MYSTERY OBJECTS

[PanBiker]

It's a fire extinguisher that I think used some quite obnoxious and nasty chemicals which a re now banned for such use.

[Big Kev]

It's a fire extinguisher that I think used some quite obnoxious and nasty chemicals which a re now banned for such use.

Was it pyrene?

[Gloria]

Fire extinguisher.

[Stanley]

Yes you're all right.

Fire extinguisher fluid ‘Pyrene’ contains carbon tetrachloride CCl4 . When carbon tetrachloride is heated, it decomposes and emits fumes of toxic phosgene (COCl2) as well as hydrogen chloride (HCl) . The dense layer of carbon tetrachloride vapours forms a protective layer on the burning place or burning object and blocks the supply of oxygen or air.
It is also used in large quantities for manufacturing refrigerants and propellants for aerosol cans. It is also used in the synthesis of chlorofluorocarbons and other pharmaceutical manufacturing.
Scientific study provides evidence that exposure to carbon tetrachloride causes liver cancer in humans. If inhaled, it causes dizziness, lightheadedness, nausea and vomiting, which might result in permanent damage to nerve cells. These effects can also lead rapidly to stupor, coma, unconsciousness or death. Exposure to CCl4 can make the heartbeat irregularly or stop. It can also cause irritation to the eyes on contact. If carbon tetrachloride is released into the air, it rises to the atmosphere and depletes the ozone layer. Due to its environmental concerns and its poisonous nature, its use has gradually declined after 1960′s .
The extinguishers had another disadvantage. Carbon Tetrachloride was a very effective dry-cleaning agent and the crews of the buses soon realised this and consequently many extinguishers were found to be empty when needed!
Next object?

[Stanley]

What is it?

[Big Kev]

They look like the jaws of a bolt cropper.

[Stanley]

Spot on Kev. Spare jaws for mine....
Next object?

[Tizer]

The extinguishers had another disadvantage. Carbon Tetrachloride was a very effective dry-cleaning agent and the crews of the buses soon realised this and consequently many extinguishers were found to be empty when needed!

And it was the component in products widely sold `over the counter' (OTC) for cleaning clothes etc. People our age will all have used it. It was also used as a solvent in chemistry laboratories but by the time I started work in a research lab my supervisor had banned its use. He wisely banned chloroform too. The only difference is carbon tetrachloride (tetrachloromethane) has 4 chlorine atoms whereas chloroform ((trichloromethane) has 3. Another widely used solvent/cleaner was trichloroethylene. Typical brand names for these chlorinated hydrocarbons included Dabitof and Thawpit.

[PanBiker]

When I started work, switch cleaner used to be carbon tetrachloride based, shortly replaced by a more innocuous mix. For general PCB work I always favoured Isopropyl Alcohol, excellent for cleaning solder joints and varnish from PCB's. We had PCB varnish spray to apply after working on boards.

[Steeplejerk]

Trichloethylene always loved that smell in Johnsons dry cleaners

[Steeplejerk]

Think I may have got that wrong and it's used to degrease before painting

[Stanley]

Yes Tom, a typical de-greasing plant when I was a lad was an open tank of Trichloroethylene with a triple row of refrigerated pipes running round just over the surface level. These condensed most of the vapour as it tried to escape, if I remember correctly it was heavier than air.... You degreased stuff by dipping it in the 'trikes'. I remember my dad telling me that they had to take the man who ran the tank off the job because he was deliberately inhaling the vapour to get high. This was seen as amusing rather than dangerous. Things have change somewhat!



What is it?

[Mags]

A piece of brass.......

[Stanley]

Sorry Margaret but no.... Have a closer look at it....

[Gloria]

A pendulum clock weight?

[Stanley]

Yes Gloria, well done!
Now we need another one.....

[Stanley]

What is it?

[Gloria]

Is it a decorative lawn edging?

[Stanley]

No Gloria. It's made of sheet metal and the tongue is about two inches wide....

[Big Kev]

Is it a 'form' or guide for making something?

[Tizer]

Is it for hammering into wood or stone to start a split?

[Stanley]

Kev is on the right track. It's a template for turning something..... Clue, big and connected to steam engines....

[Stanley]

If there is no movement by dinnertime I will come clean but think of the biggest object and look at the shape of the template......

[Gloria]

Is it a template for the grooves to take the rope on the main drive wheel?

[Stanley]

Exactly right Gloria! Well done.
Now we need another object.....