RonPaul2012
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Density question.
I have an elementary question on density.
Suppose you have a solid compound and lets say that compounds density is 15g/cm3.
My question is how is that density quantified e.g what is the criterion for this measurement ?
Is it pressed until it can't be pressed anymore ?
When you synthesis a compound and then you put it in a graduated cylinder and get the density it's always going to be much less than the textbooks
said density.
I'm sure I could find the answer to my question in a textbook but
I really don't have time.
I'm not looking to be spoon fed , I'm just curious 
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Endimion17
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Solids can be compresed infinitely... forming black holes. 
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GreenD
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When you synthesis a compound and then you put it in a graduated cylinder and get the density it's always going to be much less than the textbooks
said density.
why is this?
ʃ Ψ*Ψ
Keepin' it real.
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RonPaul2012
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Quote: Originally posted by GreenD  | When you synthesis a compound and then you put it in a graduated cylinder and get the density it's always going to be much less than the textbooks
said density.
why is this? |
Air in between the granules and such.
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GreenD
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What granules lol?
Density usually refers to a liquid.
Solids that have a given density are measured by their mass divided by their volume. For solids like metal this is pretty easy - no air pockets.
Measure mass, measure volume.
For other compounds that form crystals (which don't really ever need a density measurement) you put them in a grad cylinder and measure the
displacement of a liquid. You can centrifuge to remove any gas in any pockets...
Check this link out for more info: http://notrickszone.com/wp-content/uploads/2011/10/spoon-fee...
[Edited on 8-3-2012 by GreenD]
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Keepin' it real.
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RonPaul2012
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| Quote: Originally posted by GreenD | What granules lol?
Density usually refers to a liquid.
Solids that have a given density are measured by their mass divided by their volume. For solids like metal this is pretty easy - no air pockets.
Measure mass, measure volume.
For other compounds that form crystals (which don't really ever need a density measurement) you put them in a grad cylinder and measure the
displacement of a liquid. You can centrifuge to remove any gas in any pockets...
Check this link out for more info: http://notrickszone.com/wp-content/uploads/2011/10/spoon-fee...
[Edited on 8-3-2012 by GreenD] |
This is this answer that I was looking for , could you go into a little more
detail , please
When I was talking about air pockets, I was reffering to what I think is called "apparent" or bulk" density.
I would really like to know how to measure crystalline density could you post a reliable how to ?
[Edited on 8-3-2012 by RonPaul2012]
[Edited on 8-3-2012 by RonPaul2012]
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RonPaul2012
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Here is a good link that I found http://lib.njutcm.edu.cn/yaodian/ep/EP5.0/02_methods_of_anal...
2.2.42. DENSITY OF SOLIDS
The density of solids corresponds to their average mass
per unit volume and typically is expressed in grams per cubic
centimetre (g/cm3) although the International Unit is the
kilogram per cubic meter (1 g/cm3 = 1000 kg/m3).
Unlike gases and liquids whose density depends only on
temperature and pressure, the density of a solid particle also
depends on its molecular assembly and therefore varies with
the crystal structure and degree of crystallinity.
When a solid particle is amorphous or partially amorphous,
its density may further depend upon the history of
preparation and treatment.
Therefore, unlike fluids, the densities of two chemically
equivalent solids may be different, and this difference
reflects a difference in solid-state structure. The density of
constituent particles is an important physical characteristic
of pharmaceutical powders.
The density of a solid particle can assume different values
depending on the method used to measure the volume of the
particle. It is useful to distinguish three levels of expression
of density:
— the crystal density which only includes the solid fraction
of the material ; the crystal density is also called true
density ;
— the particle density which also includes the volume due
to intraparticulate pores,
— the bulk density which further includes the
interparticulate void volume formed in the powder bed;
the bulk density is also called apparent density.
[Edited on 8-3-2012 by RonPaul2012]
[Edited on 8-3-2012 by RonPaul2012]
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