Today at school I learned about butter.
We dissolved butter in ether and water. The fat and other fat-soluble components (like Vitamin A) dissolve in the ether, and the milk solids and salt and other stuff stay in the water. Then we separated it by draining out the water, and then evaporated off the ether. This left us with a lovely dish of fat.
About 84% of butter is fat!!!
The internet tells me about 1-2% of salted butter is salt.
No wonder it tastes good.