31.45% muriatic acid

[gobot]

Will a muriatic acid with 31.45% hydrogen chloride work for making aqua regia or should I shop around for a 50% ratio? If it works then what mix, a 4 to 1 ratio or more? Thanks in advance.

 

[NobleMetalWorks]

That's about the highest you are going to find!

Muriatic acid is the same as Hydrochloric acid, Muriatic is just it's industrial use name.

Scott

 

[RESET]

gobot, if you searched for the other several times that the ratio for Aqua Regia has been asked, you would see that it is usually recommended that you don't premix. Add the needed amount of HCl your metal then add Nitric in small increments allowing the reaction to complete before adding more. This way you don't have excess nitric to have to remove after dissolving the metal

 

[NobleMetalWorks]

RESET Is correct. If you were making Aqua Regia to clean with, then you might follow exact measurements to achieve what could be called an Aqua Regia solution. However for our purposes here, most people do exactly what RESET has suggested. We add HCl to water (remember always add acid to water, not water to acid) then make small additions of Nitric Acid and wait for the reaction to finish before adding more. Nitric Acid is expensive, so using more than what is necessary can be expensive, not to mention that when you attempt to precipitate your values, NOx will be created, burning off excess Nitric Acid. It's common for people who have added too much Nitric Acid, to then add far too much SMB so that alter they have to heat their solution again to dissolve the excess SMB into solution, otherwise you get a fine white powder along with your values.

This type of chemistry is all about observation. Make small additions then observe, then make needed additions until all your values are digested into solution. In this way you use only as much Nitric Acid as is needed and don't waste acid or SMB.

Another side note. You should, as a rule of thumb, only require to use as much SMB as Au you are expecting to precipitate.

Scott