Sciencemadness Discussion Board

On the heating of Arsenic in H2SO4

6dthjd1 - 6-11-2023 at 11:00

For the past two hours I have 107 g of Arsenic rock in 114 ml of Rooto Sulfuric acid


So far barely any acid seems to be consumed. Although dropping the Arsenic in the H2SO4 did result in white swirls within 10 minutes and within 1 hr the solution went dark.


The hotplate used is a 120 volt 8 amp hotplate stirrer combo. The heat is set to high with no covering used to shield the beaker (I would usually use aluminum foil). There is evolution of SO2 and some bubbling does exist. As the acid has receded a white film appears on the beaker. This hotplate barely is able to boil water even with a shield IIRC.

I estimate I will have a low yield of arsenic trioxide. Perhaps I shall dissolve the remnants in 70% nitric acid and heat at around 100 C to get the trioxide.

It very much does seem that heating sulfuric acid and arsenic may result in an appreciable quantity of some white arsenic compound by only with great patience.

Texium - 6-11-2023 at 11:18

Going into arsenic chemistry on a 100 gram scale with seemingly no reference or plan is a really bad idea…

clearly_not_atara - 6-11-2023 at 11:34

Use a real oxidizer you suicidal maniac

6dthjd1 - 6-11-2023 at 14:24

Quote: Originally posted by clearly_not_atara  
Use a real oxidizer you suicidal maniac



The reaction with nitric is a bit more vigorous and would still require heating to form the trioxide. The late and post 19th century literature prefers the use of nitric for oxidizing elemental arsenic though some of the 19th century literature also mentions this as well. Some of this literature exists in the sciencemadness library.

Care must be taken not to heat too vigorously as sublimation of the trioxide is a real possibility. Also it goes without saying doing this inside in unventilated places is a no no.

I should note formation of the trioxide by even more dangerous processes such as heating auripigmentum or burning arsenic in air were done by alchemists and early chemists with little ventilation. In some of this literature they were mostly concerned with ingestion of arsenic. They unfortunately did not do anything outside on windy days and maintaining fires outside on windy days would be a chore using old technology.


My review of the literature over the years suggests that many of the group 15 elements react slowly or very slowly with concentrated sulphuric acid. Like antimony.

Admagistr - 6-11-2023 at 15:14

I wonder how old these ancient chemists and alchemists lived?How old did they die.Take care of yourself,make sure you are here for a long time,so you can do many more interesting experiments!You can get partial immunity to arsenic.But they say it can cause cancer...Are you planning experiments with other risky elements?

andyloris - 7-11-2023 at 03:40

How are you going to dispose of the waste ?

Rainwater - 7-11-2023 at 06:10

Chemistry without a plan, is like a racecar without a track. Hes got to have one, just not saying what it is.
I had no trouble, accidentally bringing almost 20g of arsenic ore into solution with aqua regia once.
Nice colors. Scary situation.
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...

[Edited on 7-11-2023 by Rainwater]

RU_KLO - 7-11-2023 at 09:25

Quote: Originally posted by 6dthjd1  


My review of the literature over the years suggests that many of the group 15 elements react slowly or very slowly with concentrated sulphuric acid. Like antimony.



This is not my experience with antimony. OK, I worked with 10 mgr. (hand filed from pure antimony metal in 2 cm3 of 98% H2SO4 in a test tube. it disolved compleatly on heating in 30 minutes)

Maybe you could speed your reaction by grinding/pulverizing the rock.

Also I read a lot of 19th century books, it seems that "safety and responsible practices" where not an issue. For example they use mercury and lead as they where as safe as sodium bicarbonate.....

woelen - 8-11-2023 at 00:22

@6dthjd1: If I read your posts, then it really raises my concerns. If you had white 'frost' on your beaker and near your beaker, then some arsenic trioxode may have escaped. If the solution bubbled with SO2, then the bubbles of SO2 also may have taken with them small droplets, containing dissolved arsenious compounds. Did you smell the SO2 (it has quite a pungent smell, somewhat reminiscent of burning matches)? If so, then you also may have inhaled some arsenic compounds with it!

Your experiments sound like sollicitating for health issues. Keep in mind that arsenic is both an acute poison and a long-term poison.

I never would do this kind of experiments on a large 100 g scale. I do not say that you should not do this kind of experiments (I myself also did some small-scale experiments with arsenic compounds), but keep things small (100's of milligrams) and keep things confined to liquids. No bubbling of gases from these toxic liquids should occur, unless you are really sure that you do not inhale anything from the produced gases. Waste also must be processed correctly. With your scale of experimenting you also produce quite some really nasty toxic waste, which must be safely disposed of.

[Edited on 8-11-23 by woelen]

6dthjd1 - 8-11-2023 at 09:44

Quote: Originally posted by woelen  
@6dthjd1: If I read your posts, then it really raises my concerns. If you had white 'frost' on your beaker and near your beaker, then some arsenic trioxode may have escaped. If the solution bubbled with SO2, then the bubbles of SO2 also may have taken with them small droplets, containing dissolved arsenious compounds. Did you smell the SO2 (it has quite a pungent smell, somewhat reminiscent of burning matches)? If so, then you also may have inhaled some arsenic compounds with it!

Your experiments sound like sollicitating for health issues. Keep in mind that arsenic is both an acute poison and a long-term poison.

I never would do this kind of experiments on a large 100 g scale. I do not say that you should not do this kind of experiments (I myself also did some small-scale experiments with arsenic compounds), but keep things small (100's of milligrams) and keep things confined to liquids. No bubbling of gases from these toxic liquids should occur, unless you are really sure that you do not inhale anything from the produced gases. Waste also must be processed correctly. With your scale of experimenting you also produce quite some really nasty toxic waste, which must be safely disposed of.

[Edited on 8-11-23 by woelen]


I did catch a few wiffs of sulfur dioxide. I worked hard to stay more than 6 feet away from the setup as much as possible.

I did this outside. It was one of this windy months in the Great Lakes. wind speeds exceed appx 20km/h at times.


I'm too scared to do this inside

6dthjd1 - 8-11-2023 at 09:46

Quote: Originally posted by Admagistr  
I wonder how old these ancient chemists and alchemists lived?How old did they die.Take care of yourself,make sure you are here for a long time,so you can do many more interesting experiments!You can get partial immunity to arsenic.But they say it can cause cancer...Are you planning experiments with other risky elements?


Some of them died in their 60s like most people then who lived to see 20.

Others like Scheele died in their 30s or 40s. Scheele ate at lot of his chemicals over time. It was known that many apothecaries did die in his day. Makes sense if you are going to taste the butter of arsenic and more

6dthjd1 - 8-11-2023 at 09:48

Quote: Originally posted by RU_KLO  
Quote: Originally posted by 6dthjd1  


My review of the literature over the years suggests that many of the group 15 elements react slowly or very slowly with concentrated sulphuric acid. Like antimony.



This is not my experience with antimony. OK, I worked with 10 mgr. (hand filed from pure antimony metal in 2 cm3 of 98% H2SO4 in a test tube. it disolved compleatly on heating in 30 minutes)

Maybe you could speed your reaction by grinding/pulverizing the rock.

Also I read a lot of 19th century books, it seems that "safety and responsible practices" where not an issue. For example they use mercury and lead as they where as safe as sodium bicarbonate.....


When Robert Bunsen first worked with Cacodyl derivatives he would pass out from the acute toxicitiy imminently


It was so bad he had to breathe through a tube which projected from the window.

6dthjd1 - 8-11-2023 at 09:51

Quote: Originally posted by Rainwater  
Chemistry without a plan, is like a racecar without a track. Hes got to have one, just not saying what it is.
I had no trouble, accidentally bringing almost 20g of arsenic ore into solution with aqua regia once.
Nice colors. Scary situation.
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...

[Edited on 7-11-2023 by Rainwater]


Eventually i may use the trioxide to heat with anhydrous copper (ii) sulfate and sodium chloride to generate Arsenic trichloride in a manner similar to how Glauber did it.

I will likely acquire different glassware and use a charcoal fire to do so. I know Newton's method of generating sulfuric acid using virtriol as repeated by modern chemists resulted in the deformation of glass

Rainwater - 8-11-2023 at 12:41

Crazy hard to work with in a professional environment.
In the states, it's labled as "extremely hazardous substance" and requires permits to produce/store/use in any amounts.

The only legitimate purpose for this compound I know of is the purification of arsenic for use in semiconductors.

woelen - 9-11-2023 at 02:50

Making AsCl3 in a home-setting, while I read this in the "beginnings" subforum??? :o Don't do this!

AsCl3 is volatile and very reactive. Even professional labs shy away from using this. Keeping it contained and avoiding exposure is nearly impossible due to its properties. The only safe way of storing it is in a completely sealed glass ampoule, and once you break it to do something with it, you put yourself at great risk. Making this stuff in or around your home is even more dangerous.

You inhaled some of the SO2, possibly contaminated with arsenic compounds. This already demonstrates how difficult it is to get not exposed. With the SO2 mixed in, you at least know that you might have been exposed to arsenic compounds, but in many experiments you will not have such a warning-compound besides the arsenic.

My advice: quit this endeavor, there are better ways to fill your time.


[Edited on 9-11-23 by woelen]

B(a)P - 9-11-2023 at 11:56

If you are going to embark on the synthesis of arsenic trichloride, you should know that it adsorbs through most types of PPE, it can not be detected by smell until you are exposed at a concentration that is doing serious damage to your body. A half or full faced respirator will not provide you adequate protection.
I once worked on the clean up of an old chemical warfare facility and arsenic trichloride was one of the contaminants. We were working outside in a well ventilated area. Despite this we still needed to be in fully enclosed suits with supplied air. This is not something that is possible to do safely in the home chemistry environment.

Texium - 9-11-2023 at 14:20

Do not even think of posting about making arsenic trichloride. I can assure you it will immediately be sent to Detritus and you may be banned.

clearly_not_atara - 9-11-2023 at 20:48

The two safest ways I can think of to do this are:

- bubble ozone through the sulfuric acid with a cooling bath

- anodic oxidation in KOH solution to the arsenite

Thermal oxidation ain't it.

But even then, it's sort of like asking the safest way to go over Niagra Falls in a barrel. Think carefully about whether you want to risk a potentially permanent injury to mess with the king of poisons.

Bedlasky - 10-11-2023 at 03:12

Quote: Originally posted by clearly_not_atara  
The two safest ways I can think of to do this are:

- bubble ozone through the sulfuric acid with a cooling bath

- anodic oxidation in KOH solution to the arsenite


I think that nitric acid is probably the safest and easiest way of doing it. However after reading 6dthjd1's posts, I strongly recommended him to abandon this stupid idea. Working with arsenic require experience and very good safety precautions.

Rainwater - 10-11-2023 at 11:42

Lookup David Hahn, Robert Oppenheimer, Marie Curie,Harold Maxwell, Louis Slotin, Karen Wetterhahn.
Their research should help you with your experment.

clearly_not_atara - 10-11-2023 at 12:49

Quote: Originally posted by Bedlasky  
Quote: Originally posted by clearly_not_atara  
The two safest ways I can think of to do this are:

- bubble ozone through the sulfuric acid with a cooling bath

- anodic oxidation in KOH solution to the arsenite


I think that nitric acid is probably the safest and easiest way of doing it. However after reading 6dthjd1's posts, I strongly recommended him to abandon this stupid idea. Working with arsenic require experience and very good safety precautions.

I would expect ozone to work at lower temperatures than nitric acid and for oxidation in sodium hydroxide to produce the least volatilization of any method. Why would you prefer nitric acid?

Bedlasky - 10-11-2023 at 14:28

Oxidation by nitric acid is relatively quick. You must bubble ozone through solution for prolonged time, because its inefficient generation from the air. Electrolysis also needs to be run for long time. So even though volatilization of arsenic is less significant than with nitric acid method, you create arsenic containing aerosols for longer.

j_sum1 - 10-11-2023 at 16:10

This just seems like a disaster on so many fronts.
The scale is ridiculous.
As is seriously nasty and unforgiving.
The required level of knowledge and skill just isn't there.
Numerous chemists better than me have itemised specific risks, which are just frightening.
And, thus far, there has not been any thought given to waste and disposal.

Time to just drop this fool's errand.

6dthjd1 - 18-11-2023 at 21:29

Quote: Originally posted by clearly_not_atara  
Quote: Originally posted by Bedlasky  
Quote: Originally posted by clearly_not_atara  
The two safest ways I can think of to do this are:

- bubble ozone through the sulfuric acid with a cooling bath

- anodic oxidation in KOH solution to the arsenite


I think that nitric acid is probably the safest and easiest way of doing it. However after reading 6dthjd1's posts, I strongly recommended him to abandon this stupid idea. Working with arsenic require experience and very good safety precautions.

I would expect ozone to work at lower temperatures than nitric acid and for oxidation in sodium hydroxide to produce the least volatilization of any method. Why would you prefer nitric acid?


I prefer nitric for greater certainty. The nitric acid comes up more consistently across 19th and 20th century literature at least from what I have seen since 2011. I also happen to have around 600 ml of it at the moment as reagent grade ACS purity and it's more convenient for me to make more nitric of an inferior purity if need be.



The nitric acid method isn't incompatible with the final waste product which will be a calcium arsenite which is insoluble in water. (Sodium hydroxide dissolves residues to form sodium arsenite/nitrate in a container dedicated to arsenic which will then be charged with calcium chloride to form calcium arsenite).