------------------------------------------------------------------------- | | Composition of the solution in gram-molecules | | to 1000 gram-molecules Point. | Solid phases. | of water. | |---------------------------------------------- | | NaHCO_{3} | NaCl | NH_{4}HCO_{3} | NH_{4}Cl ------------------------------------------------------------------------- -- | NaHCO_{3} | 1.08 | -- | -- | -- -- | NaCl | -- | 6.12 | -- | -- -- | NH_{4}HCO_{3} | -- | -- | 2.36 | -- -- | NH_{4}Cl | -- | -- | -- | 6.64 I. | NaHCO_{3}; NaCl | 0.12 | 6.06 | -- | -- II. | NaCl; NH_{4}Cl | -- | 4.55 | -- | 3.72 III. | NH_{4}Cl; | -- | -- | 0.81 | 6.40 | NH_{4}HCO_{3} | | | | IV. | NaHCO_{3}; | 0.71 | -- | 2.16 | -- | NH_{4}HCO_{3} | | | | P_{1} | NaHCO_{3}; | 0.93 | 0.51 | -- | 6.28 | NH_{4}HCO_{3}; | | | | | NH_{4}Cl | | | | P_{2} | NaHCO_{3}; | 0.18 | 4.44 | -- | 3.73 | NaCl; NH_{4}Cl | | | | ------------------------------------------------------------------------- With reference to the solution represented by the point P_{1}, it may be remarked that it is an incongruently saturated solution (p. 279). If sodium chloride is added to this solution, the composition of the latter undergoes change; and if a sufficient amount of the salt is added, the solution P_{2} is obtained. Turning now to the practical application of the data so obtained, consider first what is the influence of concentration on the yield of soda. Since the reaction consists essentially in a double decomposition between sodium chloride and ammonium bicarbonate, then, after the deposition of the sodium bicarbonate, we obtain a solution containing sodium chloride, ammonium chloride, and sodium bicarbonate. In order to ascertain to what extent the sodium chloride has been converted into solid sodium bicarbonate, it is necessary to examine the composition of the solution which is obtained {323} with definite amounts of sodium chloride and ammonium bicarbonate. [Illustration: FIG. 127.]