Andy P wrote:
> "Dr. William H. Pence" <
[email protected]> wrote
>
>
>>Perhaps if you had examined the rest of the page you might have noticed some of the other
>>information about hazardous chemicals. For example, the table of low flashpoint chemicals includes
>>includes acetone, with appropriate cautions. The first list of hazardous chemicals lists the
>>primary hazards that one might encounter in the laboratory which are associated with the listed
>>chemicals, not all of them. Those hazards are the ones associated with personal injury, not lab
>>destruction. And, in truth, vapor inhalation is usually what one would worry about with respect to
>>quantities of acetone.
>
>
> Right, so inhaling a bit of acetone in an open laboratory is more of a hazard than inadvertantly
> setting yourself on fire because nobody told you it was flammable.
Actually, yes. Bulk quantities of flammable solvents are stored in fireproof cans with mesh fire
damp screens and smaller quantities are stored in glass or plastic containers with FLAMMABLE labels
on them. When I was taking sophomore organic chemistry we still used Bunsen burners (that was 35
years ago-surely they are using heating mantles now) we were certainly aware of what was flammable
and what was not, and we were extremely careful. I suspect that open flames are not common anymore.
But you are begging the question; the web page clearly highlighted the hazard of the low flash
point of acetone, as well as other chemicals which shared that hazard. The fact that they listed
the personal effects of the chemical in one place and the physical hazards in another does not
render them
I did flick through the rest of the website and you don't
> need to know anything about chemicals to appreciate that giving inconsistent and confusing
> information is very bad practice.
Could you cite some specific instances of confusing information?
>
>
>>We do not usually describe the actions of strong acids and the like as corrosive when applied to
>>human skin, irritant is the term used. Corrosion is a term usually applied to metals.
>
>
> "We" as in who? Certainly not anyone with any knowledge of the legislation affecting the packaging
> or use of chemicals. Telling people something is irritant when in fact it will cause severe
> burning is negligent in the extreme.
You think so? I don't agree. A solution of 0.01 M HCl is not likely to burn you very badly. A
solution of 3 M would cause much more irritation. You add vinegar to your salad but glacial acetic
acid is quite a bit stronger. You use hydrogen peroxide to cleanse wounds but we also use it as an
oxidiser for our chemical lasers.
Detailed information on hazardous chemicals is available in the Material Safety Data Sheets, which
should be readily available in any laboratory. There you will probably find the detailed information
you seem to desire.
>
>
>>Back to the original topic of this exchange of views, the reason we add acid to water is because
>>of the large, exothermic heat of solution for these chemicals. When you add acid to water the acid
>>molecules are immediately solvated and a large amount of heat is liberated. This can cause
>>spattering; fortunately if you have added acid to water most of what is spattered is water or
>>dilute acid.
>
>
> "Solvated"? is that a proper word?
Actually, yes. A solvent will solvate, or produce a sphere (so to speak) of solvation
around a solute.
>
>
>>Should you, on the other hand, add some water to Con Sulphuric acid, the heat liberated as the
>>water solvates the H2SO4 causes it to get hot very quickly, turning it to steam (so to speak-
>>worst case) and spatters the Con Sulphuric around.
>
>
> Yes, but still just sulphuric and not every concentrated chemical or even every concentrated acid
> which was my original point.
Your original point is incorrect. If you look at the CRC handbook of Chemistry and Physics, you will
find a table of Heats of Solution for various substances. Strong acids have large exothermic
reactions upon contact with water; some strong bases share this characteristic, others do not.
Crystalline NaOH is strongly exothermic. The steam explosion when a water molecule jumps on the
loosely held proton of a strong acid is something to see.
>
>
>>For this reason I used to teach my students (and now tell my techs) "Acid to Water". Vis a vis
>>your concerns about pouring, try using a glass rod to pour acids. You will find that it eliminates
>>dribbling.
>
>
> I did try the glass rod tip once but it didn't work for me. Obviously needs practice. I'm sure
> more people have experienced spilling milk when pouring it into a cup of coffee than the coffee
> splashing out. Couldn't decide whether or not you were just trolling but my girlfriend's away and
> there's not much on telly. Anyhow if you are really in the position of teaching people chemistry
> please go and learn some basic health & safety issues.
Actually I don't teach people chemistry anymore, I'm president of an electro-optics firm. Perhaps
you could enlighten me as to your wealth of experience in this area? I'm always looking to enhance
my laboratory safety program. Perhaps my Safety Officer could contact you as to proper handling and
storage of hazardous chemicals?
I begin to understand Mr. Brandt's frustration.
Oh, and regarding the original poster's questions, I have found that cutting out the seatpost with a
hacksaw blade held in a fixture to work well, though it is painfully slow.