Do You Believe in Density?

My friend Magor suggested I could determine the identity of the mystery metal from our previous furnace melt by calculating its density. Great idea!

The formula for calculating density is: d = M/V. That is, density is equal to the mass of the object divided by its volume.

So I weighed the door plates: 115 g.

Then I tried to measure their volume with the water displacement method. It was a bit tricky since the cup I had wasn't very exact in the measurements it showed, but I figured I could at least get close to a possible density, and then I could compare and see if it was at least in the range of brass (density of 8.5 g/cm3) or aluminum (2.7 g/cm3).

I started with 150 ml in the cup and ended with 174, so that's 24 ml (or 24 cm3). So, door plate density:

d = 115/24

d = 4.79 g/cm3

Hmmm. A not very helpful result. Looks like these door plates are actually Yttrium! (haha.) Whatever this metal is, it seems to be sitting right between brass and aluminum on the density scale. 

Next up was the bits that I thought were aluminum (although upon further reflection they felt heavier in the hand than aluminum should...) 

"Aluminum" pieces: 144 g

Volume: 25 ml or cm3.

So, d = 144/25

          = 5.76 g/cm3

Huh? The suspected aluminum pieces came out slightly more dense than what is supposed to be brass! 

I tried the calculations again with a slightly more accurate graduated cylinder and ended up a little better...

door plates  d = M/V

                        = 115 g / 20 cm3

                        = 5.75 g/cm3

"aluminum"  d = M/V

                       = 156 g /125 cm3

                        = 1.25 g/cm3

😆 At least this time the "aluminum" came out less dense! But both measurements are still far from where they should be for either brass or aluminum, so who knows?

In the end, the method didn't work, for two reasons: I don't have the right equipment to measure volume accurately, and perhaps most importantly, the suspected "brass" pieces are covered in melted bits of the suspected "aluminum", so I can't get clear enough readings with these samples. 

But at least I learned about using this method and now I know that I should at least invest in a finer graduated cylinder!

I bought a slim rod of brass (guaranteed!) and if the weather and air quality is okay, we'll be trying our second melt next weekend. If this melts into a little pool at the bottom of our crucible, we'll know the furnace works.