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Thread: Making aqua regia

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    Making aqua regia

    Anyone have experience of doing this?

    Aqua regia or aqua regis (Latin for royal water or king's water) is a highly corrosive, fuming yellow or red solution, also called nitro-hydrochloric acid. The mixture is formed by freshly mixing concentrated nitric acid and concentrated hydrochloric acid, usually in a volumetric ratio of 1:3 respectively. It was named so because it can dissolve the so-called "royal metals," or noble metals, gold and platinum.
    I can get hold of the acids, but I've been reading that the 1:3 ratio isn't as straightforward as it seems, as we're talking moles rather than volume (contrary to what the wiki entry quoted above says). Given that my chemistry knowledge is distinctly lacking, I'm hoping someone can offer useful advice as to the production of aqua regia.

    (to the curious, basically I'm thinking of doing this because I can buy 20ml of pre-mixed aqua regia for about £25, and I can buy 2.5 liters of hydrochloric acid and 2.5 liters of nitric acid for about £50, and paying 250 times the cost of the constituent parts just peeves me :boom)
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    Re: Making aqua regia

    You don't say what country you are in. In the USA you can get hydrochloric acid at any hardware store for $7 a gallon, roughly $1.75 per liter. Nitric acid comes from the gardening supply store labeled as stump remover (potassium nitrate).

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    Iridium mamboni's Avatar
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    Re: Making aqua regia

    Quote Originally Posted by uranian
    Anyone have experience of doing this?

    Aqua regia or aqua regis (Latin for royal water or king's water) is a highly corrosive, fuming yellow or red solution, also called nitro-hydrochloric acid. The mixture is formed by freshly mixing concentrated nitric acid and concentrated hydrochloric acid, usually in a volumetric ratio of 1:3 respectively. It was named so because it can dissolve the so-called "royal metals," or noble metals, gold and platinum.
    I can get hold of the acids, but I've been reading that the 1:3 ratio isn't as straightforward as it seems, as we're talking moles rather than volume (contrary to what the wiki entry quoted above says). Given that my chemistry knowledge is distinctly lacking, I'm hoping someone can offer useful advice as to the production of aqua regia.

    (to the curious, basically I'm thinking of doing this because I can buy 20ml of pre-mixed aqua regia for about £25, and I can buy 2.5 liters of hydrochloric acid and 2.5 liters of nitric acid for about £50, and paying 250 times the cost of the constituent parts just peeves me :boom)
    Please be extremely careful with this stuff, or you will experience that scene in Alien when the crew tried to cut through the parasite attached to William Hurt's face.
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    Re: Making aqua regia

    Quote Originally Posted by Saul Mine
    You don't say what country you are in. In the USA you can get hydrochloric acid at any hardware store for $7 a gallon, roughly $1.75 per liter. Nitric acid comes from the gardening supply store labeled as stump remover (potassium nitrate).
    Isn't the hydrochloric acid actually muriatic acid? This is not 100% HCL. It is pretty dliute. You should use laboratory or at least industrial grade chemicals. You should also have proper facilities, protective equipment, and some training before playing with concentrated acids.

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    Iridium mamboni's Avatar
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    Re: Making aqua regia

    Quote Originally Posted by JohnQPublic
    Quote Originally Posted by Saul Mine
    You don't say what country you are in. In the USA you can get hydrochloric acid at any hardware store for $7 a gallon, roughly $1.75 per liter. Nitric acid comes from the gardening supply store labeled as stump remover (potassium nitrate).
    Isn't the hydrochloric acid actually muriatic acid? This is not 100% HCL. It is pretty dliute. You should use laboratory or at least industrial grade chemicals. You should also have proper facilities, protective equipment, and some training before playing with concentrated acids.
    Yes, one must use fuming HCl and Nitric.
    Tricks and treachery are the practice of fools, that don't have brains enough to be honest. -Benjamin Franklin
    Sincerity makes the very least person to be of more value than the most talented hypocrite. -Charles Spurgeon

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    Re: Making aqua regia

    I love aqua regia - to me there's just something fascinating about being able to dissolve gold into this "royal water". I always thought the perfect crime would be to get a job at the mint where you have access to all the gold, somehow line a thermos with something so it could hold some of the aqua regia, bring your thermos to work in your lunch box, sneak some gold blanks in the thermos and leave with no one the wiser. Ha ha, of course I would never do this, nor have I ever held a job at the mint, although it might be fun...

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    Re: Making aqua regia

    I'm in the UK. 70% pure nitric acid is available for £25 (2.5 liters), approx. 40% pure (beyond this apparently it just evaporates too quickly to be of practical use) hydrochloric acid for £18 (2.5 liters).

    Mamboni, thanks for your concern. I've been talking to the guy at reagent (the shop in the UK) and he's been trying to put me off buying the acids to mix myself too (he was slightly relieved to hear that I have a decent air filter I think!). I shall attempt to not replicate Hurt's face. I do understand that these are dangerous chemicals, as I've been using premixed aqua regia for a while now. I know that the mixture will fume as it's being mixed. I also know that a fair few jewellers will give their AR a whiff before use to see if it's fresh (on the basis that if they start coughing, it's fresh), though I tend not to do that myself!

    No thoughts on the ratio of the acids? I did come across this thread in the gold refining forum, which suggests the following mix for testing 18 carat gold:

    5.9 mL nitric - 5.9mL distilled water - 17.8 mL hydrochloric
    so I'm thinking that it is just a simple 3:1 volume mix of the 2 acids. Certainly with 2.5 liters of each acid I'll have enough to last me a lifetime, that's the smallest size that reagent sell.
    Be kind, for everyone you meet is fighting a hard battle.

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    Re: Making aqua regia

    an interesting question, but my use for aqua regia is to test gold, rather than dissolve bucket fulls of the stuff!
    Be kind, for everyone you meet is fighting a hard battle.

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    Re: Making aqua regia

    Quote Originally Posted by mamboni
    Quote Originally Posted by JohnQPublic
    Quote Originally Posted by Saul Mine
    You don't say what country you are in. In the USA you can get hydrochloric acid at any hardware store for $7 a gallon, roughly $1.75 per liter. Nitric acid comes from the gardening supply store labeled as stump remover (potassium nitrate).
    Isn't the hydrochloric acid actually muriatic acid? This is not 100% HCL. It is pretty dliute. You should use laboratory or at least industrial grade chemicals. You should also have proper facilities, protective equipment, and some training before playing with concentrated acids.
    Yes, one must use fuming HCl and Nitric.
    Baloney. Aqua regia forms naturally from nitrates in the soil and acids in rain. The product is good enough to dissolve gold in streams (even while the water is still safe to drink) and has long been a pesky nuisance to gold miners.

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    Re: Making aqua regia

    Quote Originally Posted by madfranks
    I love aqua regia - to me there's just something fascinating about being able to dissolve gold into this "royal water". I always thought the perfect crime would be to get a job at the mint where you have access to all the gold, somehow line a thermos with something so it could hold some of the aqua regia, bring your thermos to work in your lunch box, sneak some gold blanks in the thermos and leave with no one the wiser. Ha ha, of course I would never do this, nor have I ever held a job at the mint, although it might be fun...
    mining gold is mining gold, it's legal.

    but if you're gonna have that solution in a thermos you'd better have a bunch of safety stuff, safety glasses etc.
    i smell bagels.

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