Unless someone has already worked it out (and therefore knows the volume of a "sodastream" cylinder) that could absorb a bit of brain power. My brain ain't up to it, but I had a look all the same. This probably contains the information needed:
http://www.linde-gas.pt/en/legacy/attac ... m:03-25938
Wish I hadn't dug it up, 'cos it says:
Yikes! It also repeats some of what I've been saying:It is highly inadvisable to transfer carbon dioxide from one cylinder to another.
To work out the answer to your question you need to know the volume of the cylinder and the weight of gaseous CO2 that will occupy that volume at about 57BAR and room temperature. And even that might not be enough as it will assume only gas transfers and I think some condensate will (must?) transfer even if the donor cylinder is upright? It also assumes room temperature, and the action of changing liquid CO2 to gas is going to drop the temperature well below that.The pressure in a CO2 cylinder depends solely on temperature. At 20°C, for example, it is 57 bar. Even an almost empty CO2 cylinder remains at 57 bar at 20°C, as long as it contains the liquid phase. This means that the contents of a CO2 cylinder cannot be determined by measuring its pressure, but only by weighing.
It's all getting too much for my simplistic understanding … is someone else going to come along and fill in the blanks?