I got 1 gallon of Muriatic Acid yesterday for about $6. Muriatic Acid is something like either 30% or 40% hydrochloric acid and I bought it just to play around with and what not (dissolving metal is always fun isnt it?

). Today my room mate was bitching at me about how the fumes are toxic and we're all gonna die blah blah. I compared it to Lime Away saying both were very strong acids, very poisonous and very corosive. He didn't believe me so I got the Lime Away out of the cupboard and looked at the label..... Lime Away is 46% hydrochloric acid!
Muriatic Acid is basically the same as Lime Away but it's a bit weaker. The major thing is that it costs WAY less. You'll never be able to find 1 gallon of Lime Away for $6 at a hardware store like you will with Muriatic Acid

I poured some of the acid on the concrete outside my building it started foaming and turning yellow and stinking immediately.... I don't think strength is a problem