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This article describes the reaction between nitrite and safranine O. This sensitive reaction is based on the disappearance of color of the reddish-orange azo dye, allowing the determination of nitrite at the mg mL–1 level. A factorial optimization of parameters was carried out and the method was applied for the quantification of nitrite in sausages. The proposed experiment is attractive for the students, since several important aspects are addressed. First of all, it is not typical to explore color disappearance, especially when a chromophore such as the azoic compound safranine O is used. The quantification of nitrite is made in real samples (sausages), which are more relevant than synthetic samples. In addition, the presence of nitrite in foods leads to discussions on the function of nitrite in foodstuff and its effect on human health. The assembling of the FIA system is instructive for the students and can provide an ideal time to discuss concepts as fluid hydrodynamics, reaction kinetics, spectrophotometry, and mixing processes.

This work involved an evaluation of calcium hydroxide powder in the absence and presence of CO 2 . 0.12g of calcium hydroxide powder was used for each of 16 aliquots diluted in 100 mL of deionized water and distributed in 2 samples of 8 aliquots. ] in relation to the decrease in pH. However, the high alkaline pH of the calcium hydroxide powder was preserved in the absence of CO 2 , maintaining its reparative and antimicrobial properties.