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New "acid" to remove calcite from specimens

Posted by Rory Howell  
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Rory Howell May 14, 2009 06:50PM
I have been cleaning some specimens collected this winter - most are either scarn minerals in vugs that are filled with calcite, or magnetite, sphene, apatite, etc covered by calcite. The scarn minerals are usually not affected by hydrochloric or other acids that will remove calcite, but the minerals in the magnetite are - hydrochloric frequrently turns the apatites and scapolites to piles of "sand".

Looking for other ways to remove calcite and save the minerals, I have found a new "synthetic acid" that works great! The material is called EMS Barracuda Concrete Stripper, and is manufactured by Environmental Manufacturing Solutions. The material is very safe to handle, and the MSDS sheet lists it as 000 (non reactive, non corrosive, non flammable).

The material is an amber liquid, and has a slight "soapy" smell, but no fumes of any kind. It is safe on all metal I have tried it on, all clothes I have tried it on, and on counters, floors, etc. (tile grout would be affected though as it is basically calcite with sand). It is safe to handle - the only thing I noticed was a scratch I had from a rose bush stung slightly when my arm was in the liquid. As with all liquids and chemicals, I wear goggles, and if you were inclined to drink the stuff for some reason, the MSDS says that it may cause "loose bowels".

The barracuda dissolves more calcite per gallon than hydrochloric (but slower), and is much safer than any other way I have found to remove calcite chemically. When dissolving the calcite, it causes a very fine "foam" on the calcite as it dissolves. Like dish detergent, it causes a "foam cap", so you have to be careful to leave enough room in the bucket above the liquid level (it did clean all the dirt off my floor in the laundry room real good!). No fumes, no worrys about burns, etc. It did still affect the apatite and scapolite, but mostly just the luster - it did not turn them to "sand" like other acids have.

Unfortunately, the material did not do squat on removal of iron staining on any of the specimens I tried it on, so I am stuck with more aggresive chemicals for that.

I found the barracuda at a local concrete supply store - he had it in 250 gallon totes, but allowed me to buy 5 gallons at a time - cost was only slightly higher than hydrochloric adic would have been.
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alan ions May 23, 2009 11:30PM
Hi,
i've personally found that a good automotive rust remover will get rid iron staining, but don't use it on soft minerals like malachite or azurite.
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Anonymous User May 24, 2009 11:43AM
Rory,

Thanks for the information!!

Philippe.
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Jamison K Turnbull May 24, 2009 12:38PM
I have never use acid to remove minerals from minerals, so I have a silly question, something I hav´nt seen on this site yet. Do you have a before and after picture of the acid bath pieces. I'd like to see how much calcite is removed from a piece and what it looks like "cleaned".
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Anonymous User May 24, 2009 12:52PM
Generally, the calcite to be removed is a main mineral in the vein, and is late-stage. It covers/surrounds all minerals that were formed before it - these that we want to expose. Take for example, http://www.mindat.org/photo-227275.html . Before acid, it was just anhedral white calcite on matrix, with crystals only visible on edges. Now the calcite is removed and it is much more interesting!

Also another example is http://www.mindat.org/photo-227271.html and http://www.mindat.org/photo-227272.html
These were on the same specimen, a large ~40 cm piece of host rock with much calcite. After HCl, I got about 5 specimens and the rest had nothing good. Before HCl, simply a big piece of calcite+rock with a bit of schorl, pyrite.

So I don't have before-after photos, but you can imagine how much calcite is removed - anywhere from 2 cm thick to 20 cm + Just depends on the vein size and how much calcite was kept on the specimen when it was removed.

Philippe.
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Gord Howe May 24, 2009 01:48PM
I have used ordinary pickling vinegar to disslove calcite with good results. It is slow and relatively expensive but it does work. I cannot speak on its effect on scapolite or apatite, but it doesn't bother the other skarn minerals (garnet, epidote, diopside,magnetite,cobaltite....).Best of all it is readily available at almost any grocery store. I will definetly check out Barracuda,though.


Gord
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Mark D. Sherwood May 24, 2009 02:07PM
The EMS Barracuda Concrete Stripper sounds very useful, but my experience as an industrial chemist and hazardous material technician has made me skeptical of product claims. The term "synthetic acid" sounds like it was written by an advertising agency. All materials can be either "natural" or "synthetic." The actual active ingredients are non-disclosed on the MSDS as a patented product and no really useful information is present as to what it is and how it works. History is full of examples of materials that were once thought to be harmless, but later were found to have insidious hazards. Having said that, anything that is more effective and less hazardous than hydrochloric acid is bound to be useful. The fact that this product is being marketed to remove concrete build-up on concrete trucks is significant. I intend to try it, but using precautions that should be used with any active chemical

Avoid skin contact.
Use in a well ventilated area.
Try a small sample or hidden corner for possible unintended effects before treating a valuable specimen.

Mark
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Robert Simonoff May 25, 2009 12:36AM
Chemically "synthetic acid" doesn't make sense. Whether HCl, for example, is created by man or nature, it will have the same effect. Same with Sulfuric acid. Its just not making sense.
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Henry Barwood May 25, 2009 04:53PM
I looked up the MSDS on this product, and the composition is blocked as being a trade secret. It does appear to be organic based from the cited specifications. I normally use acetic acid to dissolve calcite so I can save things like apatite. Would be interesting to test this versus HOAC.

Henry Barwood
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Henry Barwood July 09, 2009 07:21PM
Is there a place to obtain this cleaner here in the US?

Henry Barwood
Troy University
Troy, Alabama USA
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David Von Bargen July 09, 2009 07:53PM
Don't know if they take a drum and break it down or if it is packaged by the pail.
They sell this stuff by 5 gallons:
http://orders.jpsupply.com/webapp/catalog/product/list.asp?line=B0012&C=CTW

Also http://www.enviromfg.com/howto.html has dealer lists for this.
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Henry Barwood July 10, 2009 03:22PM
David,

Thanks for the information. I may have to accumulate a few specimens to warrant even a 5 Gal. pail.

Henry Barwood
Troy University
Troy, Alabama USA
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David Von Bargen July 10, 2009 03:31PM
You might want to call up their tech support line. You might be able to finagle some samples for testing purposes.
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Need to Know July 13, 2009 11:41PM
what is the definition of "Scarn" please?
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David Von Bargen July 13, 2009 11:46PM
A skarn is a contact metamorphic rock developed when magma intrudes a dirty limestone (typically). Minerals such as grossular, epidote, wollastonite etc. are formed by the heat and fluids from the magma.
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Costas Constantinides July 19, 2009 07:37AM
Hello,,Found a product in Australia that sounds similar to your Barracuda Concrete Cleaner only it was callel Barrell Clean Safe(as in concrete truck barrel cleaner) .Of course it came with the msds data etc but with secret ingredients etc..I suspect it is the same product but packaged and named differently..It was a light yellow color,no smell,similar to the description of Barracuda..I tried it on a specimen that i usually use acetic acid on..It ripped the calcite off quickly ,damaged the apatite but left monazite in good condition..I will stick to acetic from now on as a lot of our material in calcite can have Apatite,Garnet,etc Con



Edited 1 time(s). Last edit at 07/20/2009 01:54AM by Costas Constantinides.
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Peter Haas August 08, 2009 10:40AM
Probably a poly(ethylene imine) derivative.
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Georg Graf August 08, 2009 03:51PM
Hi Jamison, hi All,

to remove Calcite I use Essigessenz = pure acetic acid, which you can buy in Germany in each supermarket in the "Spice" department (besides vine gear, olive oil, salt e.c.t.)

It is easy to handle, not very dangerous - don´t bring it in Your eyes! It is an acid!

And the generated Calcium-Acetate is soluble in water. You wash after cleaning Your spezimen in pure water and the acid and the Ca-Acetate is away.. Minerals like Apatite or Fluorite are not attacked, if You don´t let Your spezimen stay a long time in the acid.

I let normaly a small rest of the calcite on the spezimen, so You can see: Calcite was removed by acid.

Other carbonate minerals like Malachite, Dolomite and others are attacked or not, so You have no clear result. Normaly the are not totaly removed, but damaged.

Aragonite reacts with acetic acid like Calcite.

My Pyrochlore of the Kaiserstuhl (...photo-39996.html) was liberated from Calcite by acetic acid. Below the Pyrochlore You can see, unfortunately not sharp - an Apatite prism.

Greetings from Goslar

Georg
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Georg Graf August 09, 2009 09:57AM
Hi Jamison, hi All,

little bit more precise: Essigessenz is pur, 25%, acetig acid.

Greetings from Goslar

Georg
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Ed Drown August 10, 2009 08:24PM
Hi,

It seems that the "synthetic acid" is urea hydrochloride, as disclosed in a patent-infringement lawsuit filed by Peach State Labs against Environmental Manufacturing Systems.

(US District Court for the Northern District of Georgia, Rome Division; Filed Nov 26, 2008)

The disputed US patent is 5,672,279; "Method for Using Urea Hydrochloride".

The patent is fairly straightforward (for patents, that is) in describing how to prepare and use urea hydrochloride for the removal of calcium carbonate.

Ed
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Phillip Peurasaari August 29, 2009 10:52AM
I was able to find a product called Barracuda 10k which is the same as Barracuda concrete stripper just faster working. 25% faster.
I used it to clean quite a few copper pieces from Keweenaw and it worked great. Except for one piece. It turned dendrite copper crystals gold toned. It looks beautiful but why would that happen? I was thinking may be the dendrite crystals have silver or another mineral that reacted with the barracuda 10k? Anyone ever have experience with this stuff?
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horsecore August 31, 2009 03:09AM
Hi Phillip,

Does the Barracuda product indicate what it is, specifically what type of acid, i.e. sulfamic acid or muriatic acid?

In my limited experience with cleaning copper with acids, it seems if you leave the specimen in the acid to long it can discolor the piece. Also, once the piece is removed from the acid, rinse it thoroughly with water and once rinsed towel dry followed by a hair dryer - be sure to remove all water as any remaining water seems to tarnish the piece.

Also, one trick is to soak the specimen in water after the acid bath - it helps take away the "new penny" shine that comes with acid cleaned copper. The length of soak time is strictly based on your taste.

I must compliment you on that Central piece you found in the stream - gorgeous! Any chance that piece is available?

Hope this helps a bit!

Ben
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Ben Vone August 31, 2009 03:19AM
Should have registered before posting (the post from horsecore is my post).

Feel free to drop me an e-mail Patrick - I always enjoy making contact with fellow Copper Country enthusiasts!

Ben

horsecore Wrote:
-------------------------------------------------------
> Hi Phillip,
>
> Does the Barracuda product indicate what it is,
> specifically what type of acid, i.e. sulfamic acid
> or muriatic acid?
>
> In my limited experience with cleaning copper with
> acids, it seems if you leave the specimen in the
> acid to long it can discolor the piece. Also,
> once the piece is removed from the acid, rinse it
> thoroughly with water and once rinsed towel dry
> followed by a hair dryer - be sure to remove all
> water as any remaining water seems to tarnish the
> piece.
>
> Also, one trick is to soak the specimen in water
> after the acid bath - it helps take away the "new
> penny" shine that comes with acid cleaned copper.
> The length of soak time is strictly based on your
> taste.
>
> I must compliment you on that Central piece you
> found in the stream - gorgeous! Any chance that
> piece is available?
>
> Hope this helps a bit!
>
> Ben
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Phillip Peurasaari August 31, 2009 09:10AM
The barracuda k10 product I used is a synthetic acid, the formula is patented and no information is available on it. It does have a 000 health rating on it, but they say to not drink it as it may cause loose bowels. It is kosher too. It works great for cleaning minerals, I plan to post before and after pictures as soon as I return from a trip to Drummond Island, Michigan. I'm hoping to find some nice fossils at Marble Head and the Fossil Ledges. As far as that Central copper piece- it's not available. It belongs to my wife, I give her all my good finds, mostly because I don't want to sell or trade them, if they belong to her I'm not allowed to do so. I've talked to a professor at MTU and he recommends searching the same area for similar pieces, so next year I'll be hopefully finding some more crystals like those. Be looking next week for my before and after cleaning pictures this weekend, I'll use hydrochloric acid, soap and water, and Barracuda K10 for everyone to compare the results.
Phillip
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Jolyon & Katya Ralph August 31, 2009 12:17PM
>The barracuda k10 product I used is a synthetic acid, the formula is patented and no information is available on it.

This makes no sense. If it is patented then the information must be available publically in the patent application documentation, and will probably be online. The whole point of patents is that you can't keep your invention secret.

If it's just a "trade secret" rather than a patent then there's no reason someone can't test it to find out what it is.

In any case I wouldn't suggest anyone put good mineral specimens into an unknown mixture of chemicals.

Jolyon
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David Von Bargen August 31, 2009 01:20PM
They are getting sued for patent infringement for using urea hydrochloride (or some equivalent).

http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=5672279.PN.&OS=PN/5672279&RS=PN/5672279
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Peter Haas September 01, 2009 07:24PM
What is "urea hydrochloride" ?

This is replacing a trade name with a trivial name that doesn't make any sense either ....
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Knut Eldjarn September 01, 2009 08:51PM
According to the filed patent it is just a mixture of urea and hydrochlorid acid. The branded products refered to probably also have surfactants or other components added. I would personally not risk trying such a mixture on specimens with minerals known to be soluble in hydrochloric acid (like apatite, tephroite, trimerite etc.) In such cases I will stich to acetic acid as described by others.
Knut
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Peter Haas September 02, 2009 01:09PM
Well, if you mix urea with hydrochloric acid, you'll end up with ammonium chloride.
Urea will not survive being brought in contact with mineral acids in any conditions. It even hydrolyses in demineralized water; reaction will be complete within a couple of minutes at less than 60 °C. Acids considerably accelerate decomposition (H+ catalysis).
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Alfredo Petrov September 02, 2009 01:20PM
Peter, would calcite be soluble in ammonium chloride solution? Or is the patent application simply not telling the truth about the ingredients? (which would sort of miss the whole point of making a patent application)
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Howard Heitner September 10, 2009 03:15AM
Urea hydrochloride seems to be stable enough to have a CAS # (506-89-8), and to be offered for sale by a number of companies. Example 1 in US Patent 5,672,279 gives a fairly detailed description of how to make it. The patent states that there is a slight exotherm, when the reactants are mixed. The only detail that is omitted is the maximum temperature that the mixture can be allowed to reach, before the urea starts to hydrolyze. . This may seem to be a minor detail, but when a reaction is done on a large scale, it is very important. Based on my years of experience in the chemical industry, there is a finite possibility the the procedure described in the the patent is total bogus, however if another company was able to infringe the patent, it is probably fairly accurate.
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Alfredo Petrov September 10, 2009 06:18AM
So, in removing calcite, what's the advantage of urea hydrochloride over plain old dilute HCl? Considering that HCL is very cheap and very widely available, why switch?
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Howard Heitner September 11, 2009 12:39AM
The chief disadvantage of hydrochloric acid is the corrosive gas that the aqueous solution gives off. This can cause severe damage to to the lungs and will also corrode any metal it contacts. These other acidic solutions do not have this problem. The weaker acids may also not react with some other minerals, such as sulfides and some silicates, which are attacked by hydrochloric acid.
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Alfredo Petrov September 12, 2009 06:25AM
A trick I learned from Rock Currier was to use nitric acid when taking carbonates off of sensitive silicates, like dioptase and inesite - Nitric doesn't hurt most slicates anywhere near as much as HCl does.

Nitric acid however should never be used for cleaning sulphides. Dilute HCl works fine on most sulphides. Almost all the abundant pyrite and sphalerite specimens from Peru on the market have been cleaned with HCl and, contrary to many peoples' expectations, the pyrite remains stable; the HCl does not cause it to decompose.



Edited 1 time(s). Last edit at 09/12/2009 06:30AM by Alfredo Petrov.
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Bill Browne September 28, 2009 04:15PM
Rory:

EMS does make a product that is very effective on rust stains.
It is called Players Choice. The link is:

http://www.enviromfg.com/pdf/Groundskeeper%20Literature.pdf

I suggest you try it.
EMS has over 100 products and can make custom formulations to meet a wide array of needs. We have used a number of them with great success. And they are totally GREEN.
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jmac October 21, 2009 07:27PM
Ed Drown and all others,

Please see attached. One must know how to read a civil filing prior to passing judgment.

PSL "accused" EMS of this and never tested Barracuda nor did they ever make Barracuda or any of the other accuse products for EMS. This case was dismissed after investigation, depositions and a strong 40+ page order from the judge in Rome Georgia.

Our formula for Barracuda and many other products have been tested by NSF, certified as DfE worthy, have been evaluated by FDA experts and such. I can go one and one with valid governmental documentation such as a 96 page test from the US Department of Navy.

EMS has since file against PSL for patent invalidity. EMS sells in BULK thus I realize none of you would be paying customers however, if anyone wants a FREE sample of our Barracuda; please email me direct at jmac@enviromfg.com.

Thanks
open | download - DOC.PDF (54.7 KB)
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Ed Drown October 26, 2009 05:12PM
"jmac"

Apologies for not responding sooner, it is good when a representative (I presume) for a company can answer questions about the use of their products. With regards to the documents referenced herein, they were located via a Google(TM) search and are believed to be but not necessarily represented as true copies.

coby.nixon.googlepages.com/PeachStateComplaint.pdf
shumakerindustries.com/pdf/Barracuda Literature.pdf

The filing by Peach State Labs, "PeachStateComplaint", dated November 26, 2008 is fairly clear. Bully for you in getting a dismissal. I do not recall, however, any assertions made in this forum as to the validity of PSL's claims. In their filing PSL did disclose their patent and therefore their active ingredient(s); which was germane to the topic under discussion, i.e. what type of "acid" is in "Barracuda". That question was not definitively answered in the PSL filing. It does appear, however, that they believed it to be urea hydrochloride.

It is all well and good for you to have NSF and FDA approvals for "Barracuda", do you have any documents from the US patent office (or WPO) that you can cite? The above referenced version of your product literature does have on its first page the claim that you have patented this "acid," quoting:

"Independent tests confirm that Barracuda, formed with EMS’ patented SynTech®, the world’s only synthetic acid, dissolves nearly 15% more concrete than Hydrochloric acid."

Which patent(s) covers "SynTech®"?

It seems to me that in this forum, marketing terms will not get one very far in having your product accepted by all as suitable for mineral cleaning and preparation. The statement in your brochure "It is safe on paint, chrome, aluminum, wiring, plastic and even glass." does not begin to cover the diverse chemistry that is encountered in this field. If your "synthetic acid" contains chloride ions, those that wish to use it to clean native copper for example, would want to take that into consideration when determining its suitability for use.

That is why the composition of "Barracuda" was and still is it seems, an open question and a concern to those who may wish to try it.

Any clarification that you can provide would be greatly appreciated.

Cheers,


Ed


Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement or recommendation. Product names are for identification purposes only. All trademarks and registered trademarks are the property of their respective owners.
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Stephen Moreton October 26, 2009 05:36PM
My favourite acid for dissolving carbonate minerals off slightly sensitive minerals, in particular off fluorite and native silver, is phosphoric acid. It is not as hazardous as hydrochloric but the usual precautions should still be taken. Not sure that it would be safe to use on apatite though, danger of soluble calcium hydrogen phosphates forming.
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Peter Haas December 01, 2009 06:56PM
Stephen,

Apart from the solubility of apatite, the conversion grade of phosphate into hydrogen phosphates only depends on proton concentration (i.e. pH value) and acid strength (i.e. pK value), because the reaction is a proton transfer. The chemical nature of the anion has no effect. The risk of apatite decomposition, therefore, is lowest with phosphoric acid (pK1 around 2) and much higher with all other mineral acids (pK < 0).

The most annoying side effects of phosphoric acid are the low solubilities of many phosphates, giving rise to the formation of unwanted precipitates. A good alternative is citric acid, which has a similar strength, but superior complexing ability. Dissolution of calcite by mineral acids acts only on the anion (carbonate decomposition). In citric acid, this is assisted by complexation of the cation.
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Marc Maseman June 30, 2011 08:49PM
If anyone is still interested, the information about the case being dismissed is no longer valid. Peach State has recently won a patent infringement case against EMS for the use of Urea Hydrochloride. Peach State Wins Verdict in EMS Infringement Case.

From the article:

4/19/11 - EMS Willfully Infringes Peach State Labs Patent ROME, GEORGIA (April 19) – A US District Court for Middle District of Florida jury has found that Environmental Manufacturing Solutions (EMS) willfully infringed on Peach State Labs, Inc’s. method for using urea hydrochloride (patent 5,672,279). The jury reached a verdict on Monday, April 18 in the matter which was filed in 2009 -- Environmental Manufacturing Solutions, LLC v. Peach State Labs, Inc., Case No. 6:09-CV-395.

Urea Hydrochloride is a commonly used product for removing mineral scales and for pH control as buffered HCl is safer than HCl. But, please don't confuse "safer" with "safe". Many of the companies blending Urea HCl in violation of Peach State's patent do not blend at the recommended level of at least one part urea to one part HCl to make a complete buffer. Typically, with concrete removers, a 1:1 buffer doesn't work very well, so most companies use .5 part Urea to 1 Part HCl, leaving half the acid content as free HCl. This will knock down the fuming action, but by no means makes it safe.

I have personally witnessed many chemical burns and lots of damaged equipment from the use of Urea HCl and the many products in the market that claim 0-0-0 using Urea Hydrochloride.

For a good test of your 0-0-0 "synthetic" or "safe" product, take a pop top from a soda can and drop it in to a sample. Urea HCl will completely dissolve the aluminum top within a half a day. And by completely, I mean it will be gone. One comment was correct that "synthetic" etc is a bunch of marketing hype. All the "patented" language from EMS is based on Peach State's patent in which they are in which they now have been judged to have infringed upon. To my knowledge, EMS owns no patents of its own.

No one will tell you what is in their safe product, so it is up to you to either demand empirical evidence from a third party laboratory (and that you trust the results to be valid) and that you do some homework on your own. As you may be able to tell, I am in the industry and compete against EMS. We battle with marketing half-truths and deceptions daily.

This was written to help shed a bit of light on the subject and not for the sake of mentioning my product, but since I am here, I can also say that we offer lines of products that are truly safe..



Edited 1 time(s). Last edit at 06/30/2011 11:40PM by Jolyon Ralph.
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Peter Haas June 30, 2011 10:07PM
I'm not inferring that the product doen't exist - it only has not much to do with what the name implies. In particular, it is not a hydrochloride - much in the same way as "thiurea dioxide" (another entirely misleading trivial name) has not much to do with waht the name implies but is a sulfenic acid derivative instead. Trade names, however, are often just conceived for obscurification.
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Tom Trebisky June 30, 2011 11:30PM
The label "synthetic acid" is a pretty silly term. In general, good old hydrochloric (muriatic) acid is a synthetic acid.
The only "natural" way to get hydrochloric acid that I can think of would be to pump somebody's stomach.
The usual marketing hype I suppose, insofar as calling something a synthetic acid would add to the products
appeal. I would still be careful with it, as has been said. For that matter I would be careful with acetic acid,
which is quite "natural"
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George Balogh July 01, 2011 02:10AM
Hello,

Interesting this thread is running. I am about to post a new thread regarding acid etching.

Many in the Copper Country of Michigan use sulfamic acid, sold in hardware and home improvement stores as a solid that can be dissolved in water. It is faster than vinegar. That said I like vinegar. It is gentle and slow and if followed by generous and repeated soakings in water crystals of many minerals come out clean and not frosted. Sulfamic seems to clean copper and silver well but accessory minerals may not survive as well.

George
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Ed Godsey July 25, 2011 01:05AM
Georg Graf Wrote:
-------------------------------------------------------

>
> little bit more precise: Essigessenz is pur, 25%,
> acetig acid.
>
I too used to use Essigessenz for calcite removal. But I found a much cheaper 25% acetic acid source at the local Korean market. It's in a liter size bottle and called simply 'concentrated vinegar' in English. It's less than $4.00 and and will dissolve a lot of calcite.

I first came across it searching for a safe weed killer, which it is when diluted 2:1. Blackberries are a noxious weed here and I use it so I don't incur the wrath of the park district which has the adjoining property.

Easy Goin'
USA
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Bart Cannon July 31, 2011 02:37PM
Don't all strong acids get their mineral dissolution job done the same way regardless of dilution of the acid component ?

My haphazard experiments with acids and minerals over the years have produced many curious results which lead me to believe that a crucial factor is the composition of the solution as the reaction occurs.

For example, when dissolving calcite away from pyrrhotite, things work well for a while, and then suddenly, the acid bath starts generating hydrogen sulfide and the the pyrrhotite starts dissolving. I think that this is because the HCl solution has become a CaCl2 solution which must be corrosive toward pyrrhotite.

Here in King County, Washington we have wonderful locality for shiny dodecahedral magnetite enclosed in calcite. The darned things are always etched when I use HCl to remove the calcite. Maybe magnetite is soluble in a CaCl2 solution resulting from the interaction of calcite with HCl.

I'm going to try some other acids, including this now infamous "synthetic" acid.

Since we have all these chemists on this thread, I will impose upon them to explain why ammonium bifluoride is a more pleasant, yet effective substance to use for opaline crust removal on other silicates than even dilute HF. Doesn't it dissociate into the same thing?

I've heard some talk that I don't understand about ammonium bifluoride being "self buffering". Maybe that means that it's always just the right concentration. Magic?
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roberto sbalchiero August 10, 2011 11:32AM
Hallo, have someone try the Barracuda on Natrolite or other zeolites? Whith Hcl you get a silica gel .
Thanks.
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AngryAngler17 August 24, 2011 02:08PM
Marc,

Does your company sell urea hydrochoride? I think a lot of people on here were just looking to purchase it and try it out. In light of what you've posted some of us may be swayed away from ordering barracuda.Thanks
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Wallace Mitchell May 15, 2012 05:57PM
Rory,
I would like to reestablish contact with you.

Wallace
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