Rapid chelatometric determination of tin and copper in phosphor bronze

1. The determination of tin: The acid concentration of the solution obtained by decomposition of a sample in nitric and hydrochloric acids is brought to 0.10.3N. The temperature is adjusted to 3050°C, and M/100 EDTA solution and thiourea are added to form tin chelate. The solution is cooled below 15°C, adjusted to pH 5±0.2 and back-titrated with M/100 zinc chloride solution using Xylenol Orange as an indicator. 2. Determination of copper: Sample solutions with and without thiourea masking copper are respectively titrated in the same way as in 1 and the amount of copper is sought from the difference in the titers of EDTA. Extensive examinations on the condition of chelate formation, effect of coexisting elements and the comparison with other methods indicate that the proposed method, can be applied for rapid determination of tin and copper in phosphor bronze. The presence of phosphorus has no influence. The analytical errors are 1% for 10 mg tin and 0.1% for 50 mg copper and the time required for an analysis is 18 min. For determination of tin in samples containing iron, lead or zinc, the former should be preliminarily separated as metastannic acid or by the methylisobutylketone extraction.