Nitric acid-testing for gold

Hi,
If anyone could assist me it would be greatly appreciated. I use nitric acid to test for gold purity (to determining the karat value of gold). The acid comes in a small plastic bottle containing ½ fl once of acid. Only one drop comes out of the bottle at a time. The odor even in this small amount is not pleasant. What is the health hazard? Is there anything that I can practically do to protect myself from inhaling the fumes? I currently use a small desk top fan to disperse the concentration of the fumes that are rising in my direction. Would a simple 25 cent disposable mask that is used to prevent the inhalation of dust have any effect? Please keep in mind that I am checking the gold at “gold parties”. I can’t come out in a space uniform 
Thank you,
RC


rusticrick's picture

nitric

welcome to forum. nitric is not dangerous, more like hazardous

http://www.cdc.gov/niosh/npg/npgd0447.html

Relative health hazard
On a health hazard spectrum of 0 - 3 Nitric acid registers 1.8. A score of 3 represents a very high hazard to health, 2 represents a medium hazard and 1 is harmful to health. . A substance that scores highly as a health hazard is arsenic at 2.3 and one of the lowest scores is ammonia at 1.0.

on the mask,I would want something with activated charcoal

rick


rc's picture

Nitric acid for testing gold

RC

Thank you! any idea where I can purchase the mask that you described?


rusticrick's picture

mask

I think I saw some at a paint store or maybe auto paint store

iron is just unfinished rust


Dick C's picture

If a charcoal filter will

If a charcoal filter will help, you might try a soldering station fume extractor. Here's one at Amazon: http://www.amazon.com/Xytronic-426DLX-Fume-Extractor/dp/B0007ZLH4Q  It's not one I've seen before, but it's small and inexpensive. A search for "fume extractor" will turn up more of them.


Rich Waugh's picture

I'm surprised that you are

I'm surprised that you are ausing nitric acid to test gold purity. The standard test for gold purity always used to be using standard needles on a granite slab and etching using aqua regia, not straight nitric acid. Aqua regia is a mixture of nitric acid (HNO3)and hydrochloric acid (HCl). The chlorine aspect of the HCl is the more toxic of the ingredients.

A particle mask or a charcoal filter mask will do nothing to protect you from the vapors of aqua regia. You will need a filter cartridge that is rated for organic vapors including acids, such as the 3M filter #6002, or better. There is little likelihood of real damage with only one drop of acid vaporizing, however, provided you have reasonable ventilation. Since I don't know what a "Gold Party" is, I have no way of knowing whether you're trading gold jewelry or huffing gold paint, so I won't offer any suggestions for that.


visitor's picture

testing gold

where can you buy the ntric and hydrochloric acid?


Rich Waugh's picture

Hydrochloric acid is sold at

Hydrochloric acid is sold at hardware and pool supply stores as "Muriatic Acid" - it is about 35% dilution. For concentrated HCl and Nitric Acid (HNO3), check Van Watrers & Rogers or other chemical supply houses. These concentrated acids are quite dangerous if you don't know what you're doing with them, however. I would think that you could get ready-made Aqua Regia from Rio Grande Jewelery Supply or Santa Fe Jewelers Supply.


visitor's picture

Aqua Regia shelf life

Aqua regia will only last a month at the most.... Its not very difficult to make.... just read up as much as you can or maybe take a course.... nitric acid is a lot easier for this reason... but i have been getting interested in the schewter salts.... they seem to be the way to go but i need to do more research.... also nitric acid is very explosive! i would not worry about inhaling the fumes as much as blowing up an entire building! be very careful with nitric acid! keep it stored in a colder climate and never ever heat it!


Rich Waugh's picture

Nitric acid is not, in

Nitric acid is not, in itself, explosive. It is, however, an extremely active oxidizer and will make other substances explosive if it comes into contact with them. Furthermore, nitric acid has the potential for highly exothermic (heat producing) reactions with a variety of substances. Nitric acid can be stored at room temperature perfectly safely, provided that it is kept in an air-tight container and is not allowed to become contaminated with anything.

Nitric acid fumes will destroy the mucosa in your lungs almost instantly, resulting in death from drowning inyour own fluids. Further, the fumes from nitric acid attacking metals can be anything from noxious to the deadly brown nitrous oxide. Do not take the fumes lightly if you wish to remain healthy.

Just setting the record straight. As with any chemical or potentially dangerous substance, the user is advised to seek all the available facts and determine for himself how to proceed safely.

Rich Waugh


visitor's picture

schwerter salt or solution

My name is Al and I wold like to know if you have found more information about using schwerter solution for gold testing. The reason being I am about to buy nitric acid for gold testing. I know it is dangerous but I intend to hold my noes or something. I hope you have time to reply to my inquirey. Al e-mail me at al4030@hotmail.com


visitor's picture

Stainless Steel >>> Fake white gold

Apparently a group in the Phoenix area & AZ & other SW states are selling white gold which is actually stainless steel. A precious metal buyer payed $500 for a "white gold" bracelet that was stainless steel worth $5.

How can one easily tell the difference ?

TIA
David


visitor's picture

Agua Regia, Gold testing and health hazards

Dear mr. Waugh,

by your answer and photo I concluded you are a trustworthy person. I'm addressing my questions to you because I worrie sick about my husband who has been checking gold after he lost his job in early 09.

What is the health hazard for a 60+ yo parson who checks gold with acids 10 hours a day 5 days a week without a mask in a just ok ventilated room?

is agua regia the only acid used to test gold? If not, what are the others? and where does one can find info about those substances?

Also is the concentration of the HCL increases as the gold content does.

If you don't want to answer all my questions please answer ony the first two; I will greatly appreciate it.

sincerely,
tsr
Boston, MA


Rich Waugh's picture

Without doubt, breathing the

Without doubt, breathing the fumes of aqua regia is not good for you. There is simply no good reason to do this when proper chemical vapor respirators are available from industrial safety supply houses for under fifty bucks.

There are other acids used to test gold, but ANY acid used to test gold will be toxic and noxious.

A proper respirator and adequate ventilation are the only solution, other than avoidance.

I'm over 60 myself and I know we tend to get fatalistic at that age, but that's no excuse for taking unnecessary risks.

Rich


visitor's picture

acid testing gold fumes

I used to do the nitric acid test and get a nosefull of fumes which can cause odema and nasal mucosal lining problems,i now use the nitric on a testing stone after rubbing a strip of gold onto it.I let the fumes go to work and then return to it after about 1 minute,by which time the stong fumes have gone and my nose is safe.If the gold coloured residue is still there it is probably gold.Only problem has been with some of the more exotic white gold metal mixes(fake ones)which will not respond to nitric unless exposed for an extended time period......


visitor's picture

Nitric Acid, Aqua Regia & Gold

You need a "fume hood" and a herpa rated mask and filters. Also I would use a plastic overall and a full face and head covering.

To properly separate/purify gold with HNO3 you have to reduce the gold content to 25% or less by melting in soemthing else, then pouring into water for "flake shot" and then bathing the flakes in nitric acid. By lowering the gold content the nitric is able to remove the impurities, uncovering the gold. The content has to be reduced before nitric extraction, so that less impurity is contained in gold,making it unextractable without AR, and more gold is contained within the impurities (important distinction).

Aqua Regia is relatively inert until metal is added, then it will produce vapors that rust steel within seconds. Not to be used without proper ventilation and shouldn't be near occupied buildings, or near steel roofing, etc.

Strangely enough, immersion in AR doesn't do much to steel. But if it is exposed to the reactive VAPORS it will be oxidized. Use Chemical filters in your mask. This stuff will kill you if you're not carefull. And it's dangerous to anyone within 100 feet.


Rich Waugh's picture

Good points, visitor.

Good points, visitor. However, the mention of a "herpa" (sic) filter for the mask is not correct. I'm assuming, of course, that you meant HEPA filter. A HEPA filter is only for removing particulates down to a certain size, and does nothing at all for toxic vapors. It may have some very slight efficacy for fumes, which tend to be particulates suspended in gas, but I wouldn't take the chance of testing that hypothesis. As you later stated, a proper chemical filter rated for the substance(s) being used is what is needed.

Rich


visitor's picture

This is the simular to the system i use and recon its the best

i take a big breath then breath out very slowly as i do the test then walk away and come back a few minutes later,
a mask creates a false sense of security and can cause more damage


Rich Waugh's picture

If wearing a mask gives you

If wearing a mask gives you a false sense of security then you are not using the proper filters, or don't have the mask fitted properly, or are using expired cartridges, or are using a faulty mask. Holding your breath is NO substitute for a properly fitted respirator with the appropriate cartridges for the hazard(s) present, along with face/eye protection, gloves, apron and any other necessary personal protective equipment (PPE).

While you may be able to hold your breath for a while, can you remember to keep holding it when something dramatic happens or you fall or have some other accident? What about eye protection - are you going to shut your eyes, too?

Proper PPE is not an option, it is a MUST. Life is far too short to spend any of it injured, dead or in jail, to paraphrase an industrial safety expert friend of mine. Looking back on things I did when I was much younger, I am frankly surprised that I am still alive with all my organs, digits and extremities. I was nothing short of fantastically lucky to have gotten away with it. As Moderator of this website, it is incumbent upon me to promote proper, safe work practices and the use of appropriate safety equipment and I will do so at every opportunity - I don't want any of our members or visitors to come to grief.

Wear the right mask, please!

Rich


Moti Lalwani's picture

Thank you Rich waugh!

Thank you Rich waugh!


visitor's picture

Nonreactive White Metals

I have a sterling silver cigarette lighter that's built into a cigarette case. I wondered if the body of this lighter was also sterling. I put a streak on the stone and tried silver testing acid. Instead of disappearing or turning bright red, it stayed bright and shiny. On to 10K acid. The same thing happened. !4K acid--same and 18K as well. The mark finally disappeared with platinum strenth testing acid. What could this white metal be? What metals resist reaction to nitric acid tests besides gold and platinum?


visitor's picture

Nonreactive White Metals

Does anyone know what white metals resist acid up to 18K strength other than gold and platinum? I have a cigarette lighter that stands up to all acid strengths--silver, 10K, 14K, up to 18K when finally the mark on the stone fades. Would such a metal be considered a precious metal?


earthboar jewelry's picture

nitric acid

I assume you were able to satisfactorily solve your problem. I happen to work in applied research so work with strong acids and bases. If you didn't solve your problem - what is the Normality of your solution?

Cathy


visitor's picture

gold testing chemicals and harm

I work for a pawn shop and we are forever testing gold the ventilation is not an issue for us its getting the chemical od your hands. It leaves litlle yellow spots if it makes contact with skin then several days later the skin peels off. Is the chemical dangerous and life threating. I only ask because the new guy is covered in yellow dots not only is it unprofeshinal looking but i had to make him quit doing gold tests because i dont know the danger of skin contact. Any info would help Please reply to dannyboyredneck@yahoo.com. thanks any and all...


visitor's picture

yellow on your skin from acid

latex gloves from Walmart will keep the acid from damaging your skin (yellow spots) and a lab coat or smock will save your cloths. the gold testing acid is not dangerous because of the small quantity of acid. it just gives the skin that unsightly look. i have made holes in a number of my jeans from working with acid in the lab. i found your questions because i was looking for how electronic gold testers function. the price of gold is about sky rocket soon. buy as much as you can and melt it down into ingots yourself. in the depression of the 1930's people holding gold during that time did quite well. because paper assets (paper money) became practically worthless. i learned that when i studied a book "The New Economic Disorder", Larry Bates. if his numbers are right there is a depression coming that will make the the 1930's seem like small potatoes.


Rich Waugh's picture

Latex gloves are only good

Latex gloves are only good for short-term use with dilute acids. Most acids will attack latex given a little time. For real acid-proof gloves you need to order them from a safety supply house - I recommend the gauntlet length ones that also offer some protection for your forearms. Similarly, an acid-proof rubber apron will do the most to save your clothes. Most clothing made from organic materials, (cotton, linen, wool) may look fine right after you finish working with the acid, but after a washing will show numerous holes where the acid attacked them. Been there, done that - too many times.

Rich


visitor's picture

MSDS, anyone?

(not the previous visitor)
When dealing with nasties, take time to read the specific Material Safety Data Sheets for whatever you are working with and any by-products of the reactions it produces or may produce.

For example, Google "MSDS Aqua Regia".


visitor's picture

Some Comments and Questions

First, I would like comment that the moderator of this forum seems very intelligent (although I may not share the same zeal for what I perceive to be slightly excessive safety recommendations; you CAN have too much safety when it starts to take the "fun" out of what you're doing) and that it is rare, unfortunately, that I come across someone who actually seems to know what they're talking about when it comes to "physical science" topics, ESPECIALLY chemistry.

I share the same respect for strong acids but I must say that drop-sized quantities of HNO3/HCl mix would only get regular nitrile gloves and eye protection for short-term use from me. For longer term use (more than a few tests) I would maybe use a lab-coat, long gloves, a fan and goggles. I wouldn't bother with a respirator for small amounts of NO2/HCl/Cl2 vapors floating around UNLESS you are in a small room. Just turn a fan on and keep the door open. Respirators and fume hoods are only necessary when working with larger amounts of these acids (while you're mixing them in slightly larger quantities, do it outside).

Of course, if you don't mind the discomfort and the more than $50 you will likely spend (I haven't even checked but I bet you they are hundreds of dollars at Fisher or Aldrich) then there's nothing wrong with it, in my opinion. I have been around significant quantities of NO2 and I know from experience that it is not as super-toxic as a lot of the "hypers" on the internet want you to believe. Regardless, I suppose safety is never a poor investment... unless you don't have an accident. Just kidding.

Anyway, I have never tested for gold so I just wanted some details on the test. The way I understand is that you rub the substance to be tested on a rock and then attempt to dissolve the streak in increasing concentrations of aqua regia? One of the things that got me interested was when I took a 22k Au coin to a pawn shop and they said that it "tested positive for Pt" so they couldn't buy it from me. I told them that, although I wasn't sure, it might make sense that such a high percentage of Au would test similar to Pt. I don't think he believed me that it was 22k and probably proceeded to test it with 18k "strength" and then the Pt test (and he probably didn't wait long enough). Of course, they were in no mood to listen to any chemistry lectures and their eyes proceeded to glaze over, at which point I proceeded to leave.

Is there something in a typical chemistry lab or at home that I can use that would be appropriate for rubbing the coin on? I can't imagine things like that would be too uncommon. Also, what are the exact concentrations of the acids to be used? And for those that are afraid of using HNO3 directly, why can't a nitrate salt be used?

Thanks!


Rich Waugh's picture

I mostly agree with you on

I mostly agree with you on the safety stuff, but I have to be a little bit stringent since this is viewed by all sorts of people who may know nothing at all - so I err, if at all, on the side of caution. Better safe than sorry, right? (grin)

The customary substrate for testing is a granite slab. Try your local monument (headstone) company for a scrap of black granite. You don't use different concentrations of Aqua Regia - one solution is used for all and you have "standards", gold needles of differing, know gold content. You match the action of AR on your unknown piece with the action of the standards and determine a match in terms of extent of the action of the etchant.

Sounds like the pawn shop was looking for an excuse to drop the price and were waiting for you to offer to accept less money for the coin. .


visitor's picture

gold testing

This is hilarious reading all your comments .....thats the trouble with science ....It puts hazadous items into the hands of incompetent people .Especially funny was the pawnboker story.....does nitric acid damage the skin was the question...it disolves almost all metal and is the main ingredient of gelignite if that helps give you an idea


Pete Crowbaby's picture

gold testing

I found this thred very interesting and not at all "hilarious" and rich waugh advice on acid must be serious as someone who has work with acid in fur dressing, i have seen what can happen. gold has a feel about it, its colour when solid is not the same as when plated. gold is always heavier than ss, gold plated silver, and most other metal. gold is soft and will have little dents and scrachs, feel the metal in your hand is it heavy like gold? has it the same deep lustre all over? rolled gold and some alloys can trick the acid test, don,t wish it to be gold, know it is in mind.