what is this huge urn used for?

the other day, while we were exploring the chinatown area in singapore, one of my fellow explorers excited called out to me: "come here and see this! do you know what this huge urn is used for?"

the gigantic urn was raised and resting on four pieces of bricks. it had a cover which could be slid open.

i do not if the chinese characters on the side of the urn will give the answer away.

answer to the quiz:

as victor has correctly guessed the answer, i have posted a picture of the inside of the urn. it was used by the restaurant for preparing soup in the small pots. the shop where we came across this urn or jar is called the old shanghai.