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Old 2006-10-13, 08:04   #78
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Quote:
Originally Posted by ewmayer View Post
Since my college chemistry classes, I've always wondered who the poor soul was who was the first to discover that colorless HCN gas "smells like bitter almonds." Unless they were fortunate enough to catch only a slight non-fatal whiff, I keep envisioning a Pythonesque "well, he wouldn't have *written*, 'Smells ... like ... bitter ... almonds ... aaaaaaaaaaaaaaarghhhhh ...' before he died, would he?" scenario.
I've smelled HCN on several occasions and it does, indeed, smell of bitter almonds.

Have you ever smelled hydrogen sulphide? It's what rotten eggs smell of.

H2S is significantly more toxic than HCN.

I never really understood why there is so much fear of HCN and of cyanides in general. They are just another class of fairly toxic compounds. There are many many much nastier chemicals out there. Organo-tin compounds, for instance, used in anti-fouling paints for boats.


Paul
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Old 2006-10-13, 16:11   #79
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Originally Posted by xilman View Post
I never really understood why there is so much fear of HCN and of cyanides in general.
Yes, looking more closely at the Wikipedia page I linked to it cites danger levels of hundreds of PPM for HCN, which is really quite high - like I said, when we were warned about this in freshman chemistry, the lab assistant made it sound like the stuff was nerve-gas fatal.

So, sniff any tetrodotoxin or brevetoxin lately?
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Old 2006-10-13, 17:17   #80
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Quote:
Originally Posted by xilman View Post
I've smelled HCN on several occasions and it does, indeed, smell of bitter almonds.

Have you ever smelled hydrogen sulphide? It's what rotten eggs smell of.

H2S is significantly more toxic than HCN.

I never really understood why there is so much fear of HCN and of cyanides in general. They are just another class of fairly toxic compounds. There are many many much nastier chemicals out there. Organo-tin compounds, for instance, used in anti-fouling paints for boats.


Paul

Well, Hitler poisoned his Alsatian dogs as a test to see how potent it was if used on himself, his generals and his recent wife. Eventually, he preferred his Mauser pistol.

Yes I have had liberal doses of H2S in my high school days. For some reason we always had it on tap in big jars as it was easy to produce.
It did smell of rotten eggs.

There is a theory that brief sniffs of bad smells opens the brain cells and increases alertness. There are a variety ways of doing this but I leave it to others to imaginatively experiment.

In India a common cure for epileptic seizures is to put a slipper on the patients nose to revive the person, and from my own personal experience of effecting a cure, it does work. But be wary, as certain body odours can be addictive to the nasal passages.

IN Art galleries there is sometimes a foul smell from Large Paintings due to H2S from the paint. Many of the so called miracles of crying Madonna's is due to the moisture in the air converting SO2 into H2SO3
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Old 2012-03-14, 00:30   #81
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Happy Uranus Day! Today marks the 231st anniversary of the astronomer William Herschel first observing Uranus.

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Originally Posted by Uncwilly View Post
For what it is worth, there are several other suggestions from various places that other cultures may have in fact seen Uranus. It is with in the limits of a sharp eyed person under very good conditions.
I personally have seen Uranus with out optical aid a few years ago. In a dark sky location, I used averted vision to see it. It was in the exact right spot as the chart and it had just enough color to not be a star.
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By this argument, Neptune was discovered before Uranus. An intelligent system (Galileo) found the planet close to Jupiter in the early 17th century and one of his drawings of it has survived. Needless to say, he thought it was a star and although he found it, he didn't recognize it.

Flamsteed found Uranus in the 18th century. He included it in his star catalogue (as 5 Tauri if I remember correctly --- I haven't checked) but failed to recognize it as a planet. The latter is quite inexcusable. If he'd gone back to check his measurements some time later he would have found it had moved in the interim, a behaviour for which the fixed stars are not noted but which planets most certainly are.
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Old 2012-03-14, 02:00   #82
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Quote:
Originally Posted by mfgoode View Post
There is a theory that brief sniffs of bad smells opens the brain cells and increases alertness. There are a variety ways of doing this but I leave it to others to imaginatively experiment.
Perhaps attempting to observe Uranus is one way to expose yourself to such brain-alerting vapors.

[Sorry about the sophomoric tasteless joke, but somehow the juxtaposition of Uncwilly's Herschel-anniversary post with this post by the late mfgoode was too curious pass up].
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Old 2012-03-14, 07:55   #83
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Quote:
Originally Posted by xilman View Post
Have you ever smelled hydrogen sulphide? It's what rotten eggs smell of. H2S is significantly more toxic than HCN.
When I was in highschool we used to play nasty jokes on other colleagues. We could buy aluminum powder from chemical shops (used for painting, for pyrotechnics, etc), well everybody knew how to mix it with lead tetroxide (or minium - by the way, here is where the English math related "minimum" or not-math related "miniature" is comming from!) to make flash powders or firecrackers, all the materials were very easy to buy from chemical or plumbing shops. I had a real "arsenal" of small plastic recipients filled with all kind of chemicals. Of course, sulfur and carbon powder were not missing, as basic components of gunpowder. We did not have the "regulations" as existing today, and every one of my friends were able to make small firecrackers and petards for different festivals or amusement purposes. But noone knew, except me, that you can mix aluminum powder with sulfur and burn them together to make aluminium sulfide. Maybe some of them discovered it, same way as me: mixing the powders together and try to ignite them, with the goal to discover some new type of flash powder.

The procedure is very easy, you mix about 10-20 grams of each of the powders (aluminium and sulfur) together, make a small cone (as a small "hill" or "volcano") and using a long match or a stick (about 20 cm, to protect your hand) set it on fire (ignite it in a side). It does not explode, and in fact it is very difficult to ignite it, that is why it presented no interest as flash powder, and nobody bothered with it. If you at least succeed to ignite it, it will burn moderately, exhausting a lot of heat, the temperature goes over 1000 degrees, and it can cut through the steel tray, so you should be careful to have a stone or brick under (see aluminothermy). I tell you from my personal experience. I spent ages trying to make "bengal fires", hehe, the holidays and weekends were a wonderful time when I could go home and make some new experiments... well, this thing was no use for firecrackers, no one was interested in it. After the small mound burned, the "leftover" was the aluminum sulfide. It looks like hard gray stone, you can do nothing with it, except break it with a hammer. When I first discovered it, I said to myself, well, it is not good for salutes, let's see if it is good for some percussion cracker, so I took the hammer hit it hard, but it broke into very small grains (like a car window, but smaller, 2 cubical millimeters each). It did not explode, it did not make any loud noise... well, I was ready to get rid of it. Then, when I put my fingers on it, I notified the smell..

What the hack, I said, and looked into the book... There was no wikipedia that time . Then the "brilliant idea" rooted under my hair..

The aluminum sulfide is very water-hungry. It will react with the water from the air, and with the water from your skin sweat, if you touch it with your fingers, producing lots of hydrogen sulfide by the reaction: Al2S3 + 6 H2O = 3 H2S + 2 Al(OH)3.

So, once you have it, you should manipulate it with the tweezers only, and keep it dry. A small air-tight plastic recipient like the one for pills is perfect.

How to use it? well, here the LaurV's genius come into play .

When you are in highschool and live in a boarding campus and your roommates got angry on some guys from another room, you can take a small grain (2 cubical mm is enough) of the well-guarded secret substance and put it in a small piece of tissue paper. Then you colloquially go to the other room, to ask for some homework help, or whatever... In the mid of the discussion, you - like any human being - feel the need to cough or blow your nose, or just take out the tissue paper from the pocket, spit on it an put it on the rubbish basket. Then you discretely live the room no later then two-three minutes after. The "fart-bomb" will "detonate" in about this amount of time, to a level when noone would be able to stay in the room. The nasty part is that no one can tell where the smell is coming from, and they start accusing each other, sometime fights burst open, etc., eventually they start opening the doors and windows and taking things out of the room, etc. Even if they take out the rubbish basket, they can't find the source of the smell (which is long gone from the basket, and already impregnated in different objects in the room) and the smell won't disappear for hours.

I remember once a roommate dropped "the bomb" in another room. The guys from the other room were so confused, they didn't know what is going on, but they realized that my colleague is to blame for it. They went to the principal and requested some punishment for my colleague, who "went to their room and fart so hard they need to keep the door and windows open for an hour". It was an investigation and everybody negated, and we all (including the principal and the homestay teachers) laughed so hard, and the other guys were so ashamed... and at the end everybody rolled with laugh..

Last fiddled with by LaurV on 2012-03-14 at 08:21
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Old 2012-03-14, 08:23   #84
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Quote:
Originally Posted by LaurV View Post
The "fart-bomb" will "detonate" in about this amount of time, to a level when noone would be able to stay in the room. The nasty part is that no one can tell where the smell is coming from, and they start accusing each other, sometime fights burst open, etc., eventually they start opening the doors and windows and taking things out of the room, etc. Even if they take out the rubbish basket, they can't find the source of the smell (which is long gone from the basket, and already impregnated in different objects in the room) and the smell won't disappear for hours.
In my student days a similar practical joke was to tape the wrapper from a Camembert or the like to the rear of a radiator. A much slower but much longer lasting effect.

For instant-acting amusement we'd use "nitrogen triiodide" as it is commonly but not strictly correctly called.


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Old 2012-03-14, 08:42   #85
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Jeeziz, the rules at my boarding school were so freakin strict, and they keep getting worse every year. (Then again, all the rules they have now were created because someone in the past broke them.)
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Old 2012-03-16, 08:26   #86
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Quote:
Originally Posted by xilman View Post
In my student days a similar practical joke was to tape the wrapper from a Camembert or the like to the rear of a radiator. A much slower but much longer lasting effect.

For instant-acting amusement we'd use "nitrogen triiodide" as it is commonly but not strictly correctly called.


Paul
Limburger works even better. I've been in an exam that got scrapped about two-thirds of the way through because of a mysterious stink; turns out it was Limburger cheese strategically placed in the physics lab. Wasn't much fun having to retake (a different form of) the exam the next week.

Last fiddled with by NBtarheel_33 on 2012-03-16 at 08:27
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Old 2012-03-16, 10:41   #87
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Quote:
Originally Posted by NBtarheel_33 View Post
Limburger works even better. I've been in an exam that got scrapped about two-thirds of the way through because of a mysterious stink; turns out it was Limburger cheese strategically placed in the physics lab. Wasn't much fun having to retake (a different form of) the exam the next week.
Limburger is indeed much better, both for eating and for using the wrapper afterwards.

Unfortunately, Limburger is especially difficult to get hold of in these part.
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Old 2012-03-16, 12:29   #88
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I have a second hand account of someone leaving a 'road apple' in a rival dorm. It was left in a bit of foil, with some hole, in an oven on the lowest setting. It was a gift for the dean's arrival later that day.
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