Why are a calico strainer and chloroform used in a British Pharmacopoeia assay of milk of magnesia? The following is an assay for milk of magnesia in the British Pharmacopoeia (emphasis added):


  Dissolve the sodium hydroxide in $\pu{150 cm^3}$ of purified water, add the light magnesium oxide, mix to form a smooth cream and then add sufficient purified water to produce $\pu{2500 cm^3}$. Pour this suspension in a thin stream into a solution of the magnesium sulfate in $\pu{2500 cm^3}$ of purified water, stirring continuously during the mixing. Allow the precipitate to subside, remove the clear liquid, transfer the residue to a calico strainer, allow to drain and wash the precipitate with purified water until the washings give only a slight reaction for sulfate. Mix the washed precipitate with purified water, dissolve the chloroform in the mixture.


What is a calico strainer, and why is it used here? Is it better than using, say, Büchner filtration?

As well, why is chloroform used (see emphasized text, above)?
Ok I understand where you got chloroform from.

This is not the assay of milk of magnesia, but the extemporaneous preparation.

In extemporaneous preparations chloroform is used as:


a general anaesthetic
a carminative
flavouraing agent
preservative 


So in the case of mik of magnesia it has two main roles that is a carminative and a preservative.

Hope this helps