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Author Topic: Colormetric Testing of soil and crushed rock  (Read 5046 times)

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Offline EMF

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Colormetric Testing of soil and crushed rock
« on: August 15, 2013, 01:28:58 PM »
I'm posting this on behalf of XT18000 Technical troubles   Pictures come later if they can be posted

 Colormetric Testing of soil and crushed rock
Here is step by step photos of how to test for Zinc, Copper, or Lead by using Dithizone dye, that can be
done on -80 mesh screened soil or crushed rock samples in the field if you want results very quickly;
on the spot, or in camp ( safer as far as results are concerned ); it is very hard to collect samples and
do testing at the same time without contaminating the dye or equipment that would result in failure.
It can be done if there is two people working as a team, one taking the samples and the other running
the tests, but it is far better to sample first and test later.
The test can be ran in just a few minutes if you have everything ready as you should to start with; I
strongly recommend running a number of these tests at home on samples that contain those elements
listed above so you learn how to run them without making simple mistakes and get used to the methods
involved. Let me first emphasize the need of keeping the containers of dye away from sunlight and to
keep it as cool as possible. Sunlight and/or heat will oxidize the dye in very short order ( a yellow -
green to brown ) color means it is oxidized and must be discarded and a new batch made up; wash
out any containers used with what ever solvent you decide to use, Xylene, Benzene, Toluene, or other
( but not mixed together ) be sure no oxidized areas are left, everything that this dye comes in contact
with must be spotlessly clean. These solvents are kind of high priced so to help hold down costs, use
gasoline, or charcoal lighter to wash things out with ,then rinse that out with small amounts of the
solvent used, your also throwing out a certain amount of the very expensive dithizone dye at the same
time. You must make every effort not to contaminate anything by being sloppy.
The size of each sample ( what ever amount used ) should be as exact each time, as any variations in it
will reflect in the results of the test, a sample with more in it will show as having more of a element in
it than one that has less in it. And as you will be working in ppm, you can see that this problem needs
to be guarded against as best as possible. You might use .5 gram of sample, or more, or
 in some cases.2grams,  try using a 1/10 gram, .25gram, and  .5 gram; if you don't get any results with
one size sample, try the next size, don't be tempted to use larger samples than these because these tests
are set up to operate in a narrow band, They work just fine like they are, if there is any of the three
elements in your sample, these amounts will show them just be sure you use the same amount from
sample to sample, be it volume, or grams.
The test tubes I use are 18x150mm but other sizes can be used as well, I have some that I bought in
a hobby store that are half as big and they work fine, just harder to find stoppers that fit them. Any
stoppers should not be made of cork, rubber is the very best and poly works as well. DO NOT USE
YOUR BARE HAND as a stopper as it will react with the dye.
You must be consistent as how you shake the test tube in the sample with dye step for much the same
reasons, to keep variations to a minimum for more consistent results. You have to learn how fast you
can shake a sample and count the shakes at the same time also, one step for 70 times, one step for 60
times, don't try to go to fast and thing will work out better, each down stroke works for me.
These are not hard things to do, read them over a couple of times to instill them in your brain and you
should have no problems.
You can make your test samples from most any old rock you have laying around by filing of a small
amount of those elements from tire wheel weights or a fishing sinker for the lead test, filings from any
galvanized metal for the zinc test, and any thing made from copper for that part. Read the other posts
on this subject I have posted and that will help. Read every thing you can about geochemical testing
and you will learn even more.
1.   items needed to preform the test; Xylene (or other solvents listed in text, Distilled water ( use only
      metal free water ), Wash bottle 250/500 cap. to  dispense dye and water, Strong dye and working
      strength dye, 25ml ( and 100ml  beaker not shown ) for mixing dye, Ammonium and dilute HCL
      to adjust pH, Sodium Chloride, ( test can be done without this while learning ), test tube marked with
      file scratch mark at 5ml with a fishing leader on a handle to be used as a centrifuge if muddy matter
      obscures the color of dye in last step, pH test strips, sample measure, sodium chloride measure,
      spatula to level off sample in measure, disposable type pipet 5ml with 1ml markings, 6" S.S. tweezers,
      small plastic funnel, small glass funnel,50ml Erlenmeyer flask or other to hold test tube while adding
      dye or adjusting pH, or adding sample.
 2.  Add sample
 3.  Add sodium chloride buffer
 4.  Add distilled water to 5ml mark and stopper tube
 5.  Shake up and down 70 strokes
 6. & 7.  check pH; adjust as needed to 5.0 to 6.5
 8.  Add 1ml of working strength dye and stopper tube
 9.  shake as before for 60 times
 10. check the color of the dye layer; if blue or green, there is no metal in the sample, wash the test tube
       and run next sample. If the dye layer is Pink there is Lead in it, if the color is Violet/Red there is Zinc,
       if Olive Green or Brown there is Copper,  Yellowish color bad, mix a fresh batch, or metal in the water,
       throw out and use different water ( deionized ), AKA metal free.
       Now you will want to know how much metal is in your sample ( if  any ) so you now add 1ml more dye
       and swish it around a little so it will mix with what's all ready in there, repeat this until the color turns
       back to green. This is called the end point and what you have done is called " titrating"
       multiply the amount of dye by 15 and that will give you the ppm in it. The reason is
       the first dye you added removed 7% or 15ppm, If it took 10ml. to reach the end point, you'd have 150
       ppm in that sample. If it takes more than 10ml.....  just record it as >150 ; the > means "more than".
       There will be other posts to explain some of the steps in more detail but for now this will work for you
       if you are interested in this process. Getting this far with the posting of it has been a labor of love and
       with out the help of EMF it would not have gotten this far.
       Questions or comments are welcome, that's how we learn

Offline EMF

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Re: Colormetric Testing of soil and crushed rock
« Reply #1 on: August 15, 2013, 08:24:22 PM »
So far, it looks as though XT's camera might have an incompatibility with the system here. This site doesn't accept pictures that his camera made, whether he tries or he sends them to me to post. Strange evil code somewhere.