important, the mathematical calculations must be accurate.

It

is your responsibility to develop methods that ensure correct

calculations. Develop the habit of double-checking. Either you

or the technicians may perform this.

5.

Standardization and Classification

Standardized solutions that are made in the laboratory can be

broken down into two major categories:

a.

Primary standards.

Primary standards are substances

used as references.

The properties of these standards include

high millequivalent weights greater than 50, high degree of

stability and do not readily absorb atmospheric moisture.

Primary standards usually react completely when neutralized.

They are usually weak acids or bases. Examples of some primary

standards that you may find in the laboratory are KHP, Na2CO3,

and H2C2O4.

b. Secondary standards. Secondary standards function just

as well as primary substances, but there are differences in

their properties.

One main difference is unlike primary

standards, secondary standards are usually strong acids and

bases, and they have low millequivalent weight and are more

hazardous to handle. Examples of secondary standards are acids

such as Hydrochloric (HCL) and Sulfuric (H2SO4) and bases such

as Potassium Hydroxide (KOH) and Sodium hydroxide (NaOH).

6.

Calculations

Titration is a process that helps to determine the concentration

of unknown solution.

Comparing the volume of the unknown

solution with that of the standard does this.

Since the

concentration

of

the

standard

is

already

known,

the

concentration of the unknown may be calculated by applying the

following functions:

1a.

Normality = number of millequivalent weights

Number of milliliters of solution

1b.

Number of millequivalents = number of milliequivalents

`(Reaction 1) (Reaction 2)

1c.

Number of milliequivalents = Normality x milliliters

3-4

Integrated Publishing, Inc. |