Caustic soda turned intto black slime...
 

I recently obtained a cast metal ashtray that looks like it is cast in
zinc. It'ss actually an admiralty ashtray from HMUDE (Her Majesty's
Underwater Defence Establishment. It had some stains inside it so I
sprinkled some caustic soda crystals in there (since they just
happenned to be at hand) and topped up with water. 30 minutes later, I
was astonished to find the thing full of black slime! Some sort of
chemical reaction, I'm guessing.... but what? Anyone here know enough
chemistry to tell me how/what/why??

Thanks - I'm just curious....!

K

In article ,
(Karl D) writes:

I recently obtained a cast metal ashtray that looks like it is cast in
zinc. It'ss actually an admiralty ashtray from HMUDE (Her Majesty's
Underwater Defence Establishment. It had some stains inside it so I
sprinkled some caustic soda crystals in there (since they just
happenned to be at hand) and topped up with water. 30 minutes later, I
was astonished to find the thing full of black slime! Some sort of
chemical reaction, I'm guessing.... but what? Anyone here know enough
chemistry to tell me how/what/why??

Zinc is amphoteric, which means it will dissolve in both acids
and alkalis. If it is zinc, then you created sodium zincate.
If it is aluminium (or an aluminium alloy -- some look like zinc),
that is also amphoteric.

--
Andrew Gabriel

Karl D wrote:

I recently obtained a cast metal ashtray that looks like it is cast in
zinc. It'ss actually an admiralty ashtray from HMUDE (Her Majesty's
Underwater Defence Establishment. It had some stains inside it so I
sprinkled some caustic soda crystals in there (since they just
happenned to be at hand) and topped up with water. 30 minutes later, I
was astonished to find the thing full of black slime! Some sort of
chemical reaction, I'm guessing.... but what? Anyone here know enough
chemistry to tell me how/what/why??

Mezac probably is the metal, and that would be summat like zinc hydrozde
or oxide perhaps.

Use an acid to cleam it of. Star with vinegare, work our way up thrugh
decsalers and bolied rhubarb leaves to brck acid.




Thanks - I'm just curious....!

K

"Andrew Gabriel" wrote in message


Zinc is amphoteric, which means it will dissolve in both acids
and alkalis. If it is zinc, then you created sodium zincate.
If it is aluminium (or an aluminium alloy -- some look like zinc),
that is also amphoteric.

I think it will be zinc with about 4% aluminium which as we all know is
added to the mix in order to reduce the affect of molten zinc on the
steel molds used in its casting.

How nice to fit another caustic soda thread in before sickmess.

Soda diz gerizzmerzz
Happy new ear
To all the people living in fear.


--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

Michael Mcneil wrote:

Soda diz gerizzmerzz
Happy new ear
To all the people living in fear.

Think I will have a pint of what he is drinking!


--
Cheers,

John.

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"Karl D" wrote in message
...

I recently obtained a cast metal ashtray that looks like it is cast in
zinc. It'ss actually an admiralty ashtray from HMUDE (Her Majesty's
Underwater Defence Establishment. It had some stains inside it so I
sprinkled some caustic soda crystals in there (since they just
happenned to be at hand) and topped up with water. 30 minutes later, I
was astonished to find the thing full of black slime! Some sort of
chemical reaction, I'm guessing.... but what? Anyone here know enough
chemistry to tell me how/what/why??

Zinc will dissolve in hydroxide (alkali) to form zincates [Zn(OH)4]2- and
[Zn(OH)3]-. It is amphoteric, and will also dissolve in acid, to release
hydrogen gas.

Marcus

In message , The Natural
Philosopher writes
Karl D wrote:

I recently obtained a cast metal ashtray that looks like it is cast in
zinc. It'ss actually an admiralty ashtray from HMUDE (Her Majesty's
Underwater Defence Establishment. It had some stains inside it so I
sprinkled some caustic soda crystals in there (since they just
happenned to be at hand) and topped up with water. 30 minutes later, I
was astonished to find the thing full of black slime! Some sort of
chemical reaction, I'm guessing.... but what? Anyone here know enough
chemistry to tell me how/what/why??

Mezac probably is the metal, and that would be summat like zinc
hydrozde or oxide perhaps.

Use an acid to cleam it of. Star with vinegare,

Is that the star in the East ... again ?


--
geoff

"The Natural Philosopher" wrote in message
...
Karl D wrote:

I recently obtained a cast metal ashtray that looks like it is cast in
zinc. It'ss actually an admiralty ashtray from HMUDE (Her Majesty's
Underwater Defence Establishment. It had some stains inside it so I
sprinkled some caustic soda crystals in there (since they just
happenned to be at hand) and topped up with water. 30 minutes later, I
was astonished to find the thing full of black slime! Some sort of
chemical reaction, I'm guessing.... but what? Anyone here know enough
chemistry to tell me how/what/why??

Mezac probably is the metal, and that would be summat like zinc hydrozde
or oxide perhaps.

Use an acid to cleam it of. Star with vinegare, work our way up thrugh
decsalers and bolied rhubarb leaves to brck acid.

No. Zinc dissolves in acid and releases hydrogen gas.

Marcus

Marcus Fox wrote:

"The Natural Philosopher" wrote in message
...

Karl D wrote:


I recently obtained a cast metal ashtray that looks like it is cast in
zinc. It'ss actually an admiralty ashtray from HMUDE (Her Majesty's
Underwater Defence Establishment. It had some stains inside it so I
sprinkled some caustic soda crystals in there (since they just
happenned to be at hand) and topped up with water. 30 minutes later, I
was astonished to find the thing full of black slime! Some sort of
chemical reaction, I'm guessing.... but what? Anyone here know enough
chemistry to tell me how/what/why??

Mezac probably is the metal, and that would be summat like zinc hydrozde
or oxide perhaps.

Use an acid to cleam it of. Star with vinegare, work our way up thrugh
decsalers and bolied rhubarb leaves to brck acid.


No. Zinc dissolves in acid and releases hydrogen gas.


Yes, but slower thn the hydroxides and zincates will.


The idea is to clear rhe sludge and etch teh actual metal a bit to
brighten it up.

Ive used this trick on brass. Works well.



Marcus