Muriatic means a specific percentage formulation does it not? Like 18% or so.
There is no hard and fast specific percentage concentration for Muriatic acid. You may find it at 31.5% or you may find it at 20% or 14.5%. The stronger stuff is more often sold for industrial applications and the weaker stuff is sold for things like descaling and cleaning lime buildup in swimming pools, hot tubs, shower stalls, etc. Both Hydrochloric acid and Muriatic acid are HCl, but pure Hydrochloric acid will be clear and Muriatic will usually have a yellowish color due to impurities such as iron or traces of Sulphuric acid. So the term Muriatic acid isn't really an archaic term, but one that denotes a level of purity. Muriatic is generally cheaper because it is generally less concentrated and less pure, but it all depends upon where you buy it. I'm fortunate enough to live near a chemical supply company that will sell small quantities of higher concentration stuff for far less than the watered down versions you might buy at Lowe's or Home Depot.
Remember the rule for mixing acids and water when diluting. Always go in alphabetical order. A for Acid and W for Water. Pour the Acid slowly into the Water, because if you pour water into concentrated acid, it may sputter and splash back at you.
