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1. Precipitate the magnesium with sodium hydrogen phosphate, or 
with ammonium sodium hydrogen phosphate, rather than with ammonium 
phosphate. 
2. Do not neglect to wash the precipitate with water containing one- 
fourth its volume of cone. ammonium hydroxide until the washings show 
but a faint turbidity with silver nitrate acidified with nitric acid. If 
ammonium phosphate is present thorough washing is particularly im- 
portant. 
3. Remove the main portion of the residue from the paper before in: 
cinerating. or burn the paper with a small residue, in the crucible, over a 
very small Bunsen flame. This may be quickly accomplished in a draught 
produced by tilting the lid of the crucible. Do not ignite strongly nor heat 
to the fusing peint of the phosphate until the material in the crucible is 
white (carbon free). If the ashing of the paper has been imperfect, allow 
the crucible to coel, moisten the residue with a few drops of cone. nitric 
acid, cover the crucible with the lid, carefully evaporate the acid and heat 
again in the Bunsen flame. The process must be repeated until the residue 
becomes white. a 
4. To the residue in the crucible add the main portion of the pre- 
cipitate and heat in the Bunsen flame gently at first, or until the greater 
part of the ammonia has been expelled, then heat strongly in the blast 
flame until the material «eases to decrease in weight. 
