NITRIMETRY TITRATION One method included in redox titration is diazotation (nitritometry). Diazotization titration is based on the formation of diazonium salts from free aromatic amine groups which are reacted with nitric acid, where nitric acid is obtained by reacting sodium nitrite with an acid. Diazotization is a reaction between primary aromatic amines/primary phenyl amines (aromatics) with nitric acid derived from sodium nitrite in an acidic environment to form diazonium salts. Diazotization titration can be used to: 1. Determination of levels of compounds that have free primary aromatic amines such as sulfanilamide 2. Determination of levels of compounds that have aromatic amines bound to other groups such as succinyl sulfatiazole, ptalyl sulfatiazole and paracetamol. In nitrimetry, the BE of a compound is equal to its BM because 1 mole of the compound reacts with 1 mole of nitric acid to produce 1 mole of diazonium salt. For this reason, for nitrimetry, the concentration of the standard solution is often expressed as M (molarity) because the molarity is the same as the normality. This nitrimetric method is based on the reaction between primary aromatic amines and sodium nitrite in an acidic environment to form diazonium salts (known as the diazotation reaction). NaNO2+ HC→ HNO2+ NaCl Ar-NH2+ HONO + HCl → Ar-N2Cl + H2O Nitrimetry is determining the concentration of a substance by titration using sodium nitrite solution as a titrant. This titration is used to determine the levels of Aromatic Primary Amine based on the reaction of the formation of diazonium salts with nitric acid at temperatures below 150C. Diazotation titration is based on the formation of diazonium salts from free aromatic amine groups which are reacted with nitric acid, where nitric acid is obtained by reacting sodium nitrite with an acid. This reaction is unstable at room temperature, because the diazonium salt formed easily degrades to form phenol compounds and nitrogen gas. So the reaction is carried out at temperatures below 15oC. The diazonation reaction can be accelerated by adding potassium bromide. The reaction occurs very quickly, so the titration must be carried out slowly. To maintain temperature conditions, ice cubes or a circulator can be used. Above temperature 150The C diazonium salt formed will be hydrolyzed to phenol and the reaction will not take place quantitatively. In the diazotation titration, determining the end point of the titration can use external indicators, internal indicators and potentiometrically. a. Outer Indicator The external indicator used is starch-iodide paste or you can also use starchiodide paper, when the solution is etched onto the paste/paper, the presence of an excess of nitric acid will oxidize the iodide to iodine and in the presence of starch/starch it will produce a blue color immediately. The starch-iodide indicator is sensitive to an excess of 0.05-0.10 ml of sodium nitrite in 200 ml of solution. The end point of the titration is reached when an instant blue color occurs when the solution is applied to starch paste/iodide starch paper. And if the solution is left for 1 minute, and the solution is applied to starch paste/starch iodide paper it will show the same results. To ensure whether the end point of the titration has really occurred, the test as above is carried out again after two minutes. The advantage of this indicator is that there is a clear color change, while the disadvantages are: a. Implementation is not practical because we have to etch every time we add titrant. b. The titrated solution must be cooled. a. Requires an orientation reaction to estimate the end point of the titration b. Outer Indicator End point determination can also be demonstrated with a mixture of tropeolinoo and methylene blue as internal indicators. The inner indicator consists of a mixture of tropeolin OO and methylene blue. Tropeolin OO is an acid-base indicator which is red in acidic conditions and yellow when oxidized by excess nitric acid, while methylene blue is a color contrast so that at the end point of the titration there will be a change from purple to blue to green depending on the compound being titrated. The use of these two indicators (external indicators and internal indicators) has disadvantages. For external indicators, estimates must first be known the number of titrants needed, because if you don't know the estimated amount of titra needed, then often test whether the end point of the titration has been reached or not. Besides that, if you carry out tests frequently, it is feared that a lot of the titrated solution (sample) will be lost during end point testing. Meanwhile, when using internal indicators, although the implementation is easy, often to overcome this, the potentiometric end point observation method is used. c. Potentiometric Method A good method for determining the nitrimetric end point is the potentiometric method using a platinum columnar electrode dipped in titrate. At the end point of the titration (the presence of excess nitric acid), depolarization of the electrode will occur so that there will be a very sharp change in current of around +0.80 Volts to +0.90 Volts. This method is very suitable for samples in the form of colored syrup.