Method for determination of lead in tin bronze

1.0000g of the sample was weighed and placed in a 250mL conical flask, 40mL(1+1)HCl and 5-10 mlH2O2 were added, dissolved at low temperature, boiled to remove hydrogen peroxide, and cooled by running water. Transfer to a 250mL volumetric flask, dilute with water to scale, shake well, the solution is the mother liquor. The amount of lead in tin bronze was determined as follows:

1. Reagent: thiourea - ascorbic acid: Add 1g ascorbic acid to 100mL thiourea (10%). New for use. Ammonium fluoride-potassium ferrocyanide: Dissolve 10g ammonium fluoride and 10g potassium ferrocyanide in a small amount of water and dilute to 100mL with water. New for use. 0.002m EDTA standard solution: Weigh 0.75g of EDTA disodium salt that has been dried at 80 ° C for more than 4 hours and dissolve in 400ml water, adjust pH= 5.0-5.5 with 20% NaOH solution (test paper), transfer to a 1000ml volumetric flask, dilute to scale, and shake well. The titration of lead by EDTA was obtained using standard samples by following the following analytical steps.

2. Analysis steps: absorb 10.00mL mother liquor, put it in a 250mL conical flask, add 30mL thiourea - ascorbic acid mixture, 10 mL ammonium fluoride - potassium ferrocyanide mixture, and shake well. Add 20 ml of Hexamethyltetramine solution (30%), two drops of bromocresol green alcohol solution (0.1%), and four drops of xylenol orange solution (0.5%). The endpoint was titrated with 0.002M EDTA standard solution until the solution changed from fuchsia to yellow-green.

3, calculate I a: :Pb%=T*V; T-edta standard solution to the percentage of lead titration (%/mL); V- volume of EDTA standard solution consumed during titration (mL); Note: Due to impurities in the tin bronze sample, the end point in the actual work is gray green.

The copper - based alloy with tin as the main alloying element is called tin bronze. The tin bronze used in the tin bronze industry has a tin content of 3% ~ 14%. Tin bronze with tin content less than 5% is suitable for cold processing. Tin bronze with tin content of 5% ~ 7% is suitable for hot working; Tin bronze with tin content greater than 10% is suitable for casting. Tin bronze is widely used in shipbuilding, chemical industry, machinery, instrument and other industries. It is mainly used to manufacture wear-resistant parts such as bearings and bushing, elastic elements such as springs, corrosion resistance and magnetic resistance parts.