Some liquids are sold by volume ( like lubricants-sold in litres), where as some liquid chemicals etc… are sold by weight ( in Kgs) ??
what is the deciding factor ?
Also why is Liquified petroleum gas sold by weight ??
Gases that are sold in pressurised containers have to be sold by weight because the container (essentially a fixed volume) is always full, in terms of volume.
With some other things, it’s just a matter of tradition. If you buy bean seeds from a seed merchant that sells them from the sack, they’re measured in pints - presumably because scooping them out with a jug, levelling off then tipping into a bag was just a simpler thing to do than weighing them.
Also, with some products, like ice cream, I assume the reason they’re sold by volume rather than weight is because they contain variable amounts of air, so two “full” containers of the same size could contain rather different weights.
Seems to me that this is an argument for selling by weight - otherwise, you’re paying for that variable amount of air.
Not from the manufacturers’ point of view, it isn’t! Likewise, I doubt we’ll see cinema popcorn being sold by weight any time soon…
In the case of gases that liquefy at high pressure (e.g. propane) weight is a lot easier to measure directly than volume of liquid.
And pressurized gases that don’t liquefy (e.g. oxygen, nitrogen) are effectively sold by volume: the charge is often based on the size of the bottle and the pressure difference between empty and full. (To be sure, in many cases it’s simply a flat charge for a fill.)
Thanx for all replies…
But some industrial cleaning chemicals like Tri chloro ethylene ( banned in U.S , PROBABLY)were sold by weight .
I always wondered why ??