Antiseptic<<..I know they were filled to capacity,but the actual volume..<<NO PRESURE>>..of the containers was inadequate to hold the rated weight.>>..[presure]..more presure in..means more'weight'

<<I presume it has something to do with the temperature and hence density of the gas at the time of dispensing.>>..ok thats close but the fact is its all about presure..[low presure..[less volume]weight

see that presure you get from a tank..[the tank gets it from a tanker[but the tanker leaves the depo with full presure,..but it gradually gets less..[because it pasivly fills,ONLY by the presure left in the tank!

when the tanker only refills the tank to a low presure..[the tank itself can only refill your tank TO THAT PRESURE''..'EACH TANK HOLDS LESS as the presure falls...lol

<<the density of the gas will be significntly reduced.>>egsactly,the gas ISNT pumped in[unlike fiat currency]..its all passive presure, less presure means you get less gas..[WE ARE BEING RIPPED OFF constantly,because every refill gives less presure thus less gas...lol,..yet with more cash pumped into the ecopnomy it buys less..lol

<<I guess that weights and measures have never received a complaint, or they've put it in the too-hard basket.>>no they know..[but they also know we dont know...lol

just like we dont know about the fed being for private proffit,..so many known unknowns ..lol

gotta love the system that exploits us unknowingly

those who get the gas #[or the cash, at max presure,get full value]..at the max prenium time may get a full tank

[but how to know the tank presure?[or how to audit the fed,..thats too difficult]

we are the cash cow...just work and pay in fiat printed at whim

dont worry about inflation
just be happy there is 'gas' to inflate...lol

rehctub: "It is called 'convenience' and it is evrywhere we look today."

Maybe rehctub, but I don't find it much more convenient. I expect it is real convenient for the service station as they don't have to make staff available to fill the container, but not for me.

You could solve the problem in one swoop by putting the same connector the cars use on the gas bottle. Anti's point about partial fills is fixed, your problem with 1/2 filled bottles is fixed, the LPG bowser is metered and policed by weights and measures, the staff problem is fixed and my problem with price is fixed. But I expect if you did that, someone would then say it is unsafe because checks on the condition of the bottle aren't enforced. Mind you, no one checks the condition of the bottles in the cars.

You may be right there is some price to pay for convenience. If so it is a dammed high price - $26 to put $9 of product into a bottle. If it does really cost that amount to put LPG into a bottle we need a new system. Personally, I think the total lack of competition SWAPnGO has at the moment is the real problem.

oug, it's "liquid" petroleum gas. It's sold as the liquid, not as the gas, so the pressure of the evaporated gas is not the crtical factor determining the mass: it's the temperature of the liquid which affects the density.

The pressure of the gas phase will certainly be affected by the temperature in a relationship described by Boyle's Law, (PV=nRT) as will be the amount of gas evaporated, but as long as there is liquid present, it is likely to be a much greater contributor to total mass.

To use actual numbers:
LPG has a density of around 550kg/cu.m in its liquid phase and only around 1.7kg/cu.m in its gas phase.

That means a 9kg bottle must have a volume of about 9/0.55 litres or a bit over 16 litres. Even if there is only 1 litre of liquid and the rest gas, the liquid weighs 0.55kg and the gas only 25g. When the bottle is full, the gas phase mass is practically negligible.

This system was supposedly introduced for safety reasons.
With the proliferation of casual, young, unskilled and poorly paid service station workers there were increasing numbers of accidents in the old manual filling system which was quite dangerous. There were also issues around people filling unsafe and corroded tanks.

While I agree the current system seems to be a swindle I cant really think of any alternative. Can anyone else?

Did any of you complain to the place of purchase or filling company?
What did they say?

*Today I went to the local service station to swap my 9Kg BBQ gas bottle*

Ah that was on a Sunday. So for the bloke who works there to
turn up and stand around picking his nose, he'd be on double time
at least. Then workers comp added to that. Then payroll tax added
to that. Then holiday pay added to that. Then holiday leave loading
added to that. Then superannuation added to that. Then long service
leave added to that. Then his entitlements in case he needs to
be fired, as the business is losing money, so you the consumer
should wear that as well.

So how much profit was left?

Yabby: "So how much profit was left?"

A fair bit I'd say. His contribution was to take my cash and hand me a key. It was all over in 30 seconds.