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Rhodium Tests.

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seco

Post September 13th, 2007, 5:55 pm

Rhodium Tests.

I came across a pan load of this silverish-lightbrown reflective material in my gold pan. heavier than the black sand. Im not to sure what it is but I think it might be Rhodium. Would anyone know what i could use to test it? I have found platinum and gold in the same area.
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lazersteve

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Post September 13th, 2007, 6:49 pm

Rhodium Information

Seco,

Welcome to the forum.

I found this info about Rhodium:

Standard Method of Chemical Analysis wrote:Rhodium
DETECTION
Rhodium is found only in platinum ores. It is a white metal, difficultly
fusible, and insoluble in acids. Rhodium, however, dissolves in aqua regia
when alloyed with platinum, to a cherry red solution. It is also soluble in
molten phosphoric acid and dissolves when fused with acid potassium sulphate with
the formation of K3Rh(SO2)3. If the metal is treated with chlorine in the presence of
sodium chloride there forms a soluble salt, Na3RhCl4.
Rhodium monoxide, RhO, is obtained by heating the hydroxide Rh(OII)3,
by cupellation of an alloy of rhodium and lead, or by igniting the finely-divided metal in a
current of air. It is a grey powder with a metallic appearance, and is not attacked by acids,
and when heated in hydrogen is reduced with evolution of light.
The oxide, Rh203, is obtained as a grey iridescent spongy mass by heating the nitrate.
It is also formed as a crystalline mass when sodium rhodochloride is heated in oxygen.
It is perfectly soluble in acids
Rhodium dioxide,
RhO2, is obtained by repeated fusions of the metal with
KOH and KNO3. It is attacked neither by alkalies nor by acids and is reduced by hydrogen
only at a high temperature.
Hydrogen sulphide precipitates from hot solution and incompletely a brown rhodium sulphide, Rh2S4.
Potassium hydroxide precipitates at first a yellow hydroxide, Rh(OHU -
f-H2O soluble in an excess of the reagent. If boiled, a gelatinous, dark-brown hydroxide, Rh(OH)3,
separates. A solution of NasRhCU does not show this reaction immediately, but the precipitate appears
in the course of time. An addition of alcohol causes a black precipitate immediately.
Ammonium hydroxide produces a yellow precipitate which is insoluble in
HCl.
Potassium nitrite precipitates from hot solutions a bright yellow precipitate
of double nitrite of potassium and rhodium.
Zinc, iron and formic acid precipitate rhodium as a black metal.
Hydrogen reduces rhodium salts.
To detect small amounts of rhodium in the presence of other metals,
evaporate the solution and displace with a fresh solution of sodium hypo-
chlorite; the yellow precipitate formed is soluble after an addition of acetic
acid. After a long agitation the solution changes to an orange-yellow color
and after a short time the color passes and finally a grey precipitate settles and the solution turns sky-blue.

ESTIMATION
Rhodium is estimated mainly in ores, thermo couples and salts.
Preparation and Solution of the Sample
When rhodium is estimated in thermo couples or other alloys of platinum
and rhodium the wire or sample is rolled to a thin ribbon and dissolved in
aqua regia. Both metals will go into solution, forming the chlorides of rhodium and platinum.
The aqua regia will have to be replaced from time to time, as the alloy dissolves slowly.

The rhodium from salts is precipitated with zinc and the black metallic
rhodium cleaned with dilute aqua regia, filtered, washed, ignited and reduced with hydrogen.
Some alloys and ores are alloyed with silver and the silver and platinum
are dissolved in HNO3. The residue is cleaned with aqua regia, dried, and
weighed as metallic rhodium. If the residue is ignited reduce with hydrogen.
The material or residue containing rhodium is fused with KHSO4 for some
time at a low red heat and the mass leached with hot water acidified with HCl.
The rose-red solution contains the rhodium.


Steve
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blueduck

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Post September 19th, 2007, 11:37 am

Re: Rhodium Tests.

seco wrote:I came across a pan load of this silverish-lightbrown reflective material in my gold pan. heavier than the black sand. Im not to sure what it is but I think it might be Rhodium. Would anyone know what i could use to test it? I have found platinum and gold in the same area.


you could have several metals other than Rh there, I pan on a creek here in Central Idaho and come up with a similat metalic lookin mineral every now and again but not in large enough quantity to do have done a fire assay, was suggested to me that it might be Monazite [scroll down to the characteristics, though SG may not be heavy enough to meet your specs you outlined] though I still dont know for sure [ i have a couple five gallon buckets of concentrates from that creek in the shop waiting for me to pan them down and I may have some of the same material] the other metals to wonder about is mercury pregnant with gold, and then some lead alloys

how much do you have of it? is it covered with a sulfide? Do you have sulfides on your ore bodies in that area? We have black telluride and brown as well and we even have some other rare metals in a couple streams around Central Idaho as well.... might want to find a shaker table to separate everything out to SG [specific gravity] and test from there Action mining M4 table is a neat little bench table I would love to get one day when i decide to get into testing things more and can justify something like that to my wife.....

William
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Irons

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Post September 19th, 2007, 12:31 pm

Specific Gravity

Rhodium is closer to Silver and Palladium in density, so it would probably wash off with the float. It rarely can be found in a free state. When it does, its so small you can barely see it under a microscope.
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Irons

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Post September 25th, 2007, 8:48 am

Rhodium test

I have noticed that when finely divided Rhodium is boiled in Sulphuric Acid, the solution may turn a faint but bright pink on heating (Rhodium Sulphate). The solution will turn clear as the solution cools and is left standing due to the precipitation of the Rhodium out of solution.

It is a very distinctive color.
The stingy man pays the most.

I cut it 3 times and it's still too short.
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Post September 25th, 2007, 10:32 am

when you say "boiled" can you be a little more specific as to temperatire of the sulfuric acid.... is that a rolling boil or just high heat..... I myself am probably not gonna attempt boiling sulfuric at this time for my laboratory is just not equipped for enough safety redundancy..... and though I am not emergency room prone, I may wait for awhile before attempting that high of a temp.

William
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Irons

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Post September 25th, 2007, 3:21 pm

Something you can do at home, if you can afford it.

30% H2SO4 heated to a simmer. Sulphuric Acid won't evaporate to any degree at that temperature. I would still take the appropriate safety precautions.

Generally, I put the test container in a borosilicate (Pyrex or equivalent) dish with enough water to heat the sample. You don't want to add too much and have your sample become unstable. I never apply a direct flame to any sample that contain PGM's. I've seen unpredictable violent reactions when samples were superheated.

Remember, PGM's are very effective catalysts and react in unpredictable ways with materials in uncontrolled situations.

This test is faint, so you have to leach out other Elements that have colored ions that would interfere with seeing the Rhodium.

Unles your concentration of Rhodium is very high, say 10-20%, it would be too faint to see with the naked eye. If you're looking at ore samples, the concentrations would probably be in the Parts per Billion range and undetectable without very sophisticated apparatus.

This won't work as a field test because the Rhodium would probably be a component of an alloy of the PGM's.

Any Iridium would probably interfere, as it is slightly soluble in H2SO4 and makes highly colored salts.

It was just an observation with a quantity of metal.

Before you fool around with Platinum Group Metals, you should study the subject.

Mistakes can be very expensive. A Troy ounce of Rhodium Spot price was $6, 030. today.

My advice is to pay the $350. or so to a reputable lab and let them do it.
The stingy man pays the most.

I cut it 3 times and it's still too short.
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Irons

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Post October 4th, 2007, 10:52 am

A handy chart

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goldsilverpro

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Post October 4th, 2007, 11:57 am

Great chart but hard to read. Not much attack by anything for Rhodium. I notice that Rhenium (Re) is listed as a Pt Gp metal. Some list it and some don't. Since Platinum Metals Review is the definitive Pt Gp publication, I guess Re should be included.

I just noticed that the chart can be magnified.
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Post October 4th, 2007, 1:47 pm

I saved the image and my viewer blew it up even better than my browser did.....

So if nothing is appreciable to corrode Rh how can one test for it?

I was watching the history channel the other day and wathed the folks in Kalifornia use Sulfuric on the alumina in cats to eat it all away before goong after the plat group..... their vat after it had been disolved and AR added was a really pretty yellow even on the tube..... they said a 400 pound barrel of cat alumina valued out at about $24,000.00 give or take when it was recorded Pt was at $1200.... so it give me some idea of what was in a cat to a degree, what they did not get into was the total process.... the show was on acids on modern marvels

http://store.aetv.com/html/product/inde ... ?id=106420

a person can buy it for $25, the segment did not last more than a few minutes.... but the whole show was worth watching as they had a chemist on there showing disintegration of a hotdog and a chicken bone in muriatic which he showed at about 9 hours as being gone...... so a fella dont want to fall into a vat of it eh?..... showed elector polishing stainless steel using acid a too and talked about that company cleaning the acid and reusing it by adding another chemical.... the program is worth catching again and might even be worth purchasing for safety lessons for some folks.

William
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Post October 4th, 2007, 7:52 pm

http://www.mininova.org/tor/919340

The residue left over from leaching the original mineral concentrate contains rhodium, iridium, ruthenium, and osmium. This is treated with molten sodium bisulfate to convert the rhodium to rhodium sulfate. The rhodium is then solubilized by water leaching, separated from the insolubles, and precipitated from solution by reduction with zinc powder. The crude rhodium metal product is converted to a soluble salt by treatment with chlorine and sodium chloride at high temperature, dissolved in water, precipitated with sodium nitrite, filtered, redissolved, and reprecipitated with ammonium chloride. This final precipitate is reduced to a pure metal powder.


This is quoted from here:

http://www.goldandsilvermines.com/platinum.htm

It sounds more like a refining method than a testing method. However, the first part is the same for the testing. You have to dissolve the sample in molten sodium bisulfate. I think the melting point is about 600F for the anhydrous variety. It's cheap as an industrial quality chemical. I would use a Coors porcelain crucible and a hot, hot plate. Rhodium, in nearly any form, will dissolve. What you do with the resulting rhodium sulfate is another story.
Last edited by goldsilverpro on October 4th, 2007, 10:23 pm, edited 2 times in total.
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lazersteve

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Post October 4th, 2007, 9:59 pm

Thodium metal from Rhodium Sulphate

Here's the method posed by web elements:

Preliminary treatment of the ore or base metal byproduct is required to remove silver, gold, palladium, and platinum. The resulting residue is melted with sodium bisulphate (NaHSO4) and the resulting mixture extracted water to give a solution containing rhodium sulphate, Rh2(SO4)3.
The rhodium is precipitated out as the hydroxide by addition of sodium hydroxide, NaOH, and redissolved in hydrochloric acid, HCl, to give H3RhCl6. This is treated with NaNO2 and NH4Cl to form a precipitate of the rhodium complex (NH4)3[Rh(NO2)6]. Dissolution of the precipitate in HCl gives a solution of pure (NH4)3RhCl6. Evaporation to dryness and burning under hydrogen gas gives pure rhodium.

Steve
Last edited by lazersteve on October 7th, 2007, 12:16 pm, edited 1 time in total.
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Post October 4th, 2007, 10:04 pm

I was jumping thru P2P sites earlier looking for that. Thanks chris. I'm going to put this on my aflac page. lol
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Post October 4th, 2007, 10:57 pm

That video is excellent, blueduck. Great visual evidence of the dangers of the acids we use. It's a must for everyone on the forum.
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Irons

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Post October 5th, 2007, 10:02 am

More Rhodium data

This is a useful site. This page provides data on emission lines.

Emission spectroscopy is an old technique and is not as sensitive as atomic absorption but it has the advantage of being able to use solid samples.

The sample is placed in a Graphite cup and a carbon rod is used as the other electrode to form an arc. The light emitted by the arc will have spectral lines that are specific to the elements present in the sample. A diffraction grating is used to break up the light into the component wavelengths and the respective emission lines show up as bright lines in the spectrum.

Try and build your own using an old CD as difraction grating. An old toaster makes a good ballast for the arc.

http://www.qivx.com/ispt/elements/ptw_045.php

It's one of my to do projects..
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Post October 5th, 2007, 8:27 pm

blueduck,

I watched the video and I think it said that the catalyst treated in sulfuric was an oil refining catalyst. The value numbers would most probably be different than autocats. Also the ceramic matrix could be different and the hydrocarbon residues on the autocat material could cause problems. The hydrocarbons could be burned off but, I read on another forum that calcining alters the ceramic composition and makes it much more impervious to the action of acids. Instead of burning, the HC could probably be removed with a solvent or, maybe, warm NaOH. All in all, though, it would be worth a trial to see if the sulfuric will dissolve the autocat ceramic, as is. The metals would then settle out. It may take a lot of acid, but the Pt Gp value is so high that it would probably be worth it. Also, the recovery would be near 100%. Large volumes of waste acid, saturated with the ceramic, would have be a big consideration.
Last edited by goldsilverpro on October 6th, 2007, 11:38 am, edited 1 time in total.
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blueduck

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Post October 5th, 2007, 11:59 pm

WEl then I guess the next step would be to tear one out and break some up and put some acid to it.....

now my question would be would the jug for replenishing a battery a fella gets down to the parts house be strong enough as is or does it need be refined/ distilled for use??? I know somewhere on the forum i read how to do so, and probably saved to disk the way to get it done and maybe it was even one of catfish's recipes that he emailed me but I know it is a source for Sulfuric, just cant remember the strength....

I am spread so thin sometimes I just cannot remember the really simple things.....

William
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aflacglobal

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Post October 6th, 2007, 12:44 am

The battery acid is about 30-35 % if i remember right. You can boil it to remove the water and concentrate the acid. Water boils at a lower temperature that the sulfuric acid, so the water will boil off first if you don't raise the temp to high. You will wind up some where in the 90% range. :arrow: :arrow: :arrow:


How to produce concentrated sulfuric acid from battery acid.

Use regular battery acid acquired from your local NAPA store. This can be purchased in one (1) quart, 1 ½ gallons, or 5 gallons quantities. This diluted acid is inexpensive.

Assumptions:

Regular battery acid is 65% water (H2O) and 35% sulfuric acid (H2SO4). This computes to 1.25 grams specific gravity per cubic cm or 1 ml. (Often referred to as 1250 specific gravity.) This is only 1.25 x 1000ml, another way of saying it.

Distilled water is 1.0 grams specific gravity per cubic cm or 1 ml.

98.3% pure sulfuric acid weighs 1.84 grams specific gravity per 1ml.

Heat required = mass x specific heat x temperature change. 1 gram of water (H2O) takes 1 calorie to change the temperature 1 degree C.

Water (H2O) boils at 212 F or 100 C.

Sulfuric acid (H2SO4) boils at 640.4 F or 338 C.

To make concentrated sulfuric acid:

Take 100 ml of battery acid and place in a heat resistant container, Pyrex or equivalent and heat on a hot plate or equivalent heat source. Preferably out doors.

Weigh 1 ml of distilled H2O in a 10ml test tube or equivalent container on a small electronic scale in grams with at least + or – 1/10th gram accuracy. This should weigh 1.0 grams. Remember to zero your meter with empty test tube on it in-order to get an accurate specific gravity weight.

Weigh 1 ml of the battery acid H2SO4 using the same procedure and you should come up with 1.20 to 1.25 SG per 1 ml. This can vary somewhat due to the charged state of the electrolyte (battery acid) no problem, this is just a relative reading.

Place hot plate in a metal container in case you have breakage or mishap. I use a metal foot tub. This also blocks the wind from the hot plate and allows it to be more efficient in heating.

Place a good grade glass thermometer in the solution and monitor.

Place on high heat and watch temperature until the solution reaches ~230 F or 110 C.

The solutions will be at a low boil and you will be able to see the boiling action and also observe the steam rising off it.

Maintain the temperature at 230 F until all boiling action stops. The steam will stop rising too. Note: the amount of time for the solution to boil off all the water will be determined by the mass of your solutions. 100ml takes about 40 to 45 minutes. This may vary due to several factors, such as ambient temperature and quantity or volume of your solution.

Let the solution cool to room temperature and take 1 ml of it and weigh it like you did the battery acid. Take the remaining solution and measure the volume that is left. It should be ~ 35 ml this time you should have a specific gravity of ~1.80 per ml. if you have boiled all the water off the solution.

The remaining acid should be 90% plus if you measure 1.80 or above. Remember that pure H2SO4 (98.3% concentration) weighs 1.84 grams per ml. Just do the math and 1.84 -1.0 =.84 /.855 (theoretical 100% Concentration) = 98.3% Realistic concentration. Divide 1.855 into your last specific gravity weight and this product will be the percentage of concentration of your finished product. Example 1.80 -1.0 =.80/.855 = 93.6%. This should meet any requirements you may encounter in the gold recovery/refining business.

This sulfuric acid is very pure and has no additives or inhibitors. It is great for the electrolytic cell and many other uses such as making nitric acid.

Be careful. Hot acid burns.

If you have any questions send me an email or post.


Catfish
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4. Chemistry Handbooks Here (FREE) >> http://tinyurl.com/n27pqu
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blueduck

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Post October 6th, 2007, 1:05 am

Thanks

As soon as i started reading the procedure i knew where i have it located, now i have it printed out and put inside my notebook where it should have been but i had not got to it yet.....

William
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goldsilverpro

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Post October 6th, 2007, 7:29 am

I don't know what strength you need, blueduck. It didn't say. The battery acid may be strong enough. It may even be too strong. Temperature could be a big factor. I would do some small experiments in, say, 5 or 10 gram samples. When you experiment, weigh and measure everything and keep records. It makes your life easier when you gear up.
Last edited by goldsilverpro on October 6th, 2007, 11:40 am, edited 1 time in total.
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