C. van Riemsdijk on mon 25 nov 96
>Potassium dichromate and bichromate are both extremely toxic in their raw
>state.
Help, I always thought they are the same, Bi and Di both meaning two.
Have I always been wrong?
Carolien, in Haarlem the Netherlands, and very confused.
Craig Martell on tue 26 nov 96
Hi Carolien: I purused my arsenal of literature on glazes and materials and
can find nothing that differentiate Potassium Bichromate from Dichromate. Bi
and Di do denote that two of something(chromium) are present. You are
probably correct in assuming they are the same thing. I wish I could provide
both of us with a better answer.
Kind Regards, Craig Martell-Oregon
BobWicks@aol.com on tue 26 nov 96
Hi Carolien:
I read your note re: the chromate compound. Both Potassium bichromate and
potassium dichromate are exactly the same thing. When bichromate was first
used they went by that name, however later for some reason unknown to me they
started calling it Dichromate. Use it very carefully and NEVER spray it on
projects. One of my college student used it to make paper photo sensitive
and wanted to spray it using a fume hood. Needless to say that was bad news
as he developed a severe case of chemical pneaumonia. In some cases where a
person is sensitive bichromate causes a very severe dermatitis. I have been
working with potassium bichromate in photo sensitive projects since 1954 and
if you are careful you will have no trouble.
WHampton@aol.com on wed 27 nov 96
Bob,
Did your friend use a mase when he sprayed the chemical? I have a friend
that sprays it and has no problems but I know she is very careful using
resperator, etc.
Thanks,
Wendy from Bainbridge Island WA
kevin_hulmes@uk.ibm.com on thu 28 nov 96
Carolien and Craig supposed that Potassium Dichromate and Potassium
Bichromate are the same thing, and they are right. The formula is
K2Cr2O7, and (as somebody else has remarked) it is a powerful oxidising
agent and can explode when heated with finely powdered oxidisable
material. It's quite spectacular when heated on its own in a test tube,
glowing and sparkling while producing far more than its original volume
of dark green Chrome Oxide. Take great care if you try this, only use a
teaspoonful, spread a large protective sheet around you and don't breathe!
A lot of scientific terminology comes either from ancient Latin or Greek
roots, and as far as poor old K2Cr2O7 is concerned, there seems to have
been a little indecision. (Also applies to a number of other
substances.)
The prefix Bi comes from Bis, the Latin for twice; whereas Di comes from
Dis, the Greek for twice. As the name Chromium derives from the Greek
word khroma (colour), Dichromate seems the most consistent, and is the most
widely used.
Isn't it amazing how much useless information your brain picks up as you
trawl through life! Yet I have difficulty remembering what I did last
weekend!
..... Kevin
*--------------------------------------------------
* INTERNET: kevin_hulmes@uk.ibm.com
* Phone/Fax/Msgs (0)1926 887003 (UK)
*__________________________________________________
Kirk Morrison on fri 29 nov 96
On 28 Nov 96 at 11:07, kevin_hulmes@uk.ibm.com wrote:
> ----------------------------Original message----------------------------
>
> Carolien and Craig supposed that Potassium Dichromate and Potassium
> Bichromate are the same thing, and they are right. The formula is
> K2Cr2O7, and (as somebody else has remarked) it is a powerful oxidising
> agent and can explode when heated with finely powdered oxidisable
> material. It's quite spectacular when heated on its own in a test tube,
> glowing and sparkling while producing far more than its original volume
> of dark green Chrome Oxide. Take great care if you try this, only use a
> teaspoonful, spread a large protective sheet around you and don't breathe!
>
> A lot of scientific terminology comes either from ancient Latin or Greek
> roots, and as far as poor old K2Cr2O7 is concerned, there seems to have
> been a little indecision. (Also applies to a number of other
> substances.)
>
> The prefix Bi comes from Bis, the Latin for twice; whereas Di comes from
> Dis, the Greek for twice. As the name Chromium derives from the Greek
> word khroma (colour), Dichromate seems the most consistent, and is the most
> widely used.
>
> Isn't it amazing how much useless information your brain picks up as you
> trawl through life! Yet I have difficulty remembering what I did last
> weekend!
>
> ..... Kevin
>
Yep, from what I have seen at work, what is slowly happening is that
the di's are becoming the prefix of choice with words of Greek origin
unless their is a chemical variation of two then you get all sorts of
mishmash, and the bi for word of Latin orgin.....Remember what A.C.
Doyle had Holmes say about to much useless information rattling around
in the old attic.
BobWicks@aol.com on sat 30 nov 96
No my student did not wear a mask, but the fume hood should have been
adequate. The results were freightening, so treat potassium bichromate with
great care.
Bob
Lynn Curran on sat 10 may 97
Hi, I am curious as to the toxicity of potassium bichromate, one ingredient
in a plum color, pumice ^6 glaze, I've been using for the last 15 years....
Suppliers have stop carrying it, and offer no info. I have researched and
have only
found potassium chromate listed in several references.
Any info would be appreciated?
Lynn Curran
Random Pottery
Newmarket, NH
j.kelly@genie.com on mon 12 may 97
Reply: Item #2821981 from CLAYART@LSV.UKY.EDU@INET#
I hope that you show more than mere curiosity about Potassium
Bichromate, aka Potassium Dichromate. For your own personal health,
take a look at what Daniel Rhodes said in his book, "Clay and Glazes
for the Potter" Revised edition, Chilton Book Company, 1973 :
on page 210, he says about Chrome oxide in general, it "is quite
volatile at cone 6 or above..." He says further, "Chrome Oxide may be
used as the green oxide of chrome...or as Potassium Dichromate. This
latter material, however, has the disadvantage of being soluble [in
water] and poisonous."
Potassium Dichromate also has a reputation of sensitizing some people
to Chromium in any form. It was used as an oxidant in photographic
processing for may years and some photographers had to change their
processes.
When I was a practicing chemist, many years ago, we all handled this
stuff quite freely. If I were in the lab today, I would be much more
cautious. Now that I work with clay and glazes, I tend to avoid
Chromium as far as possible.
Our resident toxicologists should have some quantitative data to
offer.
John Baymore on mon 12 may 97
......
Hi, I am curious as to the toxicity of potassium bichromate, ....
Lynn Curran
Working from the "brain database" here....... as I recall it, potassium
bichromate (dichromate) is, like all chromium compounds, a carcinogen. It
also causes skin ulceration and severe irritation to nasal membranes. I
think the OSHA airborn TLV's are the same as for lead compounds....although
not sure on that one. I seem to remember some other particular
peculiarities that make it QUITE toxic, but can't remember off hand.
I would hope that Monona picks up this one.
Best,
............................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
603-654-2752
JBaymore@COmpuserve.com
Tom Colson on tue 13 may 97
All-
John Baymore wrote:
>Working from the "brain database" here....... as I recall it, >potassium bichro
Hey John, looks like you need to take that database down for
maintenance! All chromium compounds are NOT carcinogens. Cr in the 6+
oxidation state, as in chromates, IS a carcinogen. The chrome on your
Buick's bumper or in the stainless steel untensils we all use is NOT.
With the incredible number of materials we all work with, the only way
to get accurate health and safety information is to consult a reliable
source, like an industrial hygenist/toxicologist or the literature
created by same.
I not trying to give John a hard time, it's just that "sort of accurate"
statements lead us to discount real hazards. More and more we also
overstate hazards where the data just doesn't support it. Hopefully,
with the explosion in information technology, we will all soon have
access to authoritative sources on these issues to clear away the fog.
Off the soapbox...
Regards,
Tom
--
Tom Colson tcolson@aimnet.com
Tiles On The Web: http://www.aimnet.com/~tcolson/webtiles.htm
The web site for handmade and historic ceramic tiles.
M Richens on mon 19 may 97
In article <33788D7C.273C@aimnet.com>, Tom Colson
writes
Hi Tom,
>Hey John, looks like you need to take that database down for
>maintenance! All chromium compounds are NOT carcinogens. Cr in the 6+
>oxidation state, as in chromates, IS a carcinogen. The chrome on your
>Buick's bumper or in the stainless steel untensils we all use is NOT.
>
I think that you'll find that the chrome on your bumper is in fact a
nickel coat. In the UK at least chrome plating is now only used in
military applications due to the problems with dealing with the
chemicals needed to lay down the chrome (ie cyanides).. I suspect that
john was just being a little loose in his category of 'chrome' when he
meant the salts and oxides rather than the chrome metal. I have found
that if you overdo the use of chromeoxide in glasses then you can end up
with a finish that will smear leaving chrome stains everywhere. Hardly
a healthy effect.(this was above 5% by weight though). In smaller
quantities you get greens and yellows and pinks though.
Just handle it sensibly and don't get casual. I've dealt with most
compounds including arsenic ones and Hydrofluoric Acid (Very Nasty
stuff..) over many years but like all ceramic people and metallurgists
you wear the neccesary kit and you wash your hands before doing
_anything_ else.
Max
--
Max Richens max@richens.demon.co.uk +44 (0) 1925756241
Enamel Consultant - Ceramist - Analyst programmer
Software for Batch Formulation and Millroom control.
LTFCURRAN on wed 21 may 97
Thanks to all regarding for the response to my query.
I've taken on a new attitude towards my glazing, and especially what
glazes
I allow my students to use. Don't plan on continuing this glaze, a
purplish,
plum, pumise based glaze. I'll miss it.
Here's to clay!
Lynn Curran
Random Pottery
Newmarket, NH
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