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zaqqaz22

Parts Per Million.(Ppm) Vs Grams Per Ton.. Does It Stack Up?

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Hello All.

 

I am rather perplexed how the 1ppm = 1 gram per ton  rule/assumption works..

 

Maybe someone out there who is an expert in the field of geochemistry/metallurgy might be able to help.

 

I would have assumed that 1ppm literally meant 1 atomic or molecular PART per 1 million other atomic or molecular parts..

 

In consideration I would also have assumed the various atomic weights/masses of various elements would have a major impact on this assumption.

 

Ie.. Given gold has a specific gravity of approx. 19.3.. and then if we can assume that the host material (silicates, carbonates, oxides etc) have an average combined SG of say 2.8. Then the sum I would have presumed would run like this; 

 

 1 ppm  =    

19.3 :  2.800,000       or    

1.00 : 145,077           or    

6.89 : 1,000,000        ie.                   6.89 grams per ton.. when it comes to gold..

 

I got thinking about this when looking at assay result for scandium..     With an SG of 3.0 for Scandium, I find it hard to believe that 1 ppm scandium and 1 ppm gold would both equal 1 gram per ton of contained commodity..  It just does not ad up.. or am I missing something fundamental..

 

Or does PPM  actually not mean PPM at all??

 

 

Any guidance or insights most appreciated !!!

 

cheers Tony

 

 

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I'm not sure what you are trying to represent with you math - that's not any way to calculate density. What you are trying to do doesn't make any sense to me.

Adding one gold atom to one million quartz atoms will make a change so small that you cannot actually measure it in terms of density.

It would be like adding a drop of water into a bucket full - you wont be able to measure the increase in weight from the extra drop on any normal weight scale. 

 

it could be done perhaps this way:

For a million parts quartz and one part gold

(1,000,000 x 2.7 - quartz) + (1 x 19.3 - gold) = 2,700,019.3

2,700,019.3 divided by 1,000,001 parts =  2.700017 grams/cc

so your 2.7 density sample with one part in a million of gold added is now 2.700017, a change so small that it virtually cannot be measured by any normal density measurement. Like I said, a drop in the bucket, a change so small you cannot measure it.

 

Calculating the gold part of a gold-quartz sample by density really requires that the gold be in the range of 10,000 ppm - the same as around 1% by weight. If it gets much less than that the density method is just too rough and inaccurate that any numbers you get just don't mean much.

 

You are correct that 1 ppm equals in an approximate, rough way 1 gram per ton or around 0.03 ounces per ton.

 

1 ppm is one ppm by weight, so one ppm of scandium or gold are both one gram in a ton, as one gram gold is the same weight as one gram of scandium.

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I'm not sure what you are trying to represent with you math - that's not any way to calculate density. What you are trying to do doesn't make any sense to me.

Adding one gold atom to one million quartz atoms will make a change so small that you cannot actually measure it in terms of density.

It would be like adding a drop of water into a bucket full - you wont be able to measure the increase in weight from the extra drop on any normal weight scale. 

 

it could be done perhaps this way:

For a million parts quartz and one part gold

(1,000,000 x 2.7 - quartz) + (1 x 19.3 - gold) = 2,700,019.3

2,700,019.3 divided by 1,000,001 parts =  2.700017 grams/cc

so your 2.7 density sample with one part in a million of gold added is now 2.700017, a change so small that it virtually cannot be measured by any normal density measurement. Like I said, a drop in the bucket, a change so small you cannot measure it.

 

Calculating the gold part of a gold-quartz sample by density really requires that the gold be in the range of 10,000 ppm - the same as around 1% by weight. If it gets much less than that the density method is just too rough and inaccurate that any numbers you get just don't mean much.

 

You are correct that 1 ppm equals in an approximate, rough way 1 gram per ton or around 0.03 ounces per ton.

 

1 ppm is one ppm by weight, so one ppm of scandium or gold are both one gram in a ton, as one gram gold is the same weight as one gram of scandium.

 

 

 

Jeepers!!!!  wish I was digging 10,000 ppm gold dirt??  that would be over 320 oz per ton.. !!!

 

 

Ok, so I think you have nailed it with your last line..
 
 "PARTS" in  PPM must not literally mean "PARTS" on a molecular or atomic level.. otherwise the Atomic mass of the elements would have a large impact on the conversion to grams per ton..  
 
This is what I was initially trying to fathom..
 
But I think you are right,  PPM represents a weight to weight ratio...   The boffins need to change the nomenclature, the term is misleading.
 
 
 
funny just found this on Wiki..    this is the exact problem...     the diff between a Mass Fraction and a mole fraction..
 
Seems even the ruling international body of weights and measures has issues with PPM as well
 
“a continued source of annoyance to unit purists has been the continued use of percent, ppm, ppb, and ppt.”
 
 
Mass fraction vs. mole fraction vs. volume fraction[edit]

Another problem of the parts-per notation is that it may refer to mass fractionmole fraction or volume fraction. Since it is usually not stated which quantity is used, it is better to write the unit as kg/kg, mol/mol or m3/m3 (even though they are all dimensionless).[8] The difference is quite significant when dealing with gases and it is very important to specify which quantity is being used. For example, the conversion factor between a mass fraction of 1 ppb and a mole fraction of 1 ppb is about 4.7 for the greenhouse gas CFC-11 in air. For volume fraction, the suffix "V" or "v" is sometimes appended to the parts-per notation (e.g., ppmV, ppbv, pptv).[9][10] Unfortunately, ppbv and pptv are also often used for mole fractions (which is identical to volume fraction only for ideal gases).

The usage is generally quite fixed inside most specific branches of science, leading some researchers to draw the conclusion that their own usage (mass/mass, mol/mol, volume/volume, or others) is the only correct one. This, in turn, leads them to not specify their usage in their publications, and others may therefore misinterpret their results. For example, electrochemists often use volume/volume, while chemical engineers may use mass/mass as well as volume/volume. Many academic papers of otherwise excellent level fail to specify their usage of the parts-per notation.

 
 
here in link..
 
 
 
 
 
 

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The key to the effect of mixing two things together, volume or mass, is a significant amount of both materials in the mixture - if its essentially all one or the other, the properties will be of the one that is the majority. 

If I add a tiny bit of tobacco smoke the size of a green pea into a house full of air, you will not smell any tobacco. If 10 smokers smoke 10 cigarettes each in a sealed house, you will smell the smoke.

If you put one tiny grain of salt from a salt shaker in a 5 gallon bucket of water, you wont be able to taste the tiny amount of salt. If I put 3 cups of salt into 5 gallons of water, you will be able to taste the salt.

If I mix 1 ppm (volume or weight) of gold into a million parts of quartz, you wont see any change in density of the mixture.

The fact is that one PPM is a very tiny, tiny amount. Hard to grasp its so tiny.

The method you were using to figure combined density is wrong and cant yield a correct answer, weight or volume.

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I think the general concept I am using is correct..

 

1 ppm is indeed a small amount no doubt, this is beyond question, but  if we assume an assay of 1 ppm or 2 ppm equates to 1 g/t or 2 g/t  then all of a sudden a 1 ppm variance can mean the difference between an economically viable gold deposit a uneconomic gold deposit..   

So in large scale mining these very small numbers can have huge consequences..

 

Though this is not  really my point..  

 

My point is;

 

if assays and chemical analysis are done as molecular analysis. (i.e. mole's), which I assume they are?..  

Then the results are a ratio of atoms/molecules etc..  

Considering these atoms/molecules have varying masses/densities, then correlating the results straight from Mole : Mole ratios to Mass: Mass ratios (i.e. grams per ton) will require a conversion factor based on the different densities of the particular substances involved..

This is given as an example in the Wiki article with gasses, in this case CFC-11, in which case to convert mole fractions to mass fractions the conversion factor is 4.7..

 

So to get back to my initial calculations, which seems to have confused everyone..  let me try re-represent them;

 

ie for gold  -     SG - 19.3   g/cc       -        Gangue rock (mix, silcates, sulphides, carbonates)  -  SG 2.8  g/cc          (approximation, for example..)

 

1 ppm   gold   molecular analysis (i.e. mole) 

 

1: 1,000,000

 

So for mass we would then need to apply the  SG's  for gold and host rock (Gangue)..

 

(1 x 19.3g/cc)  : (1,000,000 x 2.8g/cc)

19.3                 :  2,800,000

 

Ok so now to get it back to 1,000,000    or 1 ton if applying to grade.  we need to dived both sides by 2.8.

 

19.3/2.8           :  2,800,000 /2.8

 

6.89                 : 1,000,000

 

or  6.89 g/t..

 

 

 

Anyways, this is all rather academic..  And I suppose the ultimate question is to a practicing industrial chemist or a metallurgist..

 

When assaying/analysing for economic elements / minerals, is the analysis done as a molecular (mole:mole) analysis?  - in which case to convert to g/g would need a conversion factor for mass..

And in which case there is no way 1ppm gold and 1 ppm scandium can both work out at 1 gram per ton.. (my original Q !!).. 

 

Or is the analysis done stickily by mass:mass   ..  in which case the answer is simple and 1ppm of anything analysed    would equal 1g/t

 

 

It is well worth reading the wiki article on this..  seems the PPM notation causes confusion all over, especially between differing fields of science..    So i'm not the only one !!..    Seems PPM notation needs to be scrapped !!!

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Assays are done by weight.

Use google and type in "fire assay".

 

Quit trying to over think this.

This isn't an assay to determine if it is .995 fine or .9999 fine.

It is just a basic assay.

The deposit isn't homogeneous, continuous or exactly defined in size and shape.

The question is, "Is this deposit economic?"

 

This is chemistry at the level not much higher than, "Hey dude, look what happens if we mix vinegar and baking soda."

All of your over-thinking is based upon quantitative chemistry requiring technical or higher grade chemical reagents.

Gold in it's natural state does NOT, I say again does NOT, have a density of 19.3grams/cubic centimeter.

The gangue rock may or may not have an S.G of 2.8, but most metal sulfides have S.G. >5.0.

You are dealing with a bushel basket of unknowns.

Most are irrelevant.

 

"Seems PPM notation needs to be scrapped !!!"

No sir. You need to put away your junior Nobel prize in chemistry set and learn something about mining.

PPM is exactly what works best.

1PPM is 1 gram per tonne.

A tonne is 1000 kilograms

A cubic meter of ore carrying rock will weigh about 2.5-2.7 tonnes.

Ergo that 1PPM translates to 2.5-2.7 grams per cubic meter.

There are 31.1 grams per ounce troy (ozt).

Gold is sold by weight.

Most gold prices are quoted in USD/ozt.

 

Excavation of rock is measured by volume. You drive an adit in feet or meters.

Moving the ore bearing rock to the mill is by weight and volume.

Milling is rated in tons/tonnes per hour.

PPM makes abundant sense.

 

Quoting some drivel from wiki just infers that you place a good deal of confidence in unfounded opinions formed from people living in their parent's basement with no other claims to fame than the number of wiki edits they pulled off.

I think it was Marcus Aurelius who stated something like, "The opinions of 10,000 men means nothing if they don't know anything about the subject."

That is exactly what wiki is.

A classic example of the fallacy of the collective wisdom of 10,000 fools.

 

And once again, that quote:

"Seems PPM notation needs to be scrapped !!!"

Really? Speaking only for myself, I think you need to learn the basics before you start recommending changes to the process of assaying.

Have you ever needed an assay done?

 

If I seemed a bit brusque, just consider it as a natural response to:

"I think the general concept I am using is correct.."  No

"..., which I assume they are?."  Assume?

"..., as an example in the Wiki article with gasses, ..."  Already covered wiki

"Anyways, this is all rather academic.." Then why argue it?

"..., is the analysis done as a molecular (mole:mole) analysis?"  You don't know, but you already have an opinion?

 

And finally,

"It is well worth reading the wiki article on this.."

To which I say, male bovine excrement.

 

eric

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When assaying/analysing for economic elements / minerals, is the analysis done as a molecular (mole:mole) analysis?

No. Its done as an ounce (weight) per ton or gram (also weight) per ton.

 

in which case to convert to g/g would need a conversion factor for mass..

Since its done on a weight per weight basis, no conversion of something else to weight is needed.

 

there is no way 1ppm gold and 1 ppm scandium can both work out at 1 gram per ton..

Since virtually all metal analysis is weight per weight, then yep, a gram of gold is the same weight as a gram of scandium or a gram of silver or a gram of lead, etc. A gram is a gram.

 

a 1 ppm variance can mean the difference between an economically viable gold deposit

Actually analysis for gold are normally done in parts per billion, and one thousand ppb is the same as one ppm. An error of one ppm is really large and does not happen. Also, lots of samples are taken and the results are averaged, so the error of one sample is minimized. .

 

 

This is given as an example in the Wiki article with gasses

So if we are looking at the PPMv of CO2 in a stack exhaust, then yes gas analysis might be done in volume, but we were talking about metals, not gasses, and not all analysis of all substances can be assumed to be exactly the same.

Metal analysis are done as a weight per weight because prices paid for metals are weight based. No one buys a cc of gold, you buy an ounce or you buy grams. Manufacturers don't purchase a liter of copper, they buy pounds or tons of copper. The difference is important.

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Nice one eric N.  Your undoubtedly a real champion.. !!!

 

 

Despite you opinion that Wikipedia is 100% drivel (as you would obviously know), it is stated in the Wiki article even the "Real Authorities" at the BIPM have major issues with the PPM notation for the exact same reasons I have..   Feel free to write them an email and tell them how stupid and overly academic they are being too, in-between mining your next million ounces that is, you rocket scientist you!!

 

Anyways. I did finally get in touch with a "real" practicing industrial chemist, who was kind enough to Politely inform me that indeed, in the modern world when doing "metallurgical style" chemical analysis the results are first analysed as mg/kg (just like in the good old days)..  but now days these are transposed into PPM, something that he even admitted was not ideal and can cause confusion between the various fields of science..

 

Hope I am not "overthinking" and getting too academic for you again eric?? 

 

BTW,  gold in ore deposits is does not have an SG of 19.3???  for a self proclaimed genius you a right off track there, or should I have used 19.32 at 20 degrees Celsius maybe?? ..  Before you get your knickers in a twist again, my analysis is for gold, not native alloys, fineness does not come into it..

 

Since you are such a genius eric, you really need get on Wiki and rewrite everything there is to know about gold, assaying, chemistry.. etc etc. us poor regular folk are obviously being intentionally deceived and misinformed by those evil pimply faced basement trolls..

 

You obvious have some degree of knowledge. shame you have no manners, no humility and no tact whatsoever..

 

In fact you seem to be propagating the exact same "troll like" online persona as those pimply faced social misfits lurking in their mothers basement, that you infer are polluting Wikipedia with all that so called irrelevant mindless garbage..

 

Just to rub it in,  I will say it again "PPM notation needs to scrapped." . it is a unit-less ratio and can been misinterpreted. there, boohoo over that..!! 

As far as gold/ commodity analysis goes mg/kg or g/t  is much more pertinent. !!

 

Now finally, just to let you know I might be a bit rusty having not worked in the Mining Industry for 20 odd years, but I am actually a Geologist by University education. (Major Geology, Sub Major Physics..)...  And yes, during my time working both in mines in Australia and on numerous exploration projects world-wide, I oversaw literally thousands and thousands of samples and assays, primarily for gold..  ALL done in grams per ton... NOT PPM. !!!!

 

 

I might indeed  have been over-thinking on this subject.. Guilty as charged..

 

But you??  brusque ??  quite a word, but it does not really do you justice eric, regardless, thanks for the education...  Troll 101..

 

Since you are such a genius btw eric,  here's another one for you, when I am getting analysis back from a Niton gun (XRF), for % of Scandium but intend on extracting the metal as an oxide, then what conversion should I make to compensate for this?? do tell..

 

Seems I can throw away all my chemistry books and banish Wikipedia, I have eric the oracle..  

 

Now you can get back on your soap box and pontificate some more eric !!!

King Kong and his Keyboard..

 

All yours buddy..

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Thanks Chris for you input..  

 

The article below defines the issues at play that I was querying and pretty much concurs with your input, and is based primarily on the difference in the definition of "Scientific" and "Industrial" measures of concentration.  

Although mainly dealing with solutions and air contaminants, there is also reference to metallurgical analysis.

 

 

Taken from United States Naval Academy Website..  Link below

            http://www.usna.edu/ChemDept/_files/documents/manual/apdxN.pdf 

 

More "male bovine excrement" eric??  Take it up with the US Navy !!!

 

                    

Appendix N


                    

CONCENTRATION UNITS

                    

Chemists and engineers often encounter technical situations that require the description of the relative
quantity of some substance in terms of its concentration in a solution or in air. For these purposes a variety of
concentration units have been developed that can be used according to the needs and requirements of the job.

               

Concentration units can be divided into two broad categories. There are those units that are used in
research and scientific applications and those units that are used in industrial applications. These categories are
not firm and fast, but they are useful in understanding when one unit is used in preference to another. Several
common
scientific and industrial units are listed below:

         

SCIENTIFIC              INDUSTRIAL

 

molarity (M)                mass percent (%)
molality (m)                 parts per million (ppm)
mole fraction (X)         parts per billion (ppb)

                

The primary difference between scientific and industrial units is that in scientific units the identities of the
solvents and solutes are known and are usually pure substances; in industrial units, the solutes and solvents may be
mixtures of materials whose composition is not well defined. The use of scientific units requires the calculation of
a number of moles, therefore the molar mass must be defined. However, this requirement is not present with the
industrial units.

                    

A. SCIENTIFIC UNITS
1. Molarity (
M)


                    

Molarity is defined as:

                    

M =  (mol solute)/(L solution)

                    

and is reported in units of mol/L or molar. Molar concentrations are the most common of the scientific
concentration units because molar solutions are easy to prepare. In general, a molar solution is prepared by placing
a known quantity of solute in a volumetric flask and adding solvent until the flask is filled to the calibration mark.

                 

Molar concentration is used in many common laboratory applications and is the concentration unit most
frequently encountered in the general chemistry laboratory. One limitation in the use of molar concentrations is
that the volume of the solution changes with temperature. This results in a change in the molar concentration. For
work at constant temperature, however, this limitation does not exist.

                    
                    

2. Molality (m)

Molality is defined as:

                

m = (mol solute)/(kg solvent)

                    

and is reported in units of mol/1000 g, mol/kg, or molal. Molal concentration is less convenient to use than
molarity because the mass of the solvent must be determined rather than its volume. In practice, generally only
small quantities of these solutions are prepared and therefore this inconvenience is minor.

                  

Molal concentrations are used in experiments determining freezing point depressions, boiling point
elevations, and in other cases where the temperature of the solution changes over the course of the experiment.
Molal concentrations eliminate the problem of the dependence of volume on temperature seen with molar solutions
because masses are not temperature dependent.


                    

3. Mole Fraction (X)

Mole fraction is defined as:


                    

X = (mol solute)/(mol solute + mol solvent)


                    

As with molality, preparing solutions using mole fraction units requires the weighing of solute and solvent
so that the number of moles can be calculated. For many solutions, the quantity of solute is small compared to that
of solvent, so the numerical values of mole fraction are frequently very small numbers. Because moles are the units
of both numerator and denominator, mole fraction is a unit-less quantity.


                    

B. Industrial Units

1. Mass Percent (%) (or percent mass)


                    

Mass % is defined as:


                    

A similar relationship holds for volume percent (or percent by volume).

               

% =  (mass of solute) /(total mass of solutionx100

                                                          

                    

% = (volume of solute)/(total volume of solution) x 100

volume

                    

Mass percent is used to express the concentration of substances that are not pure, for example, the content
of butterfat in milk. Butterfat is not a pure substance, but its mass percent in milk determines the legal difference
between skim milk, whole milk, and table cream.


                    

Mass percent is also used in the metallurgical industry to describe the quantities of different components
in alloys. Certain generic names such as "stainless steel" imply the presence of certain minimum levels of different
components in the steel. In this case, the definitions are not legal ones, but are standard compositions accepted by
    

industry.

 

Examples are:

COMMON NAME                
MASS-PERCENT ELEMENTAL COMPOSITION


                    

brass                                        67-90% Cu, 10-33% Zn
dental amalgam                       50% Hg, 35% Ag, 15% Sn
18-carat gold                           75% Au, 10-20% Ag, 5-15% Cu
stainless steel                          73-79% Fe, 14-18% Cr, 7-9% Ni


                    

2. Parts per Million

 

Parts per million (ppm) is defined as:
                                     

ppm =  (mass of solute) / (total mass of solution)     × 106

                 

The unit “parts per million” is usually used for very dilute aqueous solutions. For very dilute aqueous solutions the
density of the solution is assumed to be the same as the density of pure water (1.00 g/mL), so that one liter of
solution has a mass of 1000 g and 1000 L of solution has a mass of 10
6 g. This information gives two additional
definitions of parts per million.

             

ppm = (g solute)/(1000 L solution)


                    

ppm = (mg solute)/(L solution)


                    

Parts per million is used to describe concentrations in solutions containing poorly defined or unidentified
solutes or mixtures of solutes. Parts per million is also used to describe concentration levels to those who are
unfamiliar with the concept of moles.


                    

Tap water contains a variety of dissolved impurities, mostly minerals. A simple way of describing the
levels of these impurities, often called dissolved solids, is to measure out a sample, 10 mL for example, into a
weighed aluminum cup and evaporate the water. The mass of the remaining solids is determined by difference.
Dividing the mass in mg of remaining solids by 0.010 L gives the concentration of the dissolved solids in ppm.
Notice that the identity of the solids is not specified, but a measure of their concentration is known.


                    

The Navy uses the level of chloride ions in boiler water as an early warning indicator for seawater leaks
into condensers. The titration test that is used precipitates the chloride ions as a mercury compound. The chloride
ions themselves are present in water along with many cations including sodium, potassium, magnesium, and
calcium ions. Because it is not appropriate to talk about the amount of sodium chloride in the boiler water, the
results from the mercury titration are used to determine the mass in mg of chloride ions in the sample and are in
turn expressed as ppm of chloride.

                    
 
                    

3. Parts per Billion


                    

Parts per billions is defined as:

ppb =  (mass of solute)/(total mass of solution) × 109

                    

For very dilute aqueous solutions the approximation is:

              

ppb = (μsolute)/(L solution)

 

                    

Parts per billion is used for reporting trace contaminants of substances in water supplies and for
substances present in extremely small quantities in other systems.


           
            

        

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