does anybody know how a gas cylinder measuring 6" dia and 32" tall can
have 80 cu ft of gas? how is this figured?

"mawtg" wrote
does anybody know how a gas cylinder measuring 6" dia and 32" tall can
have 80 cu ft of gas? how is this figured?


Yes ... the gas volume (in your case 80 cubic feet) is when it is at
atmospheric pressure. By compressing the gas, you can make it fit into a
smaller volume, but the pressure goes up accordingly.

Take a look at this page (hint ... I did a google search using the search
term ' gas cylinder volume ' without the quotes):

http://www.engineeringtoolbox.com/co...me-22_843.html

Seems some old dead fellow (before he died) came up with Boyle's Law (betcha
his name was Boyle).

Simply put, if you squeeze 80 cubic feet of gas at atmospheric pressure into
a vessel with a volume of 40 cubic feet, the pressure in that vessel will be
twice atmospheric pressure.


Hope this helps, but I'm still trying to figure out what this has to do with
woodworking, other than it's a gas when it goes well!


Regards,


Rick

On Thu, 25 Aug 2005 02:01:13 GMT,
lid (mawtg) wrote:

does anybody know how a gas cylinder measuring 6" dia and 32" tall can
have 80 cu ft of gas? how is this figured?


it's compressed.

lid (mawtg) wrote:


does anybody know how a gas cylinder measuring 6" dia and 32" tall can
have 80 cu ft of gas? how is this figured?


You are referred to a high school chemistry text for a detailed
explanation of Boyle's Law.

The same text will also give you the density of the gas in question at
standard pressure and temperature specifications.

Next you weigh the cylinder to get a gross weight, then subtract the
cylinder weight to get net weight of the compressed gas.

After that, it is a basic math problem.

Lew

On Thu, 25 Aug 2005 02:17:20 GMT, "Rick M" wrote:



http://www.engineeringtoolbox.com/co...me-22_843.html

Seems some old dead fellow (before he died) came up with Boyle's Law (betcha
his name was Boyle).


The Engineering Gods will smite you for that one.

On Thu, 25 Aug 2005 02:17:20 GMT, "Rick M"
wrote:

"mawtg" wrote
does anybody know how a gas cylinder measuring 6" dia and 32" tall can
have 80 cu ft of gas? how is this figured?

Simply put, if you squeeze 80 cubic feet of gas at atmospheric pressure into
a vessel with a volume of 40 cubic feet, the pressure in that vessel will be
twice atmospheric pressure.

...it can also be liquified, depending upon the gas; e.g. propane. CO2
doesn't liquify under pressure, it becomes solid [dry ice.] Either
way a lot can be fit into a little space.

Guess who wrote:
On Thu, 25 Aug 2005 02:17:20 GMT, "Rick M"
wrote:

"mawtg" wrote
does anybody know how a gas cylinder measuring 6" dia and 32" tall can
have 80 cu ft of gas? how is this figured?

Simply put, if you squeeze 80 cubic feet of gas at atmospheric pressure into
a vessel with a volume of 40 cubic feet, the pressure in that vessel will be
twice atmospheric pressure.

..it can also be liquified, depending upon the gas; e.g. propane. CO2
doesn't liquify under pressure, it becomes solid [dry ice.] Either
way a lot can be fit into a little space.


ISTR that CO2 will liquify under pressure at room temperature.

It won't condense into liquid at atmospheric pressure though,
goes straight to solid.

Water does the same, gas to solid, solid to gas (sublimation)
with no liquid phase at very low presssure.

--

FF

mawtg wrote:
does anybody know how a gas cylinder measuring 6" dia and 32" tall can
have 80 cu ft of gas? how is this figured?

The answer is that it can't. It can only hold
about 1/2 cubic foot (if I did the math
correctly). Doesn't matter what the gas is,
doesn't matter what the pressure is, it is always
the same volume because gases expand to fill the
volume of the container. The question is
illogical probably based on a statement that was
incomplete, or part of which was ignored in
stating the question.

And by the way, any amount of gas in the cylinder
can have a volume of 80 cu ft if the pressure is
sufficiently lower that the gas in the cylinder.

If you want to measure the amount of gas, you have
to give a volume and a pressure, or something by
which the number of atoms/molecules of the gas can
be calculated.

It is unfortunate that school don't teach, or the
students don't learn, the states of matter and the
basic properties of those states. Seems to me
that would be more important that the colors of
the rainbow and a few other things kids are taught.

George E. Cawthon wrote:
mawtg wrote:
does anybody know how a gas cylinder measuring 6" dia and 32" tall can
have 80 cu ft of gas? how is this figured?

The answer is that it can't.
...
It is unfortunate that school don't teach, or the
students don't learn, the states of matter and the
basic properties of those states. Seems to me
that would be more important that the colors of
the rainbow and a few other things kids are taught.


A standard measure of gas is the _standard cubic foot_ which
is the amount of gas that will occupy a volume of one cubic
foot at standard temperature and pressure, usually abbreviated
SCF. You see it most often in reference to volumetric
flow as through a blower or a fan, SCF/minute or whatever.

The standard pressure is one atmosphere. Unfortunately the
standard temperature is either 0 degees C or 'room temperature'
(which I think is around 70 degrees F) depending on which
standard is used, though that makes only a small difference.

So when you buy gas by the cubic foot, you are buying by
the standard cubic foot, the seller usually omits the
word 'standard'.

--

FF

In article ,
"Rick M" wrote:

Yes ... the gas volume (in your case 80 cubic feet) is when it is at
atmospheric pressure. By compressing the gas, you can make it fit into a
smaller volume, but the pressure goes up accordingly.

as does the temperature

In article ,
"Rick M" wrote:

Seems some old dead fellow (before he died) came up with Boyle's Law (betcha
his name was Boyle).

....errrrmmm...is this why we 'boyle' water?

....could be where that word came from...

A faraday keeps the doctor away?

Back to sleep.

George E. Cawthon wrote:
mawtg wrote:
does anybody know how a gas cylinder measuring 6" dia and 32" tall can
have 80 cu ft of gas? how is this figured?

The answer is that it can't. It can only hold
about 1/2 cubic foot (if I did the math
correctly). Doesn't matter what the gas is,
doesn't matter what the pressure is, it is always
the same volume because gases expand to fill the
volume of the container. The question is
illogical probably based on a statement that was
incomplete, or part of which was ignored in
stating the question.


Not quite. Your statement is incomplete as well. That .5 cubic foot that you
suggest only holds true at atmospheric pressure. If you compress the gas
within, you can hold virtually any amount up to the bursting pressure of the
tank. On 80 cf scuba cylinders which are only a little bigger than his example,
you'd charge them to about 200 atmospheres (3000 psi) to get the 80 cubic feet
packed in there. It is understood that the 80 cf measurement is what the
cylinder holds under pressure, not empty.

AGA Divator used to make twin 40 cf systems that required them to be pumped up
to 4400 psi. Now that is one hell of a lot of pressure. They were little
things that fit closely to your back but they were ungodly expensive and most
dive shops couldn't fill them. But they packed the same 80cf as the larger
cylinders.


--
Mortimer Schnerd, RN

VE

In article , Guess who wrote:

...it can also be liquified, depending upon the gas; e.g. propane. CO2
doesn't liquify under pressure, it becomes solid [dry ice.]

Not correct. CO2 cannot be *solidified* under pressure unless the temperature
is below -57 degrees C.

The triple point of CO2 is -57 deg C and 5.1 atmospheres: it can exist as a
solid, liquid, or gas at that temperature and pressure. It cannot exist in the
solid phase above -57 degrees, nor in the liquid phase below that point,
regardless of pressure.


--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

Robatoy wrote:
In article ,
"Rick M" wrote:
=20
=20
Seems some old dead fellow (before he died) came up with Boyle's Law (b=
etcha
his name was Boyle).
=20
=20
...errrrmmm...is this why we 'boyle' water?
=20
...could be where that word came from...
=20
A faraday keeps the doctor away?
=20
Back to sleep.


A Faraday keeps the engineer away -- then we don't have to endure bad=20
puns you see.


--=20
Will R.
Jewel Boxes and Wood Art
http://woodwork.pmccl.com
The power of accurate observation is commonly called cynicism by those=20
who have not got it.=94 George Bernard Shaw

In article ,
WillR wrote:

A Faraday keeps the engineer away -- then we don't have to endure bad
puns you see.

THAT will never happen..*WEG*.. btw, I have been meaning to ask you..did
you make it to the Muskoka Wood show?

In article ,
mawtg wrote:
does anybody know how a gas cylinder measuring 6" dia and 32" tall can
have 80 cu ft of gas? how is this figured?


The volume of the cylinder is piR^2H, so (roughly) 3.14X3X3X32=904 cu
inches. Divide by 12X12X12=1728 to convert cu in to cu feet=.523, lets
say 1/2 a cubic foot for convenience and to allow for cyl wall
thickness, etc. If it's a common gas cylinder it will usually be
compresssed to about 2500psi, so if we let that 1/2 CF expand by
releasing it tio atmospheric pressure of roughly 15psi, it would take
up .5X2500/15=83 cu ft, which is about right.
--

Larry Wasserman Baltimore, Maryland

"mawtg" wrote in message
...
does anybody know how a gas cylinder measuring 6" dia and 32" tall can
have 80 cu ft of gas? how is this figured?


The gas compresses and will until it turns to a liquid.

In article ,
mawtg wrote:
does anybody know how a gas cylinder measuring 6" dia and 32" tall can
have 80 cu ft of gas? how is this figured?


measuered as 80 cu ft, at _one_atmosphere_. Compressed to *much* higher
levels, to fit in the limited space.

In article ,
Roy put an RP here wrote:
On Thu, 25 Aug 2005 02:17:20 GMT, "Rick M"
wrote:



http://www.engineeringtoolbox.com/co...me-22_843.html

Seems some old dead fellow (before he died) came up with Boyle's Law (betcha
his name was Boyle).


The Engineering Gods will smite you for that one.

Sir Arthur Conan Boyle concluded that such gas behavior was "elementary,
my dear Watson, elementary!" *groan*

In article ,
WillR wrote:
Robatoy wrote:
In article ,
"Rick M" wrote:


Seems some old dead fellow (before he died) came up with Boyle's Law (betcha
his name was Boyle).


...errrrmmm...is this why we 'boyle' water?

...could be where that word came from...

A faraday keeps the doctor away?

Back to sleep.


A Faraday keeps the engineer away -- then we don't have to endure bad
puns you see.


Beware, the EE types have some that are real joules! Which they tell without
reluctance. Until people cry "no mho!"


However, an engineer did *not* commit the following atrocity --
An inmate of the insane asyslum, escaped, raping the window-cleaing lady
on the way; wherepon the local scandal-sheet rag ran a headling about it:
"Nut Screws Washer And Bolts"

On 24 Aug 2005 23:11:13 -0700, wrote:

ISTR that CO2 will liquify under pressure at room temperature.

It won't condense into liquid at atmospheric pressure though,
goes straight to solid.

When you're right, you're right. Trying to make the point, I said
something dumb. It happens.

Robert Bonomi wrote:
In article ,
Roy put an RP here wrote:

On Thu, 25 Aug 2005 02:17:20 GMT, "Rick M"
wrote:



http://www.engineeringtoolbox.com/co...me-22_843.html

Seems some old dead fellow (before he died) came up with Boyle's Law (betcha
his name was Boyle).


The Engineering Gods will smite you for that one.


Sir Arthur Conan Boyle concluded that such gas behavior was "elementary,
my dear Watson, elementary!" *groan*
A watched Boyle never goes to pot. [old Swedish saying]
j4

There is a phase diagram of CO2 at
http://www.science.uwaterloo.ca/~cch...phasesdgm.html, with
explanation.

Steve

"Guess who" wrote in message
...
On 24 Aug 2005 23:11:13 -0700, wrote:

ISTR that CO2 will liquify under pressure at room temperature.

It won't condense into liquid at atmospheric pressure though,
goes straight to solid.

When you're right, you're right. Trying to make the point, I said
something dumb. It happens.

Robatoy wrote:
In article ,
WillR wrote:
=20
=20
A Faraday keeps the engineer away -- then we don't have to endure bad=20
puns you see.
=20
=20
THAT will never happen..*WEG*.. btw, I have been meaning to ask you..di=
d=20
you make it to the Muskoka Wood show?


Yep -- got a few things -- it was small as usual, but I arranged for=20
some purchases for the next few months so...


--=20
Will R.
Jewel Boxes and Wood Art
http://woodwork.pmccl.com
The power of accurate observation is commonly called cynicism by those=20
who have not got it.=94 George Bernard Shaw

In article , jo4hn
wrote:

Robert Bonomi wrote:
In article ,
Roy put an RP here wrote:

On Thu, 25 Aug 2005 02:17:20 GMT, "Rick M"
wrote:



http://www.engineeringtoolbox.com/co...me-22_843.html

Seems some old dead fellow (before he died) came up with Boyle's Law
(betcha
his name was Boyle).


The Engineering Gods will smite you for that one.


Sir Arthur Conan Boyle concluded that such gas behavior was "elementary,
my dear Watson, elementary!" *groan*
A watched Boyle never goes to pot. [old Swedish saying]
j4

PUN FIGHT!!! (Starts off with a martial arts move from India, aka the
Punjab...)

wrote:
Guess who wrote:

On Thu, 25 Aug 2005 02:17:20 GMT, "Rick M"
wrote:


"mawtg" wrote

does anybody know how a gas cylinder measuring 6" dia and 32" tall can
have 80 cu ft of gas? how is this figured?

Simply put, if you squeeze 80 cubic feet of gas at atmospheric pressure into
a vessel with a volume of 40 cubic feet, the pressure in that vessel will be
twice atmospheric pressure.

..it can also be liquified, depending upon the gas; e.g. propane. CO2
doesn't liquify under pressure, it becomes solid [dry ice.] Either
way a lot can be fit into a little space.



ISTR that CO2 will liquify under pressure at room temperature.

It won't condense into liquid at atmospheric pressure though,
goes straight to solid.

Water does the same, gas to solid, solid to gas (sublimation)
with no liquid phase at very low presssure.


Actually that isn't true. The properties of water
are quite different from those of carbon dioxide.
Sublimation of water also occurs at normal
atmospheric pressures.

wrote:
George E. Cawthon wrote:

mawtg wrote:

does anybody know how a gas cylinder measuring 6" dia and 32" tall can
have 80 cu ft of gas? how is this figured?


The answer is that it can't.
...
It is unfortunate that school don't teach, or the
students don't learn, the states of matter and the
basic properties of those states. Seems to me
that would be more important that the colors of
the rainbow and a few other things kids are taught.



A standard measure of gas is the _standard cubic foot_ which
is the amount of gas that will occupy a volume of one cubic
foot at standard temperature and pressure, usually abbreviated
SCF. You see it most often in reference to volumetric
flow as through a blower or a fan, SCF/minute or whatever.

The standard pressure is one atmosphere. Unfortunately the
standard temperature is either 0 degees C or 'room temperature'
(which I think is around 70 degrees F) depending on which
standard is used, though that makes only a small difference.

So when you buy gas by the cubic foot, you are buying by
the standard cubic foot, the seller usually omits the
word 'standard'.


All true. But none of that changes the fact that
the question is erroneous.

Mortimer Schnerd, RN wrote:
George E. Cawthon wrote:

mawtg wrote:

does anybody know how a gas cylinder measuring 6" dia and 32" tall can
have 80 cu ft of gas? how is this figured?


The answer is that it can't. It can only hold
about 1/2 cubic foot (if I did the math
correctly). Doesn't matter what the gas is,
doesn't matter what the pressure is, it is always
the same volume because gases expand to fill the
volume of the container. The question is
illogical probably based on a statement that was
incomplete, or part of which was ignored in
stating the question.



Not quite. Your statement is incomplete as well. That .5 cubic foot that you
suggest only holds true at atmospheric pressure. If you compress the gas
within, you can hold virtually any amount up to the bursting pressure of the
tank. On 80 cf scuba cylinders which are only a little bigger than his example,
you'd charge them to about 200 atmospheres (3000 psi) to get the 80 cubic feet
packed in there. It is understood that the 80 cf measurement is what the
cylinder holds under pressure, not empty.

No it isn't. The volume of the cylinder is about
0.5 cubic foot, so the amount of gas that it
contains is ALWAYS 0.5 cubic foot; it doesn't make
any difference what the pressure is. Your 4th
sentence is also incorrect. At some pressure and
temperature you get liquid air which fills the
cylinder and at that point you can't put any more
air into cylinder since a liquid is only slightly
compressible. Your last point is also incorrect;
there was is no assumption about the pressure, and
it still matters not a whit since the cylinder
volume is 0.5 cubic feet so that is all the air it
can hold no matter what the pressure is as long as
it is gas.


AGA Divator used to make twin 40 cf systems that required them to be pumped up
to 4400 psi. Now that is one hell of a lot of pressure. They were little
things that fit closely to your back but they were ungodly expensive and most
dive shops couldn't fill them. But they packed the same 80cf as the larger
cylinders.



Your assumption is that we are talking about
cylinders of air for scuba diving at specific
pressure. The OP did not say anything that would
indicate that. He did provide enough information
that you could figure out the pressure needed in
the cylinder to have 80 cf of gas at one
atmosphere. Since it is 80 cf and cylinder is 0.5
cf it needs to be compressed about 160 times. One
atmosphere is about 15 psi, so the psi needed is
15 x 160 about 2700 psi. All of which has nothing
to do with what I said and the general lack of
understanding of states of matter.

George E. Cawthon wrote:

ISTR that CO2 will liquify under pressure at room temperature.

It won't condense into liquid at atmospheric pressure though,
goes straight to solid.

Water does the same, gas to solid, solid to gas (sublimation)
with no liquid phase at very low presssure.


Actually that isn't true.

Sure it is. Water does just that.

The properties of water
are quite different from those of carbon dioxide.
Sublimation of water also occurs at normal
atmospheric pressures.

I didn't say that water could did sublimate at normal atmospheric
pressure. The vapor pressure of water over ice is non zero, same
as for a lot stuff.

I said water goes gas to solid and solid to gas (sublimation)
with no liquid phase at very low presssure, which is true.
Carbon dioxide does the same, at atmospheric pressure, gas to
solid, solid to gas, with no liquid phase.

--

FF

George E. Cawthon wrote:
No it isn't. The volume of the cylinder is about
0.5 cubic foot, so the amount of gas that it
contains is ALWAYS 0.5 cubic foot; it doesn't make
any difference what the pressure is.

Within the cylinder, yes. But cylinders aren't sold according to their empty
volume; they're sold and rated according to the volume of gas they can hold at
their rated pressure.



Your 4th
sentence is also incorrect. At some pressure and
temperature you get liquid air which fills the
cylinder and at that point you can't put any more
air into cylinder since a liquid is only slightly
compressible.


OK, I'll give you that point. My bad. But I'll bet the tank will blow long
before the air liquifies. 3000 psi scuba cylinders will blow the safety disk at
around 4000 psi; get hydrotested at 5000 psi, and will catastrophically fail at
around 7500 psi. Will air liquify at 500 ATM? What gases would? I pulled out
my trusty old CRC Handbook of Chemistry and Physics but couldn't find the
information.


Your last point is also incorrect;
there was is no assumption about the pressure, and
it still matters not a whit since the cylinder
volume is 0.5 cubic feet so that is all the air it
can hold no matter what the pressure is as long as
it is gas.


But it can certainly be pressurized to hold much more gas than .5 cubic feet.
Otherwise there's no way in hell it can hold more than it holds at one
atmosphere.



--
Mortimer Schnerd, RN

VE

Mortimer Schnerd, RN wrote:
George E. Cawthon wrote:

No it isn't. The volume of the cylinder is about
0.5 cubic foot, so the amount of gas that it
contains is ALWAYS 0.5 cubic foot; it doesn't make
any difference what the pressure is.


Within the cylinder, yes. But cylinders aren't sold according to their empty
volume; they're sold and rated according to the volume of gas they can hold at
their rated pressure.




Your 4th
sentence is also incorrect. At some pressure and
temperature you get liquid air which fills the
cylinder and at that point you can't put any more
air into cylinder since a liquid is only slightly
compressible.



OK, I'll give you that point. My bad. But I'll bet the tank will blow long
before the air liquifies. 3000 psi scuba cylinders will blow the safety disk at
around 4000 psi; get hydrotested at 5000 psi, and will catastrophically fail at
around 7500 psi. Will air liquify at 500 ATM? What gases would? I pulled out
my trusty old CRC Handbook of Chemistry and Physics but couldn't find the
information.



Your last point is also incorrect;
there was is no assumption about the pressure, and
it still matters not a whit since the cylinder
volume is 0.5 cubic feet so that is all the air it
can hold no matter what the pressure is as long as
it is gas.



But it can certainly be pressurized to hold much more gas than .5 cubic feet.
Otherwise there's no way in hell it can hold more than it holds at one
atmosphere.




No it can't. How can you get more than .5 cubic
feet of air inside a cylinder that only has .5
cubic feet of volume? Please explain how you can
get more volume inside a cylinder than the volume
of the cylinder. Inquiring minds want to know?

And why are you fixated on assumptions about the
cylinder? It is just a cylinder. You don't know
the purpose or anything else about the cylinder.

wrote:
George E. Cawthon wrote:

ISTR that CO2 will liquify under pressure at room temperature.

It won't condense into liquid at atmospheric pressure though,
goes straight to solid.

Water does the same, gas to solid, solid to gas (sublimation)
with no liquid phase at very low presssure.


Actually that isn't true.


Sure it is. Water does just that.


The properties of water
are quite different from those of carbon dioxide.
Sublimation of water also occurs at normal
atmospheric pressures.


I didn't say that water could did sublimate at normal atmospheric
pressure. The vapor pressure of water over ice is non zero, same
as for a lot stuff.

I know you didn't. You should have.

I said water goes gas to solid and solid to gas (sublimation)
with no liquid phase at very low presssure, which is true.

Not true, doesn't have to be very low pressure.
It happens all the time at atmospheric pressure.

Carbon dioxide does the same, at atmospheric pressure, gas to
solid, solid to gas, with no liquid phase.

In article , "George E. Cawthon" wrote:
wrote:

I said water goes gas to solid and solid to gas (sublimation)
with no liquid phase at very low presssure, which is true.

Not true, doesn't have to be very low pressure.

Certainly it *is* true. Or do you claim that water does *not* pass directly
between the solid and gaseous phases at very low pressures?

He stated that this occurs at very low pressures. That is true.

He did *not* state that it does *not* occur at normal pressures. You seem to
be under the impression that he did.

It happens all the time at atmospheric pressure.

Yes, thank you, we know that already. Who claimed that it didn't?

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

In article , "George E. Cawthon" wrote:

No it can't. How can you get more than .5 cubic
feet of air inside a cylinder that only has .5
cubic feet of volume? Please explain how you can
get more volume inside a cylinder than the volume
of the cylinder. Inquiring minds want to know?

By compressing it, of course, so that the same *mass* of air that occupies 80
cu ft at standard pressure now occupies only 0.5 cu ft and easily fits inside
the cylinder.

Do you really have a hard time understanding this concept? Or are you just
being pedantic? Inquiring minds want to know....

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

"George E. Cawthon" wrote in message
...
Mortimer Schnerd, RN wrote:

But it can certainly be pressurized to hold much more gas than .5 cubic
feet.
Otherwise there's no way in hell it can hold more than it holds at one
atmosphere.


No it can't. How can you get more than .5 cubic
feet of air inside a cylinder that only has .5
cubic feet of volume? Please explain how you can
get more volume inside a cylinder than the volume
of the cylinder. Inquiring minds want to know?

And why are you fixated on assumptions about the
cylinder? It is just a cylinder. You don't know
the purpose or anything else about the cylinder.

There's no need to be intentionally obtuse just to try to prove a point.
The subject contains the phrase "gas cylinder". Now, maybe in your world,
that's any old cylindrical object that contains matter in a gaseous form,
but most humans interpret that to mean a (mostly) cylindrical object
designed to contain a gas at pressure. It's obvious from the freakin'
question that the gas is pressurized...otherwise the question would have
never come up.

todd

"Doug Miller" wrote in message
t...
Do you really have a hard time understanding this concept? Or are you just
being pedantic? Inquiring minds want to know....

The phrase I used was "intentionally obtuse", but "pedantic" fits even
better.

todd

George E. Cawthon wrote:
wrote:
...

So when you buy gas by the cubic foot, you are buying by
the standard cubic foot, the seller usually omits the
word 'standard'.


All true. But none of that changes the fact that
the question is erroneous.

Did you ever see this show called Dr Who?

A gas cylinder is constructed like a tardis you see so that

George E. Cawthon wrote:
Mortimer Schnerd, RN wrote:
George E. Cawthon wrote:

No it isn't. The volume of the cylinder is about
0.5 cubic foot, so the amount of gas that it
contains is ALWAYS 0.5 cubic foot; it doesn't make
any difference what the pressure is.


Within the cylinder, yes. But cylinders aren't sold according to their empty
volume; they're sold and rated according to the volume of gas they can hold at
their rated pressure.




Your 4th
sentence is also incorrect. At some pressure and
temperature you get liquid air which fills the
cylinder and at that point you can't put any more
air into cylinder since a liquid is only slightly
compressible.



OK, I'll give you that point. My bad. But I'll bet the tank will blow long
before the air liquifies. 3000 psi scuba cylinders will blow the safety disk at
around 4000 psi; get hydrotested at 5000 psi, and will catastrophically fail at
around 7500 psi. Will air liquify at 500 ATM? What gases would? I pulled out
my trusty old CRC Handbook of Chemistry and Physics but couldn't find the
information.



Your last point is also incorrect;
there was is no assumption about the pressure, and
it still matters not a whit since the cylinder
volume is 0.5 cubic feet so that is all the air it
can hold no matter what the pressure is as long as
it is gas.



But it can certainly be pressurized to hold much more gas than .5 cubic feet.
Otherwise there's no way in hell it can hold more than it holds at one
atmosphere.




No it can't. How can you get more than .5 cubic
feet of air inside a cylinder that only has .5
cubic feet of volume?

You can if the cubic feet are _standard cubic feet_ because
a standard cubic foot of gas is independent of the actual
volume of the gas.

....

And why are you fixated on assumptions about the
cylinder? It is just a cylinder. You don't know
the purpose or anything else about the cylinder.

'tis reasonble assumption, given the question.

--

FF

Doug Miller wrote:
In article , "George E. Cawthon" wrote:

wrote:


I said water goes gas to solid and solid to gas (sublimation)
with no liquid phase at very low presssure, which is true.

Not true, doesn't have to be very low pressure.


Certainly it *is* true. Or do you claim that water does *not* pass directly
between the solid and gaseous phases at very low pressures?

He stated that this occurs at very low pressures. That is true.

He did *not* state that it does *not* occur at normal pressures. You seem to
be under the impression that he did.


It happens all the time at atmospheric pressure.


Yes, thank you, we know that already. Who claimed that it didn't?


Like to argue for the sake of it, Doug?

Inclusion of the stipulation of "very low
pressure" in his statement implies that very low
pressures are needed. Otherwise why throw it in?

Doug Miller wrote:
In article , "George E. Cawthon" wrote:


No it can't. How can you get more than .5 cubic
feet of air inside a cylinder that only has .5
cubic feet of volume? Please explain how you can
get more volume inside a cylinder than the volume
of the cylinder. Inquiring minds want to know?


By compressing it, of course, so that the same *mass* of air that occupies 80
cu ft at standard pressure now occupies only 0.5 cu ft and easily fits inside
the cylinder.

Do you really have a hard time understanding this concept? Or are you just
being pedantic? Inquiring minds want to know....


Possibly being pedantic, but more like trying to
indicate that sloppiness in writing results from
faulty thought processes or lack of information.
The point I was trying to make was a basic
understanding of states of matter would negate
that kind of question. The point was, and is,
that a gas occupies whatever space it is allowed
to occupy. And the volume it occupies, of itself,
tells nothing about the mass.