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86 votes
Accepted

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 ...
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68 votes
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Do all salts taste salty?

No. There are sweet, bitter, and various other salts. (Likely, there are tasteless salts too). Pure salty taste is as far as I know exclusive for table salt, though I wouldn't bet on it. Lead and ...
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55 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 ...
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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 ...
  • 35.8k
42 votes
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Acid Accident Treatment

My Lab First Aid book$^{*1}$ tells the following: The local therapy mainly consists of the instant, intense rinsing (at least 10 minutes) with tap water (ideally 15 to 20 °C). Don't try to ...
41 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 ...
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36 votes

Do all salts taste salty?

Saltiness is perceived when alkali metal enter taste buds. From wikipedia: Saltiness is a taste produced primarily by the presence of sodium ions. Other ions of the alkali metals group also ...
  • 1,770
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 ...
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34 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 ...
  • 35.8k
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 ...
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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 ...
  • 11.8k
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 ...
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 —...
  • 64.8k
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 ...
26 votes
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What are the fumes that form above liquid nitrogen?

The visible fog that forms when liquid nitrogen is poured into an open container is almost entirely water fog: the boiling nitrogen chills the air above it, causing the humidity in the air to condense ...
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26 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 ...
  • 16.9k
21 votes

Why did the salt on the skin of my turkey react with the aluminum foil it was touching?

If you don't mind, I'll start with a more colloquial and hopfully not to lengthy explanation: Precious metals, such gold, do not corrode under "household conditions", others, such as iron or ...
20 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:
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18 votes

Acid Accident Treatment

Speaking from experience. Minor spills (drops) on skin of concentrated nitric or sulfuric acid are nothing to speak of. Wash them off with plenty of water for a minute or two and you are fine. I'm ...
  • 20.9k
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 ...
  • 6,518
17 votes

Do all salts taste salty?

permeakra is quite right with his counterexamples of salts that don't taste purely salty, but I'd like to expand on why. We haven't fully identified and elucidated the receptors involved in taste, but ...
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 ...
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16 votes
Accepted

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 ...
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15 votes
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Why are lab coats required in chemical laboratories?

It is protection. It should be worn whenever you work with potentially dangerous chemicals. In German, it is even called (part of the) persönliche Schutzausrüstung, i.e. personal protective gear. Lab ...
  • 64.8k
15 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 ...
  • 64.8k
14 votes

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

Here in Mexico, a guy was arrested a couple years ago for "dissolving" more than 300 bodies killed by the cartels. They found 55-gallon drums around town with a sludge in it, usually with a note to ...
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14 votes
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How to dispose of pure potassium

In a suggested lab, the RSC recommends using propan-2-ol: If there is any unused potassium remaining at the end of the experiment, remove it with the tweezers and place it in a beaker containing ...
14 votes
Accepted

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 ...
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