

Offline Arkcon

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Re: volume by displacement
« Reply #5 on: April 24, 2012, 03:05:25 PM »
no i do not mean ease of use. I want a truly precise machine. I dont believe looking at a minicus on a graduated cylinder is the most accurate way to measure something, trained or not, i put little faith in human eyes, at least for the tolerances im looking to determine.

Talk to some more teachers, about some more definitions.   Accuracy is a measure of correct values.  Manual procedures are very accurate, our eyes and brains are very good at compensating for reading errors.  Manual procedures have somewhat less precision than instrumental procedures, because instruments are less prone to tiring out, but they are not more accurate than manual procedures, often less accurate.  Instruments also have automation capabilities, and better record keeping capabilities and more immune to bias, but none of those concepts are part of the scientific definitions of accuracy and precision.  I suspected you didn't know which one you meant, when I worded my first answer, and you shouldn't mix them up in the same paragraph like you did where I quoted above.

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If i used a graduated cylinder everything im measuring would appear identical because im looking for very tiny inconsistencies ( almost like trying to remove the 1% contaiminates in a 99 % solution , very tough i know but its what i want).

You can do that, but you may not get the accuracy you want, with the methods you describe, because ...

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I want something that measures volume that has the equivalant precesion of a lab scale.

So this 1% value needs to be determined as 0.9998% or 1.010 %, if I understand you?  But by volume displacement?  No, see if I wanted to do that, I'd use the mass, on a laboratory scale, and calculate volume using the density.

*[EDIT]*
Or I'd use a device like fledarmus: linked to, and a laboratory balance, to get density and mass, to calculate volume.

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i asked my chemistry teacher if such equipment exists , she said yes for commerical labs. This is the type of machine i am looking to buy. Im really just looking for someone to give me a company name where i can stat digging. I checked out Ohaus and Denver instruments , they do not sell the type of device im looking for.

And she said this device's name is ... ?  Because I'd like to see how it works.  I've used a variety of glassware, from volumetric flasks, to graduated cylinders, to pipettes both manual and electronic, to 2 or 3 decimal places with good accuracy (compared to a NIST standard) and reasonable precision (adequate to work to the 6 sigma standard.)  So yeah, manual is a possibility still in this world.

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i apperciate any input ,thanks

Remember that you wrote that once you've re-read my responses.

Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline mallard

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Re: volume by displacement
« Reply #6 on: April 24, 2012, 04:17:57 PM »
Densimeter , i think thats what im looking for. Thank you for that

Im not interested in knowing the actual volume or density of the metals im working with. Just how much water each individual piece will displace for comparison purposes. I have sorted them by length and weight , but the metal has odd angles, and so i feel there is something to be gained by measuring the displacement of water.

Or I'd use a device like fledarmus: linked to, and a laboratory balance, to get density and mass, to calculate volume.

can you tell me more about that ? i tried using google and nothing came up. Im not sure its what im looking for but i'd like to learn more.

i am sorry i have confused the two terms.

thank you for your time

My teacher does not know the name of the device she was referring to. That would be nice.


Offline Arkcon

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Re: volume by displacement
« Reply #7 on: April 26, 2012, 09:36:57 PM »
Are you aware of the relationship between density, mass and volume?  If you know the density, because the metal is all the same, you can calculate the relationship.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

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