04-25-04 20:56
No 503036
The fucking search engine has not been working and I can't find a reference to the density of pseudoephedrine on the web. Anybody have it?
(Chief Bee)
04-25-04 21:04
No 503037
The density of crystalline compounds is seldom determined, as it fluctuates with crystal size and recrystallization solvent.
The Hive - Clandestine Chemists Without Borders
(Wizard Master)
04-26-04 00:08
No 503068
The density of ephedrine is also affected by the hydration of the ephedrine molecule with 1/2 mole of water.
Unless ephedrine is anhydrous, (low boiling point azeoptropic distillation) you can not determine the density accurately?
(Hive Bee)
04-26-04 14:25
No 503188
I would think that freebase in the liquid state might have a consistent density however. possibly even as the solid. I think if it were purified/crystallised and melted in a small graduated cylinder so that it liquified and gave you a clear volume reading, then weigh the material, and you should get your density.
polar compounds such as alkaloid salts are useless with density determinations for the reasons that rhodium said (water of crystallisation, contaminants etc etc) and besides which, what are you going to use to measure the density with? Density is much easier to measure with liquids (like i said, in a small graduated cylinder), or with solids you can use liquid displacement to measure it's true volume. Don't bother trying to measure the density of the salt. I don't think that liquid displacement would be a sensible way to measure the freebase as it would partially ionise it or force you to use an alkaline solution which itself has already had it's density altered.
Also note that liquids and solids have density variations caused by temperature, so you must state the temperature in a proper accurate density measurement of a compound which is subject to thermal contraction and expansion due to temperature changes.
(Chief Bee)
04-26-04 16:48
No 503212
I would think that freebase in the liquid state might have a consistent density however
Correct, as long as the temperature is constant. Most liquids expands as they heat up and contracts as they cool down.
possibly even as the solid.
That is however incorrect. Solids occur in several different isomorphs, each with its own density, depending on how closely the molecules are packed. To cite an extreme example, diamond, graphite and fullerene C60 are all 100% carbon, but the density is 1.65, 2.20 and 3.51 g/cm3 respectively.
The Hive - Clandestine Chemists Without Borders
(Hive Bee)
04-26-04 19:04
No 503232
buckminsterfullerene, graphite and diamonds may be pure carbon compounds but especially in the case of the former, obviously it's going to have a different density being a hollow spherical geodesic dome thing.
solid or liquid freebase *would* be consistent at a given temperature because it is the same stuff, the intermolecular forces are the same with any given sample of the identical pure compound at different temperatures and pressures.
The real point though, is that this, as a method of identifying a material, or the purity of a material, is far inferior to chromatography and mp/bp determination (of which i would be inclined to say the former is the simplest and cheapest and most accurate, especially tlc).
(Stranger)
04-26-04 19:32
No 503240
a distant possibility would be to formulate a space-filling model of its atoms and find the volume per molecule. with that and the molecular weight, you'd have a maximum density (accurate only if the molecules were perfect rectangles) @ 0 K .. neglecting 'packing' considerations as influenced by shape and intermolecular forces. ..this amounts to the density of a single molecule.
it might be useful, though, by comparison to similarly calculated values which are also 'known' in macroscopic quantities.
(Stoni's sexual toy)
04-27-04 01:55
No 503287
The density for freebase will be something between 0.9 and 1.4 and the HCl will probably be between 1.5 and 1.8. That's crystal density both times.
But why is this relevant? Actually it doesn't matter since you cannot determine those densities easily and accurately in your basement anyway, and since most other compounds have densities in the same range.
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