Preparing DMG

[Geo]

I have tried and failed to fully dissolve DMG. I tried ethanol and isopropyl alcohol. Yesterday I tried sodium hydroxide. I did get a partial dissolution in the sodium hydroxide but there was still a lot of solid white powder left where it did not fully dissolve. I kept adding hydroxide until the solution formed a skin of film on top. I have very little experience and don't really know quantities such as how much DMG will dissolve in a certain volume of water. How much hydroxide is needed to dissolve X amount of DMG. How much water is needed. I was told that 100 grams of DMG will precipitate 30 grams of Pd in salt form. I believe I dropped more than that with just a few grams of DMG but wont know until it's converted. Can someone give me some insight on what I'm doing and how it should be done?

 

[FrugalRefiner]

DMG is sparingly soluble in water. I found the following information while researching.

0.06 g. / 100 ml. (20°C)
0.36 g. / 100 ml. (80°C)
0.59 g. / 100 ml. (100°C)

source dimethylglyoxime

I've only used it for testing, so never tried alcohol or NaOH to increase solubility.

Dave

 

[snail]

Found an old post from 2013 about making test solution:


- When you use NaOH to prepare your DMG you only use 4 grams of NaOh per 100 ml of water which will dissolve 5.8 grams of DMG --- so thats not an enormous amount of NaOH --- 43 ml of DMG prepared this way will precip 1 gram PD

 

[kurtak]

Found an old post from 2013 about making test solution:


- When you use NaOH to prepare your DMG you only use 4 grams of NaOh per 100 ml of water which will dissolve 5.8 grams of DMG --- so thats not an enormous amount of NaOH --- 43 ml of DMG prepared this way will precip 1 gram PD

This is correct

100 ml distilled water - best to heat the water - it just needs to be to the hot side of warm - not boiling
4 gr NaOH
5.81 gr DMG

Get your water to the hot side of warm - add your NaOH - then add your DMG - the DMG should dissolve "almost" instantly & completely

I tried ethanol and isopropyl alcohol.

WARNING - be VARY careful using DMG prepared with "any" kind of alcohol - NEVER use DMG on a nitric solution that has silver & palladium dissolved in the same solution

Adding alcohol(s) to a silver nitrate solution is how you make (precipitate) silver fulminate - silver fulminate is a VERY pressure sensitive primary explosive - it is so pressure sensitive that it can/will detonate under it's own weight & while wet - in other words explode when precipitating & piling up in the bottom of the beaker

A few things from Wiki about silver fulminate ----------

Silver fulminate is a primary explosive, but has limited use as such due to its extreme sensitivity to impact, heat, pressure, and electricity. The compound becomes progressively sensitive as it is aggregated, even in small amounts; the touch of a falling feather, the impact of a single water droplet, or a small static discharge are all capable of explosively detonating an unconfined pile of silver fulminate no larger than a dime and no heavier than a few milligrams. Aggregating larger quantities is impossible, due to the compound's tendency to self-detonate under its own weight.

Silver fulminate can be prepared unintentionally, when an acidic solution of silver nitrate comes in contact with alcohol

Therefore - NEVER use DMG prepared with any kind of alcohol if you intend to precipitate Pd from a nitrate solution that also has silver dissolved in it

Silver fulminate can also be made with a combination of silver carbonate plus ammonia

Use the (above) hot water + NaOH + DMG method for dissolving your DMG - it's the ONLY way I will prepare my DMG - it only takes about 10 minutes to prepare it - it works VERY well - & I have used it to precipitate relatively large amounts of Pd from Ag/Pd nitrate solutions

Kurt

 

[kurtak]

Here is a couple pics of Pd precipitated from a couple of silver nitrate solutions with DMG (as prepared above) as well the Pd after calcination of the Pd/DMG salt

Note that the Pd/DMG (on the left) is not the bright canary yellow - that is because the solution had nickel as well as silver & Pd in it so "some" nickel also came down

Also note that in the pic of the calcinated Pd/DMG salt the calcination is not quite complete - it needed to be crushed to a finer powder & put back on the heat to complete calcination

The black in the pic of the salts is Pd after completed calcination

Kurt

 

[goldandsilver123]

It will dissolve much better if you add NaOH to the water first, then add the DMG

 

[kurtak]

It will dissolve much better if you add NaOH to the water first, then add the DMG

Isn't that what I said ???

Get your water to the hot side of warm - add your NaOH - then add your DMG

per the bold print

Kurt

 

[Stibnut]

This is correct

100 ml distilled water - best to heat the water - it just needs to be to the hot side of warm - not boiling
4 gr NaOH
5.81 gr DMG

Get your water to the hot side of warm - add your NaOH - then add your DMG - the DMG should dissolve "almost" instantly & completely


WARNING - be VARY careful using DMG prepared with "any" kind of alcohol - NEVER use DMG on a nitric solution that has silver & palladium dissolved in the same solution

Adding alcohol(s) to a silver nitrate solution is how you make (precipitate) silver fulminate - silver fulminate is a VERY pressure sensitive primary explosive - it is so pressure sensitive that it can/will detonate under it's own weight & while wet - in other words explode when precipitating & piling up in the bottom of the beaker

A few things from Wiki about silver fulminate ----------

Silver fulminate is a primary explosive, but has limited use as such due to its extreme sensitivity to impact, heat, pressure, and electricity. The compound becomes progressively sensitive as it is aggregated, even in small amounts; the touch of a falling feather, the impact of a single water droplet, or a small static discharge are all capable of explosively detonating an unconfined pile of silver fulminate no larger than a dime and no heavier than a few milligrams. Aggregating larger quantities is impossible, due to the compound's tendency to self-detonate under its own weight.

Silver fulminate can be prepared unintentionally, when an acidic solution of silver nitrate comes in contact with alcohol

Therefore - NEVER use DMG prepared with any kind of alcohol if you intend to precipitate Pd from a nitrate solution that also has silver dissolved in it

Silver fulminate can also be made with a combination of silver carbonate plus ammonia

Use the (above) hot water + NaOH + DMG method for dissolving your DMG - it's the ONLY way I will prepare my DMG - it only takes about 10 minutes to prepare it - it works VERY well - & I have used it to precipitate relatively large amounts of Pd from Ag/Pd nitrate solutions

Kurt

Silver fulminate will form when ethanol is used, but do any explosive compounds form when other alcohols like methanol or isopropyl alcohol contact acidic silver nitrate solutions?

edit to add: Maybe nitrate esters (e.g. methyl nitrate, isopropyl nitrate) are a concern? I would imagine that you'd have to do something to remove water (e.g. distill or add sulfuric acid) to actually form them in quantity though.

 

[goldandsilver123]

Isn't that what I said ???



per the bold print

Kurt

I clicked to anwser before your reply. but only after a few hours I got time to write it, so I never saw it before posting.

 

[Geo]

I have a source of cheap 99.99% acetate. DMG will dissolve in acetate. Is there any such danger using acetate?

 

[kurtak]

Silver fulminate will form when ethanol is used,

Correct - ethanal is the alcohol used when intentionally making silver nitrate

but do any explosive compounds form when other alcohols like methanol or isopropyl alcohol contact acidic silver nitrate solutions?

however - according to Wiki it says --- "Silver fulminate can be prepared unintentionally, when an acidic solution of silver nitrate comes in contact with alcohol

Alcohol is a general term that includes ethanol, methanol & isopropyl (as well as other alcohols)

What alcohols have in common is C (carbon) H (hydrogen) bonded to at least 1 -OH (hydroxyl) which I believe is the mechanism that precipitates the silver fulminate - & why Wiki warns that silver fulminate can be unintentionally made with silver nitrate plus alcohol

I would imagine that you'd have to do something to remove water to actually form them in quantity though.

Another interesting note from Wiki says that silver fulminate is slightly soluble in cold water but recrystallizes in hot water - so water would play only "somewhat" of a roll

IMO - there is NO reason to prepare DMG with alcohol when it can be done with water + NaOH + DMG --- that for sure will not precipitate silver fulminate

Kurt

 

[kurtak]

I have a source of cheap 99.99% acetate. DMG will dissolve in acetate. Is there any such danger using acetate?

I don't know - however - according to Wiki --- It can also be recrystallized from a 20% solution of ammonium acetate

IMO - why play around with chemistry when water + NaOH dissolves DMG

Kurt

 

[kurtak]

I clicked to anwser before your reply. but only after a few hours I got time to write it, so I never saw it before posting.

Ok - I get that as I have done that many times myself

Thank you

Kurt

 

[Hombressino]

Hi Kurt,
thanks for valuable information. I found reference to ethanol in "DMG testing solution" thread here:
https://goldrefiningforum.com/threads/dmg-testing-solution.2994/So it may be worth to link your safety information to it. I'm not sure how to do it correctly (I won't to mess things up here at GRF).

 

[Geo]

Thank you Kurt. I followed your directions carefully. I think my DMG is faulty but it's all I have. It does dissolve, for the most part, but just very, very slowly with lots of stirring. I worked on it for hours last night trying to figure out what I was doing wrong. I can only blame it on the DMG. I found that by stirring with a glass rod and letting the rod rub the side of the beaker kind of forces the DMG to come into greater contact with the solution. The DMG is very hydrophobic and actually crawls up the side of the beaker while stirring. A good portion stays clinging to the beaker as a dry powder and never really gets "wet". And there always seems to be a small portion that stays a dry powder even after staying hot and stirring for as long as 10 minutes. But, I did manage to drop the Pd completely from solution. There was still white nodules of DMG that didn't break down or dissolve but I can't see it causing problems during calcining. I was ready to give up and toss it. Now I'm confident that I can use this effectively. Thanks again.

 

[4metals]

Dimethylglyoxime is soluble in methylsulfoxide which is not an alcohol, it is an organosulfur compound. You can make concentrated solutions of Dimethylglyoxime with this.

 

[orvi]

Dimethylglyoxime is soluble in methylsulfoxide which is not an alcohol, it is an organosulfur compound. You can make concentrated solutions of Dimethylglyoxime with this.

I have bad experience with DMSO used as solvent for DMG. Solubility isn´t bad, but as I mixed the DMSO solution of DMG with PGM solution, extremely fine, mud-like precipitate immediately formed, which was real pain to filter and wash. And it draged another PGMs with it, but just like 1-3% each. Maybe I messed something up, after this one experience, I didn´t used the DMSO as solvent for DMG since this experiment. I also do not like the idea of adding bunch of organic solvent to the PM solution, which could possibly mess up reactivities and solubilities of other components, since medium composition change.

I used to make Na-DMG solution from NaOH and DMG, and it kinda worked better than plain powder. In bulk, I just add DMG powder to vigorously stirred solution and let it equilibrate/adsorb the palladium for like 30 minutes. If base metals are present in solution, they help to dissolve tiny bits of DMG into the solution - as DMG create complexes with nearly every metal, but they are freely soluble. So the DMG is taken into the solution, find the Pd cations and drop like insoluble Pd(DMG)2 complex.

 

[4metals]

Back in the day of no (or crazy expensive) XRF I used the Dimethylglyoxime DMSO which I filtered before use and storage to drop Palladium out of fire assay parting acids when assaying dental scrap. The concentrate needed a few drops to drop any Palladium which was filtered onto a tared mini buchner funnel, dried in a dessicator, and weighed as Palladium Dimethylglyoxime. Simplified the analysis as the alloys were Gold Palladium and easily separated with Dimethylglyoxime. Only needing a few concentrated drops was the appeal, and a parting flask from a half gram sample only contained a fraction of a gram of Palladium.