[Wayne]

Wayne asked the Naked Scientists:

Could you tell me where I could get a bottle with a tube attached to its neck
for determining the volume of a coin?  

Thank you. Wayne

What do you think?

[RD]

Putting scores of identical coins in a measuring cylinder half full of water and dividing the increase in volume by the number of coins would be a method of calculating the volume of a single coin.


Assuming the coin is a cylinder then you could calculate its volume by measuring its diameter and thickness.

radius = diameter/2
Pi = 3.1415927

Volume = Pi x radius x radius x thickness

A measuring device called a micrometer would provide accurate values for the thickness and diameter of the coin.

[Wayne]

Hi,
Thank you for your reply.  What you say about assuming the coin is a cylinder is correct, and gives an approximate answer as to the volume, but it is not accurate enough to determine the volume for density measurements.  Coins in general have depressions that are not taken into account when the thickness is measured.

Putting the coins in a measuring cylinder would certainly work for many coins.  Is there a method that would give enough accuracy to determine the volume of one coin to get the density to one decimal?
Thanks,
Wayne

[BenV]

Hi Wayne,

When we did this for Kitchen Science, Dave built his own bottle!

Have a look here:  http://www.thenakedscientists.com/HTML/content/kitchenscience/exp/eureka/

I'm not exactly sure how he made it, but it really can be as simple as a plastic bottle with a biro casing sealed into the side.  We used a drop if washing up liquid to lower the surface tension of the water (so that fewer drops would collect along the inside of the tube.

[daveshorts]

Yes I just drilled a hole in the side of a bottle and stuffed a piece of silicon rubber tube in the side. I think it took a bit of bath sealent to seal the gaps.

[Jroger]

I struggled with this myself. I initially thought about using a contact lense dropper bottle on it's side, and cutting a hole in it. Then I discovered the specific gravity test which is actually much more accurate, imho. I found this blog post on it and copied what he did, it worked quite well. A mistake I made was I thought I could use a cylinder formula, but apparently you can't. The link is below

newbielink:http://bullionultrasound.com/blogs/news/6655282-gold-coin-mass-volume-and-density-verification-1oz-american-eagle [nonactive]

[cheryl j]

Cant you just use any small graduated cylinder, fill it with water and measure the amount it increases when you add the coin?

[RE.Craig]

If you know what the alloyed composition of the coin is you should be able to work out it's volume by weight. A complicated but very interesting evening with a calculator and composition tables from the Royal Mint. I discovered that penny's up to 1992 were composed of = Bronze (97% copper, 2.5% zinc, 0.5% tin) - until September 1992. Pennies up to that date are in fact materially worth at this time [Feb 2013] 3 pence sterling! Pennies after this date are copper plated steel and worth materially 1 pence for 168 of them which explains why I pulled out a conglomeration of worthless corroded steel out of a coin bottle recently!!! What was more surprising is that the UK penny is only legal tender in amounts up to 20p !!! Rip of Britain is alive and well     

[Bored chemist]

If you have a half decent balance you can measure the volume of an object which is denser than water (like a coin) accurately and easily.
Whether the OP is still listening for replies 4 years later is another matter.