hi folks tony fraser here last time we talked i ran you through a very
simple way of doing a specific gravity test to calculate the gold content in your specimens
this time around i'm going to run through another specific gravity test it's a little
bit more complicated but i think it's a lot more accurate and probably a lot more reliable so
we have a gold specimen here we're going to do the test on
to do this for a start you need of course a set of scales some kind of suspension device with
some fishing line so you can suspend your specimen off the scales freely some kind of tub of water
your calculation sheet of course and and of course a trusty calculator so we'll try this piece to
start with and see how it goes so the gross weight on the scale says 110.1 grams all right now the
main trick in doing this test is to make sure that uh you get the same weight as as with the
specimen suspended as you do with the weight on the scale so for start i'm just going to remove
the water and put this suspension mechanism here and zero that out so it goes to zero right very
good now i'm going to tie the gold specimen onto the fishing line here and then we'll suspend it
off the scales again and if everything is going well we should get the same weight
as we did previously
bring it out a bit make sure it's not jagging on anything sometimes it can be tricky to get
exact that's 109.9 we had 110.1 before so 0.2 of a gram that's close enough
right so now what we're going to do is we're going to suspend a specimen in water
i'll get in the water here make sure you give it a bit of a jig up and down make sure that there's
nothing jagging anywhere it's not touching the sides anyway just give it a bounce to make sure
there's no air bubbles or is attached to the specimen and we're going to put it under there
again and suspend it and then we're going to get a different weight based on the buoyancy
of the specimen in which case now we get 72 grams so now with our calculation sheet we're actually
going to calculate the actual specific gravity of this piece so to do that we need to divide the
gross weight of 110.1 grams by the difference between the gross weight 110.1 grams subtract
the wet weight or the weight suspended in water so what we end up with there is divided by 38.9
grams which equals 2.89 so that's the specific gravity of the specimen so then if we uh refer to
our chart here this gives you a list of specific gravities and then the corresponding percentages
of gold 2.89 that's near enough on this chart to 2.9 which gives us a percentage of 11.98
gold so then we calculate 11.98 of our gross weight gives us 13.2 grams of gold
so that calculation shows us that we have about 13.2 grams of gold in this
you know if for all reality i'd call that 13 grams as you can see this
specimen's got a little bit of iron stone in it and a few other bits and pieces so
these the calculations are never going to be 100 accurate but uh 13 grams i'm
actually pretty happy with that so there you go that's how easy it is thank you very much