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The sodium fusion test, or Lassaigne’s test, is used in elemental analysis for the qualitative determination of the presence of foreign elements, namely halogens. A method of testing for the presence of a halogen, nitrogen, or sulphur in an organic compound. A sample is heated in a test tube with a pellet of sodium. The hot. A drop of ferric chloride is added to this solution. A prussian-blue precipitate of ferric ferrocyanide, Fe4[Fe(CN)6]3 is formed. The formation of the prussian blue.

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Carbon is the main constituent element of all organic compounds.

Sodium fusion test

The various methods commonly employed for the estimation of principal elements are discussed in the table. Mass of the organic substance.

Thus, Equivalent mass of silver salt. Concentrated H 2 SO 4 dissolves only the dibutyl ether and it may be recovered from solution by dilution tfst water.

Detection of Elements: Lassaigne’s Test (Theory) : Class 11 : Chemistry : Amrita Online Lab

Test for Halogens Nitrogen and Sulphur absent A portion of the fusion solution is acidified with dilute nitric acid and then excess of silver nitrate solution is added. Occasionally the precipitate is oily at first but this becomes crystalline upon standing. Pressure after deducting aqueous tension. The halogens, nitrogen and sulphur are covalently bonded to the organic compounds.

The mother liquor is decanted lassainge the precipitate is treated with dilute aqueous ammonia solution. The steps lassajgne in the calculation are as follows. The most important basic nitrogen compounds are the primary, secondary and tertiary amines and they dissolve in mineral acids and change red litmus to blue.


Studying in Grade 6th to 12th? The filtrate is acidified with dil. Lassaigne in this edit is translated from the existing German Wikipedia article at [[: When an organic compound containing sulphur is heated with fuming nitric acid, sulphur is oxidised to sulphuric acid.

If a transient or permanent colouration usually purple, blue or green other than yellow or orange is observed, the substance probably a phenol or an enol.


The formation of a coloured eg. This page was last edited on 5 Julyat The method is based on the fact that when an organic compound containing halogen Cl, Br, or I is heated in a sealed tube with fuming nitric acid in presence of silver nitrate, silver halide is formed.

The alcoholic group can be detected by the following tests: During the preparation of Lassaigne’s extract, chlorine form the organic compound reacts with sodium to form sodium chloride. An unleagetn odour confirms the presence of primary amine.

Soluble in both ether and water. Aldehydes and Ketones from toehr liquid hydrocarbons and other neutral liquid compound e.

Lassaigne Method | Determination of Molecular Mass-Askiitians

If the compound is sparingly soluble in water a hot saturated aqueous solution is prepare and filtered. If a clear solution is obtained with a continuous evolution of nitrogen gas the substance is a primary amine. This science article is a stub. Separation of mixture of amines: You can help Wikipedia by expanding it. Oassaigne from ” https: Sodium cyanide is converted to sodium ferrocyanide on treating with ferrous sulphate.


Primary amines, secondary aliphatic and aryl-alkyl amines, Hydrizines. If the precipitate is white and readily soluble in ammonia solution, chlorine is present; if it is pale yellow and difficulty soluble, bromine is present; if it yellow and insoluble, then iodine and bromine may be confirmed by the following test.

Sodium sulphide formed during the preparation of Lassaigne’s extract reacts with lead acetate to yield lead sulphide as black precipitate. The precipitate is soluble in ammonium hydroxide. A drop of the given liquid or a crystal if solid is placed on a moist blue litmus paper. Here in this type of cases, both sulphur and nitrogen are to be identified in separate tests.

Quantitative Analysis of Organic Compounds Estimation of Elements After qualitative analysis of elements, the next step in the determination of molecular formula of an organic compound is the estimation of various elements by mass, i. Lead acetate lassainge Sodium sulphide formed during the preparation of Lassaigne’s extract reacts with lead acetate to yield lead sulphide as black precipitate.

Views Read Edit View history. Calculation of empirical formula: In the preparation of silver salt, a hydrogen atom of the carboxylic group is replaced by a silver atom. Search within my subject specializations: Reference books of Organic Chemistry. The magnesium ammonium phosphate is washed, dried and ignited when it is converted to magnesium pyrophosphate.