what is Solution

Different types of  Solution

Normal Solutions—Normal solutions are solutions that contain 1 gram equivalent weight of the active substance in each 1000 mL of solution; that is, an amount equivalent to 1.0079 g of hydrogen or 7.9997 g of oxygen. Normal solutions and solutions bearing a specific relationship to normal solutions, and used in volumetric determinations, are designated as follows: normal, 1 N; double-normal, 2 N; half-normal, 0.5 N; tenth-normal, 0.1 N; fiftieth-normal, 0.02 N; hundredth-

normal, 0.01 N; thousandth-normal, 0.001 N.

 

Molar Solutions—Molar solutions are solutions that contain, in 1000 mL, 1 gram-molecule of the reagent. Thus, each liter of a molar solution of sulfuric acid contains 98.07 g of H2SO4  and each liter of a molar solution of potassium ferricyanide contains 329.25 g of K3Fe(CN)6. Solutions containing, in 1000 mL, one-tenth of a gram-molecule of the reagent are designated “tenth-molar,”

0.1 M; and other molarities are similarly indicated.

 

Empirical Solutions—It is frequently difficult to prepare standard solutions of a desired theoretical normality, and this is not essential. A solution of approximately the desired normality is prepared  and standardized by titration against a primary standard solution. The normality factor so obtained  is used in all calculations where such empirical solutions are employed. If desired, an empirically prepared solution may be adjusted downward to a given normality provided it is strong enough to permit dilution.

All volumetric solutions, whether made by direct solution or by dilution of a stronger solution, must be thoroughly mixed by shaking before standardization. As the strength of a standard solution may change upon standing, the factor should be redetermined frequently.

When solutions of a reagent are used in several normalities, the details of the preparation and standardization are usually given for the normality most frequently required. Stronger or weaker solutions are prepared and standardized in the same general manner as described, using proportionate amounts of the reagent. It is possible in many instances to prepare lower normalities accurately by making an exact dilution of a stronger solution. Volumetric solutions prepared by dilution should be restandardized either as directed for the stronger solution or by comparison with another volumetric solution having a known ratio to the stronger solution.

Dilute solutions that are not stable, as, for instance, potassium permanganate 0.01 N and more dilute sodium thiosulfate, are preferably prepared by exactly diluting the higher normality with thoroughly boiled and cooled water on the same day they are required for use.