| Introduction | | | | experimental sample can be determined. |
| Sodium Chloride determination | | | | Following the experiment in this report (to determine |
| Evaluation of salt concentration (sodium chloride) | | | | sodium chloride content in the sample), the salt is |
| present in foodstuffs is very important mainly for the | | | | initially required to be extracted from the food |
| reason of preservation and taste of the food | | | | sample (tomato ketchup) by means of accurate |
| products. | | | | ashing at 500 – 550°C (alkali chlorides are |
| Total chloride in the food is usually determined and | | | | virtually volatile at higher temperature) with |
| can be presented as sodium chloride content. | | | | subsequent dissolution of the ash. |
| Insignificant components of foods may also provide | | | | As mentioned earlier Mohr procedure involves direct |
| chloride ions but those food products to which salt is | | | | titration with 0.1M silver nitrate in which the chloride |
| added are essentially analysed for sodium chloride | | | | content is measured in the absence of acid. |
| content. | | | | - Titration Volhard method |
| Salt content of the food may be analytically | | | | Chloride ion can be determined by Volhard procedure |
| determined in one of the following ways: | | | | during which the food sample is boiled in diluted nitric |
| 1. Chemical techniques | | | | acid. The method involves the addition of excess |
| Titrimetric methods are the most widely used for salt | | | | silver nitrate and back titration with potassium |
| determination and are usually based on the following | | | | thiocyanate. |
| methods: | | | | Adding an excess of silver nitrate solution to a |
| - Titration Mohr method | | | | solution containing chloride ions, results in the |
| The Mohr method uses chromate ions as an indicator | | | | precipitation of silver chloride. |
| in the titration of chloride ions with a silver nitrate | | | | The concentration of chloride can then be analysed |
| standard solution. Following the precipitation of the | | | | by back-titrating of the excess (unreacted) silver ions |
| whole amount of chloride (usually as white silver | | | | with thiocyanate solution to create a silver |
| chloride) the first excess of titrant results in the | | | | thiocyanate precipitate. |
| production of a silver chromate precipitate, that | | | | Fe3+ (ferric ion) is usually used as an indicator for the |
| indicates the end point. | | | | titration because as soon as all the silver ions have |
| When the stoichiometry and moles consumed at the | | | | reacted, the minimum excess of thiocyanate will |
| end point are identified, the amount of chloride in the | | | | react with Fe3+ to produce a bright red complex. |