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Safety...


jowrose
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I recently acquired a whole lot of chemistry equipment (dozens of test tubes, beakers, flasks, etc...) and have since been messing around a little in my basement. I've become interested in acidic reactions, specifically the reactions between HCl (which I get from muriatic acid) and various metals (zinc, aluminum, iron, lead, etc). Theoretically, the products of these reactions should only be hydrogen gas and a metal chloride, but there is always a very strong odor emanating from both the acid, the reaction, and oftentimes the products.

 

So my question is this: are there any safety hazards in these reactions, perhaps involving dangerous gases? Muriatic acid is about 31 percent HCl, plus some water and "baume" (whatever that is). I do have a gas mask, but would that even help?

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To answer your question, that choking gas was HCl vapor. HCl at such high concentrations fumes readily, this can be dangerous. Look at the reaction between a metal and HCl, imagine what it does when you breathe a lot of it in. Obviously not good for you. I would suggest using a fume hood or doing these experiemtns outside to avoid vapor build up. Also, keep in mind that all the HCl gas in the room will corrode most anything. In my room I did some experiments and the quarters i had in my room were shiny on the surface touching the table, but the side fasing the air was corroded

 

@Akcapr, sorry I wasn't fixing your answer, you just got to it before me :)

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Buame refers to the specific gravity, or density, of a solution. I'd suggest double checking that.

Off hand I'd say the reactions you're doing with HCL aren't terribly likely to be very hazardous, if you observe basic safety principles (excellent ventilation, eye wear, gloves).

 

Personally, I would strongly advise against any of this until you have thoroughly researched the experiments you are doing (which you may already be doing) and know exactly what products may be formed. I'd also use reagents that are as pure as possible, as a contamination that you don't factor in could result in some poisonous gas or cargenogenic compound being produced (which is why I'd say it's vital that you build some sort of fume hood, or have a fan and a window nearby).

 

btw, muriatic acid, as far as I know, is just another name for HCl. I'd guess that your HCl solution is just HCL and water. Presumably, you are mixing only three things - a metal, hcl, and water, and if there is nothing else, I'd say you're pretty safe. However, you mentioned an odor. H2 gas is odorless. I don't know what you're smelling, but it may be smart to be cautious.

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Wow, thanks for all the fast replies.

 

Yeah, I was incorrect about the baume. The bottle was kind of old, and I mistook a degree symbol for a percent symbol. Thanks for the correction.

 

Xeluc, I know what you mean with the vapors corroding everthing around. I had a flint sparker for a butane torch and now it's completely useless; the acid vapor started forming some crud (iron chloride i'm assuming) around the whole thing.

 

I guess I really should create some sort of fume hood. That will be somewhat complicated though, as my basement "lab" is not too well situated...

 

Thanks for the replies and suggestions.

 

-john

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When reacting metals with acid there are sometimes strong smells that are not smells of acid i have used to work. At least this is what i have experienced.

 

Some books say that metals contain small amounts of phosphorus, sulfur and arsenic. I suppose these will react with acid and so we get some microscopic amounts of very toxic (and strong smelling) gases. It probably is not especially dangerous because of extremally small amounts but its nevertheless good idea to do such reactions in fume hood.

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Indeed, raivo mentioned it already. Many metals have small impurities, most notably the phosphorous impurity. This gives rise to formation of PH3, which is a very toxic (though non-accumulative) poison.

 

Personally, I would not worry too much, but just to be sure, assure that the room has good ventilation. As long as you only dissolve metals in HCl, things are not that bad, even if traces of PH3 or AsH3 are formed.

 

What you should do, however, is covering the vessels, test tubes and so on with a paper tissue. Not closing them completely, allowing air/gas to escape. This paper absorbs small droplets, thrown in the air, when the acids are bubbling. These droplets enter the air, the water and HCl evaporate and what remains is very fine dust of metal salts and that is a thing which you should worry about. Especially if the metals are toxic (copper, nickel, cobalt). With zinc, aluminium, iron the risks are less. With lead, silver, cadmium and mercury the risks are even larger. Just a little piece of paper tissue over the reaction vessel is a VERY good safeguard against these droplets.

 

For fumes of HCl and NH3, I would not worry too much as long as they do not irritate too much. They are broken down to harmless chloride salts anyway quickly.

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Here is a simple hood design, which Is composed of a cardboard shoe box. One can take the front and back and cut them out so the box now resembles a tube a tube. THen you add 2 computer fans in the back so that when you apple current from an adapter to the fans, they will blow air outwards and suck [fumes] in. The device is then placed in a window, and then the experiment is set in front of the "hood" intake. It worked really good for me. Adding a switch and stuff makes it work nicer, and adding a board to cover up the rest of the open window also helps.This is just an example of what you can make.

fan.JPG

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I made a wooden box with a door and a rack for test tubes, and I think I will simply modify it to have a fan or two at the top connected to a set of pipes that will eventually lead to one of the output vents of my house. I might need several fans along the way to keep the stuff moving though. What should I use for the pipes? probably not steel, I'm assuming. Would PVC be eroded by acid vapor or other somewhat volatile substances?

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