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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This science article is a stub. It is based on the fact that silver salt of an organic acid on heating gives residue of metallic silver. Carbon disulphide test When sodium bromide and sodium iodide in the Lassaignr extract is treated with chlorine water, the bromide and iodide oxidise to the corresponding halogens.

This halogen dissolves in carbon disulphide.

Halogens present in an organic compound forms sodium halide on fusion with sodium metal. Separation of mixture of amines: Platinichloride method for bases: During the preparation of Lassaigne’s extract, chlorine form the organic compound reacts with sodium to form lassaibne chloride.

The carbon and nitrogen present in the organic compound on fusion with sodium metal gives sodium cyanide NaCN soluble in water.

Sodium fusion test

Soluble in both ether and water. Orange — red azo dye indicates the laszaigne of a primary aromatic amine. Mass of the organic substance.

A mixture of toluene may be separated by extraction with dilute HCl; the aniline passes into the aqueous layer in the form of the salt aniline hydrochloride and may be recovered by neutralization. Sodium cyanide is converted to sodium ferrocyanide on treating with ferrous sulphate. The solution is then filtered and the halide is precipitated with silver nitrate solution.



Then the solution is diluted to ml and keep in a slightly stoppered bottle. Diethyl Ketone and Acetic Acid: Ferric ions generated during the process react with ferrocyanide to form prussian blue precipitate of ferric ferrocyanide.

Carbon is the main constituent element of all organic compounds. Saturated aliphatic hydrocarbons, aromatic hydrocarbons, halogen, derivative of hydrocarbons, diaryl ethers. As the addition of chlorine water is continued, the purple colour disappears owing to oxidation of iodine to iodate and if bromine is present, is present, is replaced by a brown or reddish colour. From the mass of silver halide formed, the percentage of the halogen can be calculated. 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.

The filtrate is acidified with dil.

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

Sodium chloride gives a white precipitate of silver chloride with silver nitrate solution. Students understand various tests to detect the presence of nitrogen, sulphur and halogens in an organic compound. Solution is cooled and poured continuously into aqueous Na 2 CO 3 solution contained in an evaporating dish.

Our IITian faculty will contact you in 1 working day. A method of testing for the presence of a halogen, nitrogen, or sulphur in an organic compound. Organic Chemistry Revision Notes. If there is apparently no evolution of nitrogen gas from clear solution. In this test, the organic compound is fused with metallic sodium to convert these elements into water soluble sodium salt.


The hydrogen chloride formed gives white fumes of ammonium chloride with ammonium hydroxide. The molecular mass of an acid can be determined with the help of the following relationship, Mol. Views Read Edit View history. A known volume of the gaseous hydrocarbon is mixed with an excess known or unknown volume of oxygen in the eudiometer tube kept in a trough of mercury.

Separate based on Differences in the vaolalities of the component in aqueous solution: The actual method used involves the following steps, A known volume of the gaseous hydrocarbon is mixed with an excess known or unknown volume of oxygen in the eudiometer tube kept in a trough of mercury.

Lassaigne Method | Determination of Molecular Mass-Askiitians

Chemical classification of the amine function: August Click [show] for important translation instructions. Do not translate text that appears unreliable or low-quality.

Students understand the chemical reactions and their balanced equations that takes place during each test. A sweet, fruity lsasaigne of an ester confirms the presence of ester. Let E be the equivalent mass of the base. It is then reduced to NTP conditions. Contraction on explosion and cooling. Calculation of Empirical and Molecular Formula. It is then filtered, cooled and treated with ammoniacal silver nitrate solution and heated in a water bath; white to grey and then black precipitate formation confirms the presence of the nitro group.