5 grams of the sample, dissolve in
water, and make up to 500 c.c. Take 50 c.c., tint with methyl orange,
and titrate with the normal solution of acid. The c.c. of acid used
multiplied by 2 gives the percentage of available alkali calculated as
potash (K_{2}O).
~Soda.~--This is calculated indirectly in the following way:--Deduct
from the potassium found the quantity required for combination with the
chlorine and sulphuric oxide present, and calculate the remainder to
potash (K_{2}O). The apparent surplus excess of available alkali is the
measure of the soda present.
~Carbon Dioxide.~--The c.c. of acid used in the available alkali
determination, multiplied by 2.2 and divided by 2.35, gives the
percentage of carbon dioxide.
LITHIUM.
Lithia, the oxide of lithium (Li_{2}O), occurs in quantities of 3 or 4
per cent. in various silicates, such as lepidolite (or lithia-mica),
spodumene, and petalite. It also occurs as phosphate in triphyline. It
is a constituent of the water of certain mineral springs. A spring at
Wheal Clifford contained as much as 0.372 gram of lithium chloride per
litre. In small quantities, lithia is very widely diffused.
The ~Detection~ of lithia is rendered easy by the spectroscope; its
spectrum shows a red line lying about midway between the yellow sodium
line and the red one of potassium.
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