When iron and manganese are present, the filtrates are treated with bromine.
The reaction is, however, generally applicable to filtrates of bacterial cultures and could be used if needed.
Cool the mixture and filter; wash the residue with strong alcohol, and mix the filtrates.
The three filtrates from these three extractions were precipitated separately by lead acetate in 50 per cent.
These filtrates are in fact opalescent from the presence of a portion of nitrate in a colloidal (hydrated) form.
On long-continued boiling a further precipitation is determined, the filtrates from which are clear.