Elke Blodgett on sat 21 oct 00
forwarded on behalf of Monona
---------- Forwarded message ----------
Date: Sat, 21 Oct 2000 10:40:02 EDT
To: eiblodge@freenet.edmonton.ab.ca
Subject: Re: RE : boiling point of manganese dioxide (fwd)
---------- Forwarded message ----------
> Date: Thu, 19 Oct 2000 16:55:56 +0930
> From: iandol
> Reply-To: Ceramic Arts Discussion List
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: RE : boiling point of manganese dioxide
>
> I think the first thing to do is to set the chemistry straight. My
> references are Greenwood and Earnshaw, 1998 and Levine et al 1979.
>
> Manganese Dioxide decomposes to give Oxygen and Mn304 at about 530 deg
> Celsius, 986 F.
>
> Levine et al give several values of the melting point of Mn3O4 between
1557
> and 1701. I suppose it depends on the method used to determine the value.
>
> There has been very little published in the common tabloid press or
> mentioned on TV news about the replacement of Tetra Ethyl Lead by other
> Volatile Organometallic compounds in the formulation of Lead Replacement
> Gasoline for older automobiles. Whatever is used as a replacement has to
form
> a vapour as it passes through the carburettor mixed with the gasoline. It
is
> the residue of a volatile Organometallic Manganese compound which comes out
> of the exhaust which is the worry. <
>From what I understand, the organic matter gets into the internal combustion
reaction and is burned off. No MMT or organic Mn compounds make it out the
tailpipe. The manganese is released as various oxides just as lead oxides
were released from cars run with the tetraethyl lead additive. The oxides
formed should be related to the amount of oxygen present during combustion.
There are a number of studies done early on when MMT was first being
developed that characterized Mn emissions. There is one review of this data
in which several studies look at the species of manganese compounds released
during the firing which is pretty comprehensive.
Cooper, W.C., "The Health Implications of Increased Manganese in the
Environment Resulting from the Combustion of Fuel Additives: a Review of the
Literature. Journal of Toxicology and Environmental Health 14:23-46 (1984)
Another study worth looking at measured the amounts of manganese to which
taxi workers and garage mechanics were exposed to.
J. Zayed, et. al., American Industrial Hygiene Association Journal, (55)
January 1994, pp. 53-58
I consider this a misleading study overall because the real problem is not
these "below industrial standard" worker exposures but what is going to
happen to these workers and the environment after MMT has been used for years
and the dust in the shops and roadsides is generally contaminated with it.
It is this MN background contamination problem that was the major reason lead
was so destructive as well.
To the study's credit, it does mention that there are no industrial sources
of Mn in Montreal, and yet atmospheric Mn concentrations were 10 times
greater than the natural (rural) background levels. In addition, it mentions
that the City of Montreal has the highest average atmospheric Mn
concentrations when compared with seven other Canadian cities. Maybe this
explains a couple of other things related to Clayart posts.
I present this information because this study was already mentioned by
another Clayart poster in a more favorable light. I did not comment at that
time.
Although the study itself is flawed, there is a good introduction to the
problem which summarizes the accepted information on MMT and has footnotes to
back up every line. Without the footnote numbers included, here's what it
says:
" ... MMT is a yellow volatile liquid with an herbal odor. It is soluble in
water, decomposes rapidly photochemically, and is thermally stable. Its
half-life in sunlight is approximately 15 seconds. The proportion of Mn in
commercial MMT, also called AK-33X (anti-knock agent-33X) or HITEC 3000,
varies from 24.4% to 25.2%. Thus in 72 mg of MMT added to one litre of
gasoline there are 18 mg of Mn. The percentage of Mn emitted from a tailpipe
is influenced by many factors, including the type and condition of the
vehicle and the type of driving cycle. However, an average Mn tailpipe
emission rate of 30% appears to be a reasonable estimate."
"During combustion, the manganese oxides Mn3O4, MnO, and MnO2 are formed.
Particles of manganese tetroxide or hausmannite (Mn3O4), the principal
product of conbustion, generally have diameters between 0.25 and 0.4 um. ..."
> In the posts so far, this is presumed to
> be Manganese dioxide. <
They should be presuming manganese tetroxide.
> If the auto is burning a rich mixture, might it not be in the form of
Manganese Carbonyl?
I think your question is a good one. Although I personally think the
reduction atmosphere could not be strong enough, I think Ethyl Corporation,
which is making manganese-exposed lab rats of us all, should pay for an
updated third party study of MMT emissions in various types of vehicles under
various conditions. And looking for the carbonyl might just be interesting.
Monona Rossol
ACTS
181 Thompson St., # 23
NYC NY 10012-2586 212/777-0062
ACTSNYC@cs.com
answering:
> Ivor Lewis. Redhill, South Australia
>
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