Where can I find these I need 10

Alchemist shops mostly, but you can very rarely find random fire atronchs running around and you can get fire salts from them.

Alchemists are your best bet.
Normally theyll only have one or two, so your best bet is to travel around a bit.

Buy them at alchemist shops or find them in dungeons.

Fire atronachs leave them when they die. Check alchemists shops.

ok thanks guys!

Fire Atronachs are sometimes found in Conjurer dungeons. They're the daedra I've encountered the most so far. Actually the *only* daedra I've seen, except for summoned Frost Atronachs...