re" of the
sample.

ALKALIES AND ALKALI SALTS.

Care should be bestowed upon the sampling of solid caustic soda or
potash as the impurities during the solidification always accumulate in
the centre of the drum, and an excess of that portion must be avoided or
the sample will not be sufficiently representative. The sampling should
be performed expeditiously to prevent carbonating, and portions placed
in a stoppered bottle. The whole should be slightly broken in a mortar,
and bright crystalline portions taken for analysis, using a stoppered
weighing bottle.

_Caustic Soda and Caustic Potash._--These substances are valued
according to the alkali present in the form of caustic (hydrate) and
carbonate.

About 2 grammes of the sample are dissolved in 50 c.c. distilled water,
and titrated with N/1 sulphuric acid, using phenol-phthalein as
indicator, the alkalinity so obtained representing all the caustic
alkali and one-half the carbonate, which latter is converted into
bicarbonate. One c.c. N/1 acid = 0.031 gramme Na_{2}O or 0.040 gramme
NaOH and 0.047 gramme K_{2}O, or 0.056 gramme KOH.

After this first titration, the second half of the carbonate may be
determined in one of two ways, either:--

(1) By adding from 3-5 c.c. of N/10 acid, and well boiling for five
minutes to expel carbonic-acid gas, after which the excess of acid is
titrated with N/10 soda solution; or

(2) After adding two drops of methyl orange solution, N/10 acid is run
in until the solution acquires a faint pink tint.

In the calculation of the caustic alkali, the number of c.c. of acid
required in the second titration, divided by 10, is subtracted from that
used in the first, and this difference multiplied by 0.031, or 0.047
gives the amount of Na_{2}O or K_{2}O respectively in the weight of
sample taken, whence the percentage may be readily calculated.

The proportion of carbonate is calculated by multiplying the amount of
N/10 acid required in the second titration by 2, and then by either
0.0031 or 0.0047 to give the amount of carbonate present, expressed as
Na_{2}O or K_{2}O respectively.

An alternative method is to determine the alkalinity before and after
the elimination of carbonate by chloride of barium.

About 7-8 grammes of the sample are dissolved in water, and made up to
100 c.c., and the total alkalinity determined by titrating 20 c.c. with
N/1 acid, using methyl orange as indicator. To another 20 c.c. is added
barium chloride