Heat gently, to drive off the
ammonic chloride, and ignite to a little below redness. Cool and weigh.
The residue consists of the mixed alkaline chlorides.
~Separation of the Alkali-Metals from each other.~--Sodium and lithium
are separated from the other alkali-metals by taking advantage of the
solubility of their chlorides in the presence of platinic chloride; and
from one another by the formation of an almost insoluble lithic
phosphate on boiling with a solution of sodium phosphate in a slightly
alkaline solution. C?sium, rubidium, and potassium yield precipitates
with platinic chloride, which are somewhat soluble, and must be
precipitated from concentrated solutions. C?sium and rubidium are
separated from potassium by fractional precipitation with platinum
chloride. Their platino-chlorides, being less soluble than that of
potassium, are precipitated first. One hundred parts of boiling water
dissolve 5.18 of the potassium platino-chloride, 0.634 of the rubidium
salt, and 0.377 of the corresponding c?sium compound. The separation of
lithium, c?sium, and rubidium is seldom called for, owing to their
rarity. The details of the separation of potassium from sodium are
described under _Potassium_. Ammonia compounds are sharply marked off
from the rest by their volatility, and it is always assumed that they
have been removed by ignition; if left in the solution, they would count
as potassium compounds.
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