The larger the canister, the higher the ratio of gas to container weight. The canister on the pic should be around 15kg of gas. Based on other similar canisters, the canister should weigh around 40kg when full. That makes the weight ratio about 3:5.

But for smaller canisters, for example this 1.5kg canister, the weight ratio drops to about 3:7.

You should still be able to easily tell the difference between empty and full, I was just interested in the gas to container weight ratios

It definitely liquefies under pressures needed to fill these cylinders. I don't have a regulator here, but exit pressures are around 900psi unregulated.

I was using it straight from the bottle unregulated to flush a bunch of iron sediment out of a 300' long loop of 1-1/2 and 2" hot water lines after I rehabbed and put back into service a 70 year old hot water storage tank. The tank had a bunch of tubercule buildup and ended up in the return line, killing pressure.

Incidentally during this visit I fried a 6,000 dollar variable frequency drive for the air handler when I got a slug of water to shoot out of the cut open plumbing about 10' across a room and hose down the unprotected VFD.

Whoops.