What is lassaigne's test?

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, nitrogen, and sulphur, in an organic compound. ... The test involves heating the sample strongly with clean sodium metal, "fusing" it with the sample.

The Lassaigne's test, also known as 

the sodium fusion test, is used in 

elemental analysis to determine the 

presenceof foreign elements,

 specifically halogens, nitrogen, and 

sulfur, in an organic compound.

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"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"