Sciencemadness Discussion Board - Chemical combinations to avoid

Chemical combinations to avoid

Sulaiman - 18-10-2015 at 06:35

I have been reading through the phosgene threads ... scary,
and even though my best years are behind me I have no intention of making any (at my current skill level

If I follow well prescribed experiments the dangers are usually highlighted,
but when I start messing around with 'random' chemical mixtures I do not have the required knowledge/experience to determine if any 'nasty' side reactions will occur,
so I'm wondering if there is a list of generally hazardous mixtures?
I would not want a terrorist cookbook to be made, just warnings of potential hazards.

e.g. I have learned that conc. HNO3, NH3, or H2O2 easily form explosive compounds
and chlorine containing compounds can release Cl2 gas (due to the small scales that I use and the strong smell, I'm not too worried about Cl2)
so, I presently have no fluorine containing compounds. I also have no cyanides at the moment for similar reasons.

So, is there a list of things NOT to mix?

If not then would it be worth making a 'sticky' to reduce the risks for the less experienced amongst us?

so far I have found stuff like this;
http://chemistry.about.com/cs/toxicchemicals/a/aa603003a.htm

hazardous chemicals;
https://en.wikipedia.org/wiki/List_of_extremely_hazardous_su...
https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_tab...
http://ccc.chem.pitt.edu/wipf/Web/HCH.pdf (this is a generally useful document)

mayko - 18-10-2015 at 06:58

Chloromethylethers, from the reaction of formaldehyde and hydrochloric acid, have always struck me as a disaster lying in wait for a home chemist.

annaandherdad - 18-10-2015 at 08:19

I did some experiments once using hydrogen to reduce metal oxides. Copper works very well, and makes a beautiful demo. I also managed to reduce iron oxides. Then I started thinking about other metal oxides, and maybe using CO as a reducing agent. Part of the motivation for this is that CO is the actual reducing agent in old fashioned ways of making iron. Of course I know the dangers of CO, and I was planning to take that into account.

What I didn't realize is that CO reacts with nickel to make nickel carbonyl, which is extremely toxic, much more so than CO itself.

ave369 - 18-10-2015 at 08:46

* Hypochlorite and acid, especially hydrochloric. Instant chlorine attack.
* Cyanoferrates and heat. Cyanoferrates and acids. Hell, cyanoferrates and everything except things they are supposed to react with.
* Fluorides and acids. Not only you can be poisoned, you might ruin your glassware.
* Concentrated nitric acid and metals in large amounts, if you don't have a fume hood. The "fox tail" is impressive, and the foaming acid can even overflow the flask.
* Fuming nitric acid and rubber gloves (butyl rubber is safe, the other types aren't).

woelen - 18-10-2015 at 09:49

Cyanoferrates (especially the yellow variation) are surprisingly stable and the risk of poisoning yourself with hydrogen cyanide is highly overrated. I have done experiments with K3Fe(CN)6 and K4Fe(CN)6 in combination with 20% HCl or 20% H2SO4. No problem at all. Only the combination of heat and strong acid at quite high concentration can release HCN, and even then the reaction is incomplete and has many side reactions. If this reaction were indeed as easy as many people tend to believe, then cyanoferrates would be much more popular for making your home-made cyanide salts.

Some unexpected and really dangerous reactions:
- Mix dry calcium hypochlorite with TCCA or Na-DCCA and add a small amount of water. A very violent reaction starts, with charring of the material and possibly explosion. A lot of toxic fumes are released as well. Both are swimming pool chlorine compouds, but the hypochlorites and chlorinated cyanuric acid derivatives are not compatible with each other.
- Solid chlorites with reductors. These mixes are very sensitive, even more so than chlorates. Chlorites are easy to obtain and are sold without questions asked, because of their use as MMS or for water purification. In solid form, sodium chlorite is quite dangerous.
- TCCA in itself is one of the more dangerous chemicals and I still am surprised that this is sold to the general public. With organics it can lead to extremely exothermic reactions, leading to fire, especially if some acid is added as well. With ammonia, the reaction of TCCA is explosive (try mixing a pea sized, NOT LARGER, piece of TCCA with 12% ammonia or 25% ammonia, you will be impressed, this is more violent than potassium with water!).

AJKOER - 19-10-2015 at 11:47

A somewhat more general statement per part of Woelen's comment is the classic mistake of mixing ammonia (or ammonium salts, or amines, or urea) and chlorine in excess (or an excess of hypochlorous acid or compounds creating it like TCCA plus water, Ca(ClO)2 plus moisture + CO2).

The resulting yellow oily liquid is a totally impractical high explosive detonating on exposure to organics, sunlight, heat, shock,...

[Edited on 19-10-2015 by AJKOER]

careysub - 19-10-2015 at 14:42

This segues into chemical storage guidelines in general. Every chemical storage guideline document is going to a have a section devoted to chemical incompatibilities:

https://www.towson.edu/adminfinance/facilities/ehs/documents...

kecskesajt - 19-10-2015 at 20:15

Chloroform with ammonia.(HCN)
Or chloroform with warm,concentrated nitrating acid.(CCl3NO2)
Ca(OCl)2 and ammonia.H4N2,NCl3,NH2Cl and NHCl2
Ca(OCl)2 and cc. H2SO4. Rapid explosion
H2SO5 and solvents. Violent explosion
ClF3 and anything.Even concrete will burn

woelen - 19-10-2015 at 22:58

Quote: Originally posted by kecskesajt

Chloroform with ammonia.(HCN)
Or chloroform with warm,concentrated nitrating acid.(CCl3NO2)
Ca(OCl)2 and ammonia.H4N2,NCl3,NH2Cl and NHCl2
Ca(OCl)2 and cc. H2SO4. Rapid explosion
H2SO5 and solvents. Violent explosion
ClF3 and anything.Even concrete will burn

The first reaction hardly occurs. It is very slow. Maybe in anhydrous conditions, but mixing some CHCl3 with 12% household ammonia certainly does not lead to formation of dangerous amounts of HCN.

H2SO5 and ClF3 are not compounds which the average (or even well equipped) home chemist has at home.

fluorescence - 20-10-2015 at 01:22

As a Cyanide Chemist I find that its not only the reaction with acids or water but also redox reactions with certain metals, especially copper. It will produce gases like Dicyan. Also some noble metal cyanides can give of toxic compounds if decomposed. So before you do any work with it you should check for side reactions with your other educts.

woelen - 20-10-2015 at 03:35

Another cyanide danger: Oxidation of thiocyanate (thiocyanate itself being only moderately toxic) by hydrogen peroxide in acidic solution. This oxidation may lead to formation of HCN. Whether dangerous amounts of HCN can escape from the liquid is uncertain. Usually, concentrations are too low to have large amounts of HCN in the surrounding air, but if this reaction occurs with large quantities, then it is something to take into account.

[Edited on 20-10-15 by woelen]

kecskesajt - 20-10-2015 at 05:42

25% ammonia and CHCl3 are mixed.Then there is going to be a runnaway reaction.

woelen - 20-10-2015 at 06:02

But in this runaway I expect no HCN to be formed.

MeshPL - 20-10-2015 at 12:12

H2SO5 is nothing else than H2SO4 and H2O2. Obviously resulting concentration is laughable... and exists in equilibrium... but when you try adding some organics, you may change your mind.

Little_Ghost_again - 21-10-2015 at 00:44

Quote: Originally posted by woelen

Cyanoferrates (especially the yellow variation) are surprisingly stable and the risk of poisoning yourself with hydrogen cyanide is highly overrated. I have done experiments with K3Fe(CN)6 and K4Fe(CN)6 in combination with 20% HCl or 20% H2SO4. No problem at all. Only the combination of heat and strong acid at quite high concentration can release HCN, and even then the reaction is incomplete and has many side reactions. If this reaction were indeed as easy as many people tend to believe, then cyanoferrates would be much more popular for making your home-made cyanide salts.

Some unexpected and really dangerous reactions:
- Mix dry calcium hypochlorite with TCCA or Na-DCCA and add a small amount of water. A very violent reaction starts, with charring of the material and possibly explosion. A lot of toxic fumes are released as well. Both are swimming pool chlorine compouds, but the hypochlorites and chlorinated cyanuric acid derivatives are not compatible with each other.
- Solid chlorites with reductors. These mixes are very sensitive, even more so than chlorates. Chlorites are easy to obtain and are sold without questions asked, because of their use as MMS or for water purification. In solid form, sodium chlorite is quite dangerous.
- TCCA in itself is one of the more dangerous chemicals and I still am surprised that this is sold to the general public. With organics it can lead to extremely exothermic reactions, leading to fire, especially if some acid is added as well. With ammonia, the reaction of TCCA is explosive (try mixing a pea sized, NOT LARGER, piece of TCCA with 12% ammonia or 25% ammonia, you will be impressed, this is more violent than potassium with water!).

Thank you Woelen,

I have been making bleach etc for the haloform reaction and have both of these chemicals which I have used.
reading this stopped me trying something out while I trying to get a high amount of free chlorine.
I had assumed mixing these two would not be a problem! I am grateful to the op and Woelen for posting this information, so many combinations would seem safe logically but not in reality.

I tried the small scale version as suggested (just to see what happens) I used half a pea size as I am a bit of coward! while impressed with the reaction I am totally unimpressed with the soiled underwear! Despite the warning that its more vigorous than potassium (only seen that on you tube) I wasnt expecting just how upset it gets with ammonia!

I would kind of like to do it again now I know what to expect, but for me its one of those ok seen it no need to try that again things!!
I think this thread or one like should be a sticky.

Eddygp - 21-10-2015 at 07:03

Worries/grief/self-consciousness + ethanol

chornedsnorkack - 21-10-2015 at 23:06

Quote: Originally posted by careysub

Every chemical storage guideline document is going to a have a section devoted to chemical incompatibilities:

https://www.towson.edu/adminfinance/facilities/ehs/documents...

Like most such lists, it inspires mostly ridicule and irritation, and some curiosity. For grounds such as what their grounds for omission and inclusion might be - very illogical.

Do you want to start going through the list?

careysub - 22-10-2015 at 10:10

Quote: Originally posted by chornedsnorkack

Quote: Originally posted by careysub

Every chemical storage guideline document is going to a have a section devoted to chemical incompatibilities:

https://www.towson.edu/adminfinance/facilities/ehs/documents...

Why don't you show us how its done?

chornedsnorkack - 22-10-2015 at 13:07

Starting...

Quote:

Acids (Strong) Bases (Strong)

Fine, worried about heat of neutralization...

Quote:

Alkali Metals Water, Carbon Dioxide, Carbon Tetrachloride, and other chlorinated Hydrocarbons

Alkali metals and water, fine - but they completely omit to mention acids, or any other oxidants.
For curiosity part, how easily do alkali metals react with carbon dioxide, as compared to oxygen?
"other chlorinated hydrocarbons"? Alkali metals with chlorinated hydrocarbons is a standard way of producing hydrocarbons. A halocarbon with too many halogens might get violent, and also not give a useful specific product, though.
And why single out chlorocarbons? Are alkali metals by omission safe with bromocarbons, iodocarbons or fluorocarbons?

With stuff as reactive as alkali metals, "incompatibilities" gets uselessly big by any meaningful standard of inclusion. Actually, you should do the opposite. List substances which either do not react with alkali metals, or do but do so in a quiet and safe manner.

zed - 22-10-2015 at 13:41

"Today is a good day to die!" Supposed to be a Souix saying.

Suliman, everytime I start a new project, I ponder long and hard about the possible dangers. I read all about the known problems, and I try to consult someone who has done something similar. I visit Org. Synthesis.....where experiments are usually accompanied by a list of cautions.

There are often many many things that can go wrong. As such, the road to Hell, is quite probably paved with dead chemists.

Sometimes there are deadly consequences, associated with common procedures.
So, I approach every project as if it might be a very dangerous project.

"Cyanoferrates (especially the yellow variation) are surprisingly stable and the risk of poisoning yourself with hydrogen cyanide is highly overrated. I have done experiments with K3Fe(CN)6 and K4Fe(CN)6 in combination with 20% HCl or 20% H2SO4. No problem at all. Only the combination of heat and strong acid at quite high concentration can release HCN, and even then the reaction is incomplete and has many side reactions. If this reaction were indeed as easy as many people tend to believe, then cyanoferrates would be much more popular for making your home-made cyanide salts"

While these complex salts aren't very toxic, they are wildly explosive when mixed with certain oxidizing agents. They can detonate without confinement. Though it usually takes a spark or whatnot to set 'em off.

https://www.youtube.com/watch?v=fPIVZo6QpBg
https://www.youtube.com/watch?v=Cv0SZZyGgyA

[Edited on 22-10-2015 by zed]

[Edited on 22-10-2015 by zed]

woelen - 22-10-2015 at 22:26

I think that a thread like this become more valuable if unexpected incompatibilities between fairly common chemicals are identified, such as the one between TCCA-like pool chemicals and hypochlorite-based pool chemicals.

Also the mention of unexpected high reactivity of common/easy to obtain chemicals adds value to this thread. At this place I want to mention sodium chlorite (itself being stable and safe on storage, sold as MMS on eBay) being very reactive and giving unexpectedly dangerous interactions with many other chemicals, both in the solid and dry state and in concentrated solutions.

Kagutsuchi - 23-10-2015 at 05:34

Any kind of ammonium compound and chlorates unless you want to make NH4ClO3. It explodes unexpectedly.

Sulaiman - 23-10-2015 at 06:12

Thanks for all the info, I will try to avoid most of the above combinations.
It really is the unexpected bad combinations that I'm concerned with

I guess I have two choices;
mix stuff at will and hope I realise any bad combinations before any accident
OR
Be a little more 'professional' about it and do proper research before 'playing'

(For me it is mostly 'playing' as I have no intention, and too little remaining lifespan, to go professional, just a hobby)

zed - 23-10-2015 at 13:30

"I have been reading through the phosgene threads ... scary!"

I got my personal favorite Phosgene story.

I was trying to break loose a stubborn bolt on my car one time. I wasn't in the lab, so my guard was down. I was alternately heating that bolt super hot, with a torch, and then spraying it with Freon. Seemed OK.....until I thought about it.

The Freon I was using, was an analog to Carbon Tetrachloride.

It was outside, I didn't die, or even get sick. Does that make me less of a moron?

[Edited on 23-10-2015 by zed]

careysub - 23-10-2015 at 14:04

Quote: Originally posted by zed

"I have been reading through the phosgene threads ... scary!"

I got my personal favorite Phosgene story.

I was trying to break loose a stubborn bolt on my car one time. I wasn't in the lab, so my guard was down. I was alternately heating that bolt super hot, with a torch, and then spraying it with Freon. Seemed OK.....until I thought about it.

The Freon I was using, was an analog to Carbon Tetrachloride.

It was outside, I didn't die, or even get sick. Does that make me less of a moron?

[Edited on 23-10-2015 by zed]

You probably know about igniting "canned air" - which produces HF and carbonyl fluoride gas.

And pyrolysis of PTFE (Teflon) produces PFIB (perfluoroisobutylene; perfluoroisobutylene; octafluoroisobutylene; 1,1,3,3,3-Pentafluoro-2-(trifluoromethyl)-1-propene; CAS 382-21-8) which is listed as a toxic agent on Schedule 2 of the Chemical Weapons Convention:
https://www.opcw.org/chemical-weapons-convention/annexes/ann...

The yield for this from PTFE is 40-60%! PFIB is about ten times as toxic as phosgene, making it more toxic than the nerve gas Tabun.

[Edited on 23-10-2015 by careysub]

Dan Vizine - 24-10-2015 at 16:04

Quote: Originally posted by mayko

Chloromethylethers, from the reaction of formaldehyde and hydrochloric acid, have always struck me as a disaster lying in wait for a home chemist.

Am in 100% agreement, the reagents are ubiquitous, and the hazards of this mixture are the scariest thing this side of dioxin. And both reactants are among the small molecules likely to be generated in situ as reaction by-products in other transformations, further complicating the picture.

This mixture is my nomination for the most dangerous, easily accessible mixture around, and one that has undoubtedly killed more people than we'll ever know, across a range of industries.

[Edited on 25-10-2015 by Dan Vizine]

skip - 25-10-2015 at 14:08

Phosphorus pentoxide and wet solvents.