Someone asked on the school forum what is chemistry?

"For me it was the reaction involved making a cup of tea for my wife this morning. You know when you put milk in first and it does not draw the tea as well as when you steep it in boiling Water before the milk.

i always imagined the milk coated the tea to stop it leaching. silly me. And this morning thinking about it chemically. I now imagine the Milk containing its lactic acid and amino protine acids and the Tea is an alkaloid. The result is a PH change and reduction in the chemical reaction rate.

i tried to "Express it" (pun again)..

H2O + C3H6O3 (lactic acid)= PH 8.0 + H2O + T ( = PH 6.0 x 0.5 = 7.0

leaving a balanced PH of 7.0

It was fun to do, and i learned something new on the way, and got in the good books with my wife, as a bonus!"

The above nonsense is a forced equation and not correct. Close, but not accurate.

To measure golds calorific value.

The equation we can use to see if a sample is real gold or fake is its heat capacity is actually very simple.

"A 1.6-g sample of a metal that has the appearance of gold requires 5.8 J of energy to change its temperature from 23 C to 41 C. is the metal pure gold?"

Source: Chemistry (2008) Steven Zumdahl | ISBN-10: 0547125321 | ISBN-13: 978-0547125329 |

Given:^T = 41 C - 21 C = 18 C

Using the data given, we can calculate the value to the one for gold 0.13 J We know that.

Q = s x m x ^T

Q= energy (heat) required

s =specific heat capacity

m = mass 1.6-g

^T = change in temp 18 C

thus, specific heat capacity is the Energy used, divided / by the mass of the sample, times X by the temp change.

1.6 x 18 / 5.8 = 0.2013889 rounded to 0.20

Golds specific heat capacity is super fast 0.13 the sample at 0.20 is not pure gold.

While the above is true. And, quite a simple and accurate measure of a substances purity. Not many people have access to the analytical equipment needed to measure an elements calorific value at home. but, its also something ive never seen mentioned in any mining reports or prospecting methods before so worth exploring more. measuring the rate of temp change. can also work in reverse.

The reason i think this is of value is because we can today use low Earth orbit satellite thermal imaging to detect temperature anomalies on Earth surface from space. There would also have to be software that flattens contours or isolates them to lessen the effect of temp altitude gradients. It would work i think on any massive surface deposits. Iron, Silica, Sphalerite, Galena, Corundum, Cassiterite, etc. And, because of gold incredibly low heat capacity. compared to the iron rich host rock It may even pick up decomposed gold veins on the surface, because the rock surrounding the vein is at least 8 times slower to cool. WA as an example.

The planet Mars in 2010 had its mineralogy mapped with a thermal imaging equipped satellite called THEMIS. NASA

Statistics: Posted by Philski — Sat Jun 07, 2014 2:00 pm

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And, things do go wrong. Here in Tasmania we had 2 leach pads rupture at different sites and spew toxic cyanide into our environment. And we still use them, They are safer today apparently.

The second pad ruptured behind Beaconfield in the early 1990's.

The system is still there today and has not had a leak since? the Lea river alluvials for Torque Mining go in this leach pad. http://epa.tas.gov.au/documents/proto_resources_noi.pdf

Henty Gold mine and many others exist in Tas.

There are also dangers of ground water contamination.

Another on the very near horizon is deep sea in situ leach mining. They will eventually drill the ocean floor, frack the rock then pump acid down into the rock, dissolve the minerals, then flush it all out with sea water to make the solute come out and then plug it. So it has eco dolphin appeal.

acid drainage link:

http://www.mrt.tas.gov.au/pls/portal/do ... REPORT.PDF

Statistics: Posted by Philski — Thu Feb 20, 2014 11:14 pm

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Acceleration due to gravity g = 9.80665 m/s2

Avagadro's number NA = 6.022137 x 1023

Faraday Constant = F = 96,484 C mol-1 = 96,500

Masses of Subatomic Particles: electron me = 9.10939897 x 10-31 kg = 5.4857991 x 10-4 u

proton mp = 1.6726231 x 10-27 kg = 1.0072765 u

neutron mn = 1.6749286 x 10-27 kg = 1.0086649 u

Speed of Light c = 2.997925 x 108m/s

Proton Charge e = 1.60219 x 10-19 C

Atomic Mass Unit (amu or u) 1 u = 1.660540 x 10-27 kg

Foot (ft) 1 ft = 12 in = 0.3048 m

Pound (lb) 1 lb = 16 oz = 0.45359237 kg

gravitational potential energy U = m g h

kinetic energy K.E. = (1/2) m v2

circumference of a circle/sphere circ = 2 π r

cross-sectional area of a circle/sphere A = π r2

volume of a sphere V = (4/3) π r3

force on a charged particle in an electric field F = q E

mass defect E = ∆m c2

Statistics: Posted by Philski — Sat Feb 15, 2014 1:16 pm

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Classification is the condition that favors separation by size and not density.

Classification is also method of separating minerals into two or more products based on there different velocities under the effects of gravity in a viscous medium that offers some resistance. Air, water or any other fluid that offers resistance can be equated. under vacuum and under constant acceleration it has an infinite rate of acceleration.

For instance In a vertical tube with a constant stream of resistance moving upwards the lighter particles will float upwards and the heavier will drop or remain stationary in the fluid/air. Could be a new sluice design right here.

Larger particles >5mm do create turbulence and are calculated differently because of the turbulent flow they create.

Stokes law which takes into consideration the viscosity of the fluid, speed of gravity, particle size and density of the fluid is used to calculate the smooth flow of small particles and the laminar flow the generally produce.

in a working plant this is used on particles that could not be efficiently screened and the hydrocyclone that operates under centrifugal force and is typically used today. hydraulic that operates under gravity. similar to a sluice box

The hydro uses mixed ore with water (Generally 40%) and the lighter fraction is shot up and out while the heavier minerals hit the wall and directed down towards the bottom. The biggest advantage with the hydrocyclone is the centrifugal forces are much higher than gravity alone forcing the particles to settle out at a faster rate.

Concentration of minerals is by means of one or more of the minerals characteristics. For gold its specific gravity. Mineral concentration by gravity, flotation, electrostatic, and magnetism.

The 3 factors that describe the extent of concentration are Recovery, Grade and Ratio of concentration.

Recovery is mass of valuable in product stream divided by mass of valuable in input stream x 100

Grade is mass of valuable in stream divided by mass of valuable in stream AND waste in stream x 100

Ratio of concentration mass of feed stream divided by mass of concentrate.

for example a flotation test on Galena Pb (lead)

Head 1500 kg @ 8.55%Pb

cons 220 kg @ 57% Pb

Tailings 0.2% Pb

Ratio of Concentration 1500 / 220 = 6.82

The recovery is a trade off between grinding the nano size for a high con % or hand picking pure ore from the heap at a loss of recovery rate. You can not end up with more than 100% of what is in the feed, Nothing can be created or destroyed. Any loss will be in the tailings. This is all material balancing. And a science type may call it the conservation of matter. Product in = product out.

Gravity Separation This is one we all know. A pan, sluice box etc. Others include spirals, shaker table and an extreme one is the use of Mercury (Hg) to "float away" the light material because of its high SG and allow the gold to settle out while the the light rock floats away. Similar to oil floating on water, because oil is the lighter.

Image taken from: creative commons

I will add more info and calculations (arnt they fun) as time permits.

Statistics: Posted by Philski — Thu Feb 13, 2014 6:39 pm

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Ore Dressing or Comminution is the process of sizing, crushing, milling and grinding ROM ore (Run of Mine Ore) to the desired size required to extract the valuable minerals. Generally the size of flour. The process also consumes vast amount of energy and there is a limit to how small it can be ground before the cost to produce it outweighs the return.

The Primary Crusher is typically the first stage of crushing after blasting and sizing. The majority of ore minerals are disseminated throughout the gaunge (non valuable waste rock) and need to be small enough to break it free of the surrounding rock. The waste rock goes out as tailings.

It is impossible to recover 100% of the valuable ore. But the Comminution process is in the high percentile of capture.

The benefits of Comminution is its saving on Freight costs. Reduced losses of valuable minerals and reduction on the cost of hydro-metallurgy processing later on.

Typical as blasted ore is 10 cm - 1 meter in size and the required end size 0.1mm (tenth of a mm) or lower.

Stage 1 After sizing though a grizzle, trommel or screen. Primary Crushing is by way of a jaw crusher or gyratory Crusher. The later has a higher throughput of ore Size reduction 10cm -1cm

Stage 2 is through a cone or roll crusher. Size 1cm - 1mm

Stage 3 is via ball or rod mill 1mm - 0.1mm

There are also autogenous mills that use the rock itself to impact on itself and reduces balls and rod. But at the cost of lining replacement. These mills have a much larger radius to assist the impact of the falling rock on itself.

It has been found that reducing the ore size in stages is more economical from a power input level that trying to do it all in one go.

Some of the math a metallurgist will work out are size reduction ratios, energy needs, Critical mill speed and valuable mineral processing losses.

Mill speed is to stop the mill centrifuging. 70% is a good level to aim for and most mills operate between 50% and 80% of Critical Speed and can be worked out using the formula Nc = 42.3 / D 1/2

where Nc is the critical speed of the mill in Revolutions per Min and D is the diameter of the mill in meters. This is very basic and other formula incorporate ball diameter and mill diameter.

Reduction Ratio of Screen is E = % of total feed divided by % of what passes the screen. This is normally set at 80% of what passes or P80

Work Input or mill efficiency / comminution theory normally uses the Bonds work index and has limitation to ore size. While mathematically it works for smaller sized ore it has limits in larger size ore. Rittinger in 1850 postulated the crushing efficiency should be related to the surface area and the rocks particle size is normally worked out at 1.75 the area of a cube and in theory it works but in practice it needs between 100 and 1000 times more energy to crush.

Bonds work index is E= 10 Wi (one div the square root of the product minus 1 div the square root of the feed)

It should also be noted the the bonds work equation is worked out in Microns. so 2 mm is 2000 microns

Typical energy requirements

Coarse crushing 0.2 -0.5 kWh / Ton

Fine Crushing 0.5 - 2.0 kWh / Ton

Coarse Grinding 6 - 12 kWh / Ton

Fine Grinding 8 - 25 kWh / Ton

Statistics: Posted by Philski — Thu Feb 13, 2014 11:34 am

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If there is anything you would like to know equation wise. just ask. I can try and help. Im sure there are people here that work in the industry. that can be of more assistance with real life issues, My learning is theoretical.

Some places metallurgists work in Tassie. Temco, Bell bay. Rennison Bell, Hellier, Port latta and Hobart.

Statistics: Posted by admin — Fri Jan 10, 2014 11:07 pm

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