Author Topic: density of solid bromine  (Read 2964 times)

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starlight

  • Guest
density of solid bromine
« on: October 26, 2004, 08:13:00 PM »
Someone mentioned an interesting situation a while back and I was wondering if anyone here knew the answer.

The issue was to do with the storage of liquid bromine.

The owner of the bromine wished to store it outside and below ground as it would remain undisturbed this way and additionally far away from human habitation.

She stated that the ambient temperature outside was likely to fall below negative 7.2C during the storage period. The bromine would therefore probably solidify if it were stored outside.

There was therefore a concern that the bottles may shatter if bromine expands as it freezes like water does (most things don't, but the following URL makes you think it might be possible:

http://groups.google.co.uk/groups?hl=en&lr=&selm=1994Aug10.173135.2685%40inet.d48.lilly.com

. Pretty anecdotal, but storage of bromine is not something that you can afford to mess up.

The data that can be found via google on the density of solid Bromine is pretty limited and only provides info for Bromine at 5 Kelvin and 123 Kelvin. Both these data points suggest that solid bromine is more dense at these temperatures than it is as a liquid. However, the density of solid bromine at -8 Centigrade may be lower than liquid bromine at -6C.

Does anyone here have any experience with frozen bromine or know the density of solid bromine at say -8C? Do you think bottles of bromine may break upon freezing (this is obviously a small scale environmental disaster).

Inside storage was deemed to be out of the question as this meant close to human habitation and even when locked away a fire can cause toxic clouds of bromine leading to injury or death for a fire crew that is not fore-warned.

Rhodium

  • Guest
Bromine bottles do not break when frozen
« Reply #1 on: October 26, 2004, 09:03:00 PM »
Does anyone here have any experience with frozen bromine or know the density of solid bromine at say -8C? Do you think bottles of bromine may break upon freezing

Bromine bottles do not break when frozen, and "bromine ice" sinks. The link you gave only said that bromine would melt under pressure, not that it expands when solidifying.


starlight

  • Guest
doesn't one follow from the other
« Reply #2 on: October 26, 2004, 09:44:00 PM »
Isn't the reason that a substance melts under pressure the same as the reason that something expands upon freezing?

These links (although pseudo scientific) suggest that this is the case:

http://www.pa.msu.edu/~sciencet/ask_st/112091.html


http://van.hep.uiuc.edu/van/qa/section/States_of_Matter_and_Energy/Properties_of_Water/889132841.htm



On a phase diagram for water, the melting curve or fusion curve of ice/water has a negative slope.

Isn't this due to the fact that when ice melts, the molar volume decreases? Does this not also mean that ice actually melts at lower temperature when the pressure is higher?

Sorry for not understanding, and thanks for the information that bromine sinks on freezing.

Rhodium

  • Guest
density of solid Bromine
« Reply #3 on: October 26, 2004, 10:57:00 PM »
The density of liquid Br2 at 293K is 3.119 g/cm3 and the density of solid Br2 at 123K is 4.05 g/cm3

Thus bromine contracts upon cooling:

http://www.newton.dep.anl.gov/askasci/chem03/chem03318.htm



293 K, 3.119


hypo

  • Guest
weird logic...
« Reply #4 on: October 26, 2004, 11:25:00 PM »
that's just two data points, it doesn't tell us anything about local density minima.

solid H2O at 123K probably has a density >1g/ml too and yet it expands on freezing...


Barium

  • Guest
Nope
« Reply #5 on: October 27, 2004, 12:33:00 AM »
Something which expands as it freezes can't have the same density frozen as in liquid form.
If one mole water occupies 18 ml when liquid and e.g. 20 ml when frozen it has the density 1 as liquid but 0.9 as frozen.



Edit:
Me and my fucking calculations. Note that the above was only an example (e.g.).


hypo

  • Guest
expansion on freezing
« Reply #6 on: October 27, 2004, 01:00:00 AM »
"expanding on freezing" only means that it expands when turning from
liquid to solid. after that the solid usually shrinks with further cooling.
but only to a small extent. (my assertion of ice at 123K having a density
>1 g/ml was wrong, i way overrated the effect)

and then there's the possibility of phase conversion which could lead to
a rather big density jump! so given two distant data points, i wouldn't bet
my balls on the course of the density curve.

that being said, i don't think bromine is one of those seldom compounds
that expand on freezing. the ones i know are water, silicon and antimony.


indole_amine

  • Guest
huh???? ;^)
« Reply #7 on: October 27, 2004, 01:10:00 AM »
Barium, you said: "one mole water occupies 18 ml when liquid and e.g. 20 ml when frozen it has the density 1 as liquid but 1.11 as frozen."

..So one mol water weighs 18 grams when liquid (18ml x 1g/ml) but 22.2g when frozen (20ml x 1.11g/ml)??

Durely not.

Water has its greatest density at 3.98°C BTW. So it contracts when cooling, but expands when cooled further to below this temp. Due to the fact that one mol of a certain substance can't simply change its weight without changing its identity  :) , it changes its volume (the crystal structure of H2O is very porous..) and expands further upon freezing, until it reaches a density of ~0.9g/cm3.



Oh, and Hypo: I know two other substances that expand on freezing: gallium and wismuth...



indole_amine

hypo

  • Guest
heh...
« Reply #8 on: October 27, 2004, 01:18:00 AM »
i'm sure barium was talking about inverse density a.k.a specific volume expressed in ml/g.  ;)


indole_amine

  • Guest
huh(2)
« Reply #9 on: October 27, 2004, 01:37:00 AM »
Bullshit. There isn't anything like "inverse density", and volume isn't weight-specific - it is defined solely as cm3 or ml, not per weight...

Weight(g) / Volume(cm3) =  Density(g/cm3)

Please don't expect me to give any reference for this..

(oh, and tantal is the only element that is resistant to pure bromine, AFAIK)

indole_amine

Captain_America

  • Guest
Additional info
« Reply #10 on: October 27, 2004, 01:40:00 AM »
Good work indole_amine.. I thought I'd contribute to your disscussion by pointing out that 1 kg bromine corresponds to a volume 0.0007076044624084775 cord foot (cd ft)...

Just wondering, is this thread going to end up being one of those all-time-lows?

indole_amine

  • Guest
additional addon ;^)
« Reply #11 on: October 27, 2004, 02:01:00 AM »
Platinum is the only one of the noble metals that doesn't react with bromine at all. Does anyone know the price for galvanic platinizing the inside of a metal box? For safe storage?  :)


indole_amine

MargaretThatcher

  • Guest
Density
« Reply #12 on: October 27, 2004, 02:31:00 AM »
density = mass / volume (not weight)

Units will be kg/m3  or multiples thereof.

The density of ice depends on its phase (there being 14 known), temperature and pressure.

I can't find a phase diagram for bromine and the yahoo groups post seems to have disappeared.


lugh

  • Guest
Expansion in the Liquid State
« Reply #13 on: October 27, 2004, 02:59:00 AM »
According to Thorpe's Dictionary of Applied Chemistry bromine has a coefficient of expansion of 0.0011 between 25 ° and 30 °  :)  It also states that bromine crystallizes in an orthorhombic system, and that as the temperature decreases, the color fades to a pale yellow at the temperature of liquid air, the reference given is Proc Roy Soc A 88 348, 313 (1913)  ;)  Little Giant lists aluminum as a suitable sealing material for wet bromine, much cheaper than platinum  ;D  If SWIL was going to do attempt such a thing, a glass bottle would be packed into an aluminum can in case some unlucky person start digging in the same place  8)


indole_amine

  • Guest
Al?
« Reply #14 on: October 27, 2004, 03:33:00 AM »
Aluminum not reacting with halogens? At least not with bromine? I wouldn't rely on that.. :)

I read once that tantal and platinum would be the only elements that don't react with pure bromine, and since it is one of the most corrosive elements (along with fluorine and chlorine) I doubt that aluminum would be useful for constructing protective vessels for bromine storage (even iodine reacts readily when heated slightly with Al AFAIK...)

Maybe "wet bromine" means the common 0.2 bromine/H2O solution known as "bromine water"?


indole_amine

Rhodium

  • Guest
Note that this deals with wet bromine only
« Reply #15 on: October 27, 2004, 03:40:00 AM »
Only wet bromine can be stored in aluminum vessels. This because the water hydrolyzes the aluminum bromide formed, making aluminum oxides and hydroxides.  These compounds coat the aluminum, protecting it from further attack.


hypo

  • Guest
specific volume
« Reply #16 on: October 27, 2004, 09:59:00 AM »
> There isn't anything like "inverse density", and volume isn't weight-specific

of course there is:

http://www.grc.nasa.gov/WWW/K-12/airplane/specvol.html



http://www.google.com/search?q=%22specific+volume%22


=> over 40000 hits


indole_amine

  • Guest
anyway
« Reply #17 on: October 27, 2004, 02:22:00 PM »
It is commonly used for gases only AFAIK.

And besides, barium didn't mention "specific" or "inverse", just "volume"´and "density" alone. If he meant inverse density or specific volume, he should've said so.

And besides, it's about if bromine contracts or expands upon freezing, not about wierd, uncommon specifications of density or volume.


indole_amine

hypo

  • Guest
i was only joking
« Reply #18 on: October 27, 2004, 04:13:00 PM »
pretty low specific volume today, hunh?

of course i was only joking about the fact that barium made the division the wrong
way around, a pretty common thinko (especially when you've fried your brain by
using too much lsd).


> Just wondering, is this thread going to end up being one of those all-time-lows?

oh, you _will_ wonder how deep we can go!  :P