BRS Pathology 5th pdf

Nephelometry and Turbidimetry

Free pharmacy material Nephelometry and Turbidimetry INTRODUCTION This is mainly used to determine the scattering of the light by the suspended particles present in the sample solution. The instruments used for the measurement of the scattering are called nephelometer and turbidimeters. The choice between the nephelometry and turbidimetry depends upon the fraction of light scattered. This light scattering by the particles which are present in the colloids is known as the Tyndall affect. Nephelometry is the measurement of the scattered light by the suspended particles at right angles to the incident beam. This method is mainly used for the determination of the low concentration suspensions. Turbidimetry is the measurement of the transmitted light by the suspended particles to the incident beam. This is used for the determination of the high concentration suspensions. PRINCIPLE Light scattering is the physical character of the sample which will depend on the following:

Diazotization Titrations

Free pharmacy material Diazotization Titrations INTRODUCTION The diazotization titration is nothing but the conversion of the primary aromatic amine to a diazonium compound. This process was first discovered in 1853 and was applied to the synthetic dye industry. The reaction mechanism was first proposed by Peter Griessin. In this method, the primary aromatic amine is reacted with the sodium nitrite in acidic medium to form a diazonium salt. This method is first used in the determination of dyes. PRINCIPLE The principle involved in this method is that the primary aromatic amine present in the sample reacts with the sodium nitrite in the presence of acid such as hydrochloric acid to obtain a diazonium salt. R − NH 2 + NaNO 2 +HCl R − N + ≡ N − Cl − + NaCl + H 2 O Sodium nitrite is added to the solution of amine in the presence of acid at 0–5 °C. The amine reacts with the nitrous acid to form nitrosamine, which is followed by the tautomerisation and the water mol

Electrogravimetry

Free pharmacy material Electrogravimetry INTRODUCTION Luckow first discovered the electrogravimetry for the determination of the copper. Then Alexander Classen first published the paper on the electrogravimetry in 1881. After that, Gibb's was the first founder of the electrogravimetry for the deposition of the metals on the mercury cathode. Electrogravimetry is a method for the separation of the metal ions by using the electrodes. The deposition takes place on the one electrode. The weight of this electrode is determined before and after deposition. This gives the amount of the metal present in the given sample solution. PRINCIPLE The main principle involved in this method is the deposition of the solid on an electrode from the analyte solution. Electrogravimeter The material is deposited by means of potential application. The electrons are transported to electrode by the following mechanisms: Diffusion Migration Convection THEORY A metal

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