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Do not wash the SPT as it will dissolve.
Work only in a dust free environment.
Use only glass, plastics or 100% stainless steel equipment.
Use only warm distilled or demineralized / deionized water.
Note that tap water may contain calcium ions. Laboratory centrifuges should be used for rapid separations in the higher density range. Always add sodium polytungstate in portions to water, not vice versa, in order to expedite formation of solution.
Wash all material before using with SPT: The materials should be washed with warm distilled or demineralized / deionized water.
Avoid reducing agents : Do not allow the solution to come into contact with reducing agents. Reducing agents which will cause an irreversible blue or yellowish discoloration. An oxidation agent like hydrogen peroxide H2O2 can convert it to the original color. (See problem solving sheet, reducing agent sheet).
Avoid organic materials: The samples to be separated should be free of all organic materials which can cause a brownish discoloration. The samples should be free of soluble calcium ions. Calcium ions will react with SPT to form insoluble calcium metatungstate. Note: coal may contain calcium ions. (See problem solving sheet!)
Avoid evaporation of solution to dryness. It can form a concrete like solid which can not be removed mechanically from glass containers.
Overcoming viscosity problems: To achieve a rapid and quantitative separation you can centrifuge the mixture instead of the sink float procedure, thus easily overcoming viscosity problems.
Recovery of sodium polytungstate: The polytungstate solution can be recovered by washing respective particles with distilled or demineralized / deionized water. Rinse samples repeatedly. To filter off the solids from the liquid you should use a funnel with filtration paper.
Filter: Use Millipore 0.45 micrometer filters. Coffee filter can be used. By filtering (Millipore 0.45 micrometer filters) several times, you can get rid of both impurities and remaining crystals.
To evaporate the SPT solution: Minerals and all solids should be removed before evaporation. You can dry the SPT in an oven at a temperature of 248ºF (120°C). Lowest about 212ºF (100°C) and highest at 284ºF (140°C) depending on the concentration. Note that if the temperature is to high the solution can splatter, when to low it takes more time to evaporate to dryness.
Never evaporate SPT solution to a solid. The solid is very difficult to redissolve.
To decrease / increase the density: Dilute the solution with distilled water or add solid to increase the density as desired. You may evaporate the solution.
To re-purify the SPT solution: Our suggestion is to use a suitable extraction agent for the impurities.
To avoid the yellow color after recycling the SPT solution: Make it to your habit of washing the resin thoroughly several times and letting it sit in saturated NaCL to reconstitute the Na-resin, then rinse the salt with one bed volume of water.
To Avoid crystallization: Retarded crystallization from over-saturated solution is a common phenomenon for this type of compound. You can re-dissolve the crystals. However note that this recovered solution may be unstable and starts crystallizing very rapidly. The crystallization can take place within a few days to a couple of weeks.
By heating the solution and slowly evaporating you can obtain a clear high density solution.
Remedy: Use freshly made up solution and recover compound by evaporation from solution.
Don’t evaporate to dryness .... Never evaporate SPT solution to a solid. The solid is very difficult to redissolve. One strange aspects of the Sodium Polytungstate compound is that it dissolves as powder very rapidly when added in batches, it takes very long to redissolve once precipitated. To redissolve the concrete like precipitation add distilled water to the solid and exercise patience, it will take quite some time!
DO NOT store in glass vials (see storage of SPT).
Store the solution only in plastic or stainless steel containers.
DO NOT store in glass vials:
If you store the solution in glass vials be aware that the solutions are very aggressive and solve calcium ions from the glass. The resulting compound is insoluble.
You can re-dissolve the crystals and by filtering (Millipore 0.45 micrometer filters) several times, you can get rid of both impurities and remaining crystals. By heating the solution and slowly evaporating you can obtain a clear high density solution.
However please note that this recovered solution may be untable and starts crystallizing very rapidly. The crystallization can take place within a few days to a couple of weeks. Retarded crystallization from over-saturated solution is a common phenomenon for this type of compound.
Remedy: Use freshly made up solution and recover compound by evaporation from solution.
The following chart shows how many grams of solid sodium polytungstate (SPT) powder and distilled water you will need to obtain a solution with a specific density. To make certain that you have the precise density of the solution you desire, perform a measurement with a hydrometer. If required add either solid powder or water.
Please note:
Only use distilled water! Work only in a dust free environment. Use only glass, plastics or 100% stainless steel equipment. Add solid SPT to the water, do not add water to the solid SPT.
| Solution | DENSITY (g/ml) | SPT (Grams) | H20 (ml) |
|---|---|---|---|
|
1000 ml |
1,00 |
0
|
1000
|
|
1000 ml |
1,05 |
52 |
998
|
|
1000 ml |
1,10 |
121 |
979
|
|
1000 ml
|
1,15
|
195
|
955
|
|
1000 ml |
1,20 |
264 |
936
|
|
1000 ml |
1,25 |
325 |
925
|
|
1000 ml |
1,30 |
379 |
921
|
|
1000 ml |
1,35 |
432 |
918
|
|
1000 ml |
1,40 |
504 |
896
|
|
1000 ml |
1,45 |
558 |
892
|
|
1000 ml |
1,50 |
615 |
885
|
|
1000 ml |
1,55 |
694 |
859
|
|
1000 ml |
1,60 |
741 |
856
|
|
1000 ml |
1,65 |
808 |
842
|
|
1000 ml |
1,70 |
867 |
833
|
|
1000 ml |
1,75 |
927 |
823
|
|
1000 ml |
1,80 |
990 |
810
|
|
1000 ml
|
1,85
|
1051
|
799
|
|
1000 ml
|
1,90
|
1125
|
775
|
|
1000 ml
|
1,95
|
1178
|
772
|
|
1000 ml
|
2,00
|
1250
|
750
|
|
1000 ml |
2.25 |
1576
|
676
|
|
1000 ml |
2,30 |
1662 |
637
|
|
1000 ml |
2,35 |
1741 |
612
|
|
1000 ml |
2,40 |
1803 |
595
|
|
1000 ml |
2,45 |
1870 |
581
|
|
1000 ml |
2,50 |
1930 |
570
|
|
1000 ml |
2,55 |
1995 |
556
|
|
1000 ml |
2,60 |
2052 |
545
|
|
1000 ml |
2,65 |
2114 |
538
|
|
1000 ml |
2,70 |
2175 |
527
|
|
1000 ml |
2,75 |
2247 |
508
|
|
1000 ml |
2,80 |
2297 |
504
|
|
1000 ml |
2,85 |
2356 |
492
|
|
1000 ml |
2,90 |
2420 |
478
|
|
1000 ml |
2,95 |
2478 |
472
|
|
1000 ml |
3,00 |
2552 |
450
|
1 US Gallon = 3.79 Liter or 3790 ml
Sample calculation for a density of 2.94g/ml:
(Please see Mixing Chart for further density calculations.)
840 g SPT and 160g Water = 1000 g Solution (this is the weight of the solution)
The 1000 g Solution has a density of 2.94 g/ml.
The volume is 340 ml.
Please note that this is a mathematical calculation under ideal conditions.
To get one gallon of Sodium Polytungstate at a density of 2.94 g/ml you will need approximate 9.5 kg Sodium Polytungstate.
And this is the will calculation:
3790 ml : 340 ml = 11, 1471
11, 1471 X 840 g SPT = 9, 3635 kg SPT per Gallon volume
For five gallons SPT at a density of 2.94 g/ml you will need approximate 48 KG Sodium Polytungstate.
