2NaHO + H_{2}SO_{4} = Na_{2}SO_{4} + 2H_{2}O.
Acids like sulphuric acid are termed bibasic, and their equivalent is
only half the molecular weight. Thus, a normal solution of sulphuric
acid would contain 49 grams (98/2) of real acid per litre. Similarly,
lime and most of the bases are bibasic, as may be seen from the
following equations; hence their equivalent will be half the molecular
weight.
2HCl + CaO = CaCl_{2} + H_{2}O.
2HCl + MgO = MgCl_{2} + H_{2}O.
_The standard normal solution of hydrochloric acid_ is made by diluting
100 c.c. of the strong acid to one litre with water. This will be
approximately normal. In order to determine its exact strength, weigh up
3 grams of recently ignited pure sodium carbonate or of the ignited
bicarbonate. Transfer to a flask and dissolve in 200 c.c. of water; when
dissolved, cool, tint faintly yellow with a few drops of a solution of
methyl orange, and run in the standard "acid " from a burette till the
yellow changes to a pink. Read off the number of c.c. used, and
calculate to how much sodium carbonate 100 c.c. of the "acid" are
equivalent. If the "acid" is strictly normal, this will be 5.3 grams. It
will probably be equivalent to more than this. Now calculate how much
strictly normal "acid" would be equivalent to the standard found. For
example: suppose the standard found is 5.
Pages:
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602