~--To the filtrate from the lime add phosphate of soda. Allow
to stand overnight, filter, wash with dilute ammonia, dry, ignite, and
weigh as pyrophosphate.
~Sulphuric Oxide.~--To the remaining 250 c.c. of the filtrate from the
"insoluble," add an excess of barium chloride. Collect, wash, dry,
ignite, and weigh the barium sulphate.
~Sodium.~--It is estimated by difference.
The following may be taken as an example:--
Moisture 0.35
Insoluble matter 0.40
Lime 0.40
Magnesia 0.05
Sulphuric oxide 0.60
Chlorine 59.60
Sodium 38.60
------
100.00
POTASSIUM.
Potassium occurs in nature as chloride, in the mineral sylvine (KCl),
and more abundantly combined with magnesium chloride, in earnallite
(KCl.MgCl_{2}.6H_{2}O). It occurs as nitrate in nitre (KNO_{3}), and as
silicate in many minerals, such as orthoclase (or potash-felspar) and
muscovite (or potash-mica).
Potassium compounds are detected by the characteristic violet colour
they impart to the flame. The presence of sodium salts masks this tint,
but the interference can be neutralised by viewing the flame through a
piece of blue glass. Viewed through the spectroscope, it shows a
characteristic line in the red and another in the violet.
Pages:
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625