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86 votes
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How do people know HCN smells like almonds?

The odour threshold for hydrogen cyanide $(\ce{HCN})$ is in fact quite a bit lower than the lethal toxicity threshold. Data for $\ce{HCN}$ can be found in many places, but here and here are a couple ...
long's user avatar
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57 votes
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Brown stains on skin after working with Tollens' reagent

The stains are due to silver nitrate, the reactive portion of Tollens’ reagent. It is very prone to reduction to metallic silver. If you got it on your hands (a clear signal you weren’t wearing ...
Jan's user avatar
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51 votes
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How to properly store acids at home?

First I'd locate the bottle which causes the problem. Usually HCl is #1 suspect, but to be sure you can put a vial with smelling salts (aqueous solution of $\ce{(NH4)2CO3}$) or ammonia in the box with ...
andselisk's user avatar
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42 votes
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How does ammonium nitrate explode on its own?

It is known that ammonium nitrate decompose exothermically when heated to form nitrous oxide and water. This paper1 notes that the irreversible decomposition of ammonium nitrate occurs at the ...
Nilay Ghosh's user avatar
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36 votes
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Neutralizing a sulfuric acid spill

First, why other options are not really the options: A: vinegar, being a weak acid, doesn't neutralize sulfuric acid and only dilutes it; B: solid sodium hydroxide, a strong base, does neutralize ...
andselisk's user avatar
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35 votes

How do people know HCN smells like almonds?

Recognize that a whiff of most toxins, even in high concentration, will probably not kill you. You need a sufficient concentration in your blood - which means you have to actually get a certain number ...
Floris's user avatar
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32 votes

Would the concentration of oxygen around fire increase as we get close to the fire (from the outside)

A fire has no way to directly "draw in" oxygen for it to burn. It consumes what oxygen is in the immediate vicinity of the flame, depleting the air in oxygen compared to the concentration of oxygen in ...
airhuff's user avatar
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31 votes
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Is this poor laboratory safety?

This is more a comment than an answer, but too long for the former.... There are two things for you (and your company) to consider: The SDS of the chemicals being handled - that will give you ...
long's user avatar
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30 votes
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Why can radioactive contamination be spread by people?

Summary: there is not necessarily a contradiction between the two. Radiation is not contagious, and a person who has been exposed to ionizing radiation is not dangerous to other people once they are ...
cbeleites unhappy with SX's user avatar
28 votes
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Emergency shower for nitric acid spills

If you spill nitric acid onto the table, you yourself are unharmed and you can use a cool head to decide what to do next. If the spill is small, pour water on it to both dilute it and dilute the heat —...
Jan's user avatar
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28 votes

How does ammonium nitrate explode on its own?

Ammonium nitrate ($\ce{NH4NO3}$) is widely used in the fertilizer industry and is one of the most concentrated forms of nitrogen fertilizer (35% of $\ce{N}$). At the same time, it has also been widely ...
Mathew Mahindaratne's user avatar
27 votes

Realistic chemical spill accident in high school chemistry class

Collecting together the responses from the comments and Ben Norris's answer and adding one of my own, individual solutions in water of the following chemicals are realistic options for a liquid spill ...
hBy2Py's user avatar
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21 votes
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Is there any substance that's a 4-4-4 on the NFPA diamond?

Diborane. NIOSH gives NFPA 4-4-4-W:
feetwet's user avatar
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18 votes

How do people know HCN smells like almonds?

Gatterman reports (Org. Synth. 1927, 7, 50, as a footnote) that people who smoke regularly have enhanced sensitivity to the smell of cyanide gas, and he recommend smoking while preparing it! Organic ...
Lighthart's user avatar
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17 votes

Realistic chemical spill accident in high school chemistry class

The real high school accidents that I know of involved flammable liquids (ethanol or methanol) igniting. Mishaps in school labs reveal lack of safety (PDF link) Two high school kids burned in lab ...
DavePhD's user avatar
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16 votes
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How can I safely handle a concentrated (fuming) nitric acid spill?

Of course, you’ll want to prevent a spillage as well as possible (making sure the bottle doesn’t fall over etc.) but sometimes you just run into bad luck. Let’s hope that your work bench is at least ...
Jan's user avatar
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16 votes
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Can I eat the lemons after I have used them as a battery?

In a lemon battery, the zinc from the galvanized nail is giving up electrons and transitioning into an aqueous state: $$\ce{Zn → Zn^2+ + 2e−}$$ While zinc is entering the electrolyte, two ...
John Snow's user avatar
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15 votes
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Does latex protect against acids?

There are all sorts of resources for picking the best gloves for handling any given type of chemical. This resource describes latex as being good for protecting against bases, alcohols, dilute water ...
ringo's user avatar
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14 votes

How does ammonium nitrate explode on its own?

First, ammonium nitrate is a kind of mixture between an oxidizer - the nitrate part - and a reducer - the ammonium one. This is at the core of your question. The direct decomposition correctly ...
Alchimista's user avatar
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14 votes

Is powdered acid dangerous?

The state of a compound, solid, liquid, or gaseous is a property which is unrelated to the property / strength of a Brønsted or Lewis acid of said compound. Thus, you can not infer from its physical ...
Buttonwood's user avatar
13 votes
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Metal rod and NMR machine

A little bit about me - I manage a busy research NMR Facility at a leading international tertiary institution. I deal with questions like this not infrequently, and there are some very important ...
long's user avatar
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13 votes

What makes dimethyl compounds so extreme?

This is because of two trivial facts, one from chemistry and another from math: (1) methyl is the smallest organic radical, and (2) it is not uncommon for a function to reach an extremum at the border ...
Ivan Neretin's user avatar
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12 votes

What makes formaldehyde 'safe' or 'dangerous'?

The toxicity of formaldehyde is dose-dependent. The famous saying "the dose makes the poison" is one of the rules of thumb about toxicology. Your body can effectively detoxify small amounts of ...
R. Cabell's user avatar
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12 votes
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Why doesn't Epsom salt dissolved in water act like sulfuric acid?

Well, as you might have guessed, it's the $\ce{H+}$ in sulfuric that is dangerous, not the $\ce{SO4^2-}$. So, Epsom salts, being $\ce{MgSO4}$, aren't very dangerous. In the same vein, table salt ($\...
orthocresol's user avatar
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12 votes
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Should β-mercaptoethanol and anything that touches it be handled only under fume hoods for safety aspects?

β-Mercaptoethanol is not that dangerous a chemical. Yes, you should not drink it, you shouldn’t dip your bare fingers in it, you shouldn’t inhale tons of it and you shouldn’t use it to rub ...
Jan's user avatar
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12 votes
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How does heptafluoropropane suppress fire?

Curt F. is probably correct in his estimate that heptafluoropropane extinguishes fire primarily by physical means. According to an overview by Choy and Fong, 'An Introduction to Clean Agents: ...
Linear Christmas's user avatar
12 votes
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How are N95 masks different from dust masks?

The short answer to your question "What's the science behind the N95 filter?" is that it is what's called a tortuous path filter, removing particulates from a flow of contaminated air by impact and ...
airhuff's user avatar
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11 votes

Is it actually possible to dispose of a body with hydrofluoric acid?

I know this is an old question, but it gets viewed a lot so I thought I would update with the fact that this experiment was actually done on the first Mythbusters Breaking Bad special, episode 206. ...
jheindel's user avatar
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11 votes
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How does sulfuric acid react to heating?

Sulfuric acid, $\ce{H2SO4}$, having an enthalpy of formation of $-814\ \mathrm{kJ/mol}$, is quite stable and won't decompose easily. According to A Kinetic Study of the Decomposition of Spent Sulfuric ...
DHMO's user avatar
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