Sodium Tungstate Dihydrate for Anticorrosion of Electroplated Coating

NAME: SODIUM TUNGSTATE 

CAS:10213-10-2
M.W.:329.86
M.F:Na2WO4.2H2O
Appearance: colorless crystal or white crystalline powder;
application:It is used in the manufacture of tungstic acid and tungstic acid.
Hazard Description: avoid contact with skin and eyes. Keep the container closed. Avoid ingestion and inhalation.



SODIUM TUNGSTATE  
Purity as Na2WO4.2H2O: 99% min.,
Purity as WO3 : 69% min.,
Chloride: 0.04% max.
Pb: 0.002% max.
Fe: 0.002% max.
Insoluble in water: 0.01% max.
PH value: 7~9



Content determination:
Determination of tungsten trioxide (WO3) content in sodium tungstate (cinchonine gravimetric method)
1.Method summary: tungstic acid was precipitated with cinchonine hydrochloride in a hot solution with pH value of 3.00-4.4, and then separated from impurities. After being burned, it was tungsten trioxide, weighed and colorimetric.
2. Reagents: methyl violet indicator 0.1%, hydrochloric acid (1 + 1), cinchonine hydrochloride solution 10% (prepared with 1 + 1 hydrochloric acid), cinchonine hydrochloride lotion 0.2%, solid NaOH, broad test paper.
3. Operation steps: weigh 0.5g of sample into a 250ml beaker, dissolve it with a little water, add 100ml hot water at 60 ~ 80 ºC, neutralize 2 drops of 0.1% methyl orange finger agent (if the indicator is brown), neutralize it to red with hydrochloric acid (1 + 1), add 10ml of 10% cinchonine under continuous stirring, continue stirring to make the precipitation coagulate rapidly, and then stand still when the upper liquid is clear. After the precipitation sinks, filter the filtrate with rapid quantitative filter paper The precipitate is washed with 0.2% cinchonine lotion for more than five times in a 250ml volumetric flask. After washing, the precipitate is transferred into a porcelain crucible together with filter paper, dried and carbonized on an electric furnace, then carbonized in a muffle furnace at 750-800 ºC for 30-45 minutes, cooled and weighed. The filtrate was determined by tannin and methyl violet colorimetry.
4. Calculation of analysis results: WO3 (%) = (w / g) × 100 + C. Where: W is the weight of tungsten trioxide (g), G is the weight of weighed sample (g), and C is the content of WO3 measured in filtrate.
5. Precautions:
1,The precipitate must be cleaned of sodium ion, otherwise the burned product will be black and the result will be high.
2, The indicator can be 0.1% methyl orange, and then the filtrate can be determined by thiocyanate colorimetry.
The method is as follows: pour the filtrate from the volumetric flask back to the beaker containing the original sample, add solid NaOH into the beaker until the pH of the filtrate is more than 12, and then return the filtrate to a 250ml volumetric flask, dilute to the scale, and dry filter. The following is carried out according to thiocyanate spectrophotometry.