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Substituição do nitrobenzeno pelo óleo de soja como uma proposta para o ensino do método de Volhard em Análise Quantitativa

Cristina Maria Barra, Bárbara Helena S Vieira, JOSÉ GERALDO ROCHA JUNIOR, Roberta Barra Pimentel Lã, Otavio Raymundo Lã
2017 Química Nova  
ANALYSIS. Volhard method is extensively employed in the teaching laboratories of classical quantitative analysis to chloride determination and is based on the reaction of Ag + with Cland Ag + residual titration with SCN -. Its drawback is that SCNreacts with the AgCl (s) initially formed. Nitrobenzene is used to avoid this stripping, but it is toxic to the environment and causes problems in final disposal. This work proposed the use of soybean oil as an alternative to nitrobenzene. The
more » ... nzene. The traditional and modified methods were applied in the standardization of 0.05 mol L -1 KSCN solution employing 0.05000 mol L -1 NaCl standard and the proposed modification did not affect the results obtained (α = 0.05). No significant differences were observed in the variances and NaCl recovery percentage in the titration of aliquots of 5.00 to 15.00 mL of solution of this salt. The recovery percentages obtained with soybean oil on the titration of synthetic 0.07000 mol L -1 NaCl samples diluted 1:1 to 1:100 were equivalent and even better than with nitrobenzene. The chloride determination in samples of saline, whey cheese, sea water and olive brine obtained by the modified method was satisfactory when compared to the official method with relative errors below 3%.
doi:10.21577/0100-4042.20170090 fatcat:tizblafftfc6rcvflz37ilhxgq