Section II. Grades of Laboratory Water

Section II. GRADES OF LABORATORY WATER

2-9.

DISCUSSION

Tap water contains various impurities, both organic and inorganic. These

impurities may interfere with many of the chemical tests that are routinely performed

and consequently contributed to invalid test results. For example, calcium is a

commonly performed laboratory test, and some tap water contains considerable

amounts of calcium. To eliminate the possibility of interfering substances in water,

either deionized or distilled water must be used in the preparation of all standards and

reagents. Water for use in the laboratory is broken down into three basic types: Type I,

Type II, and Type III.

2-10. TYPE I WATER

This is the purest type of water and is used for laboratory tests where the

greatest accuracy is desired. This type of water is designed for use with atomic

absorption, flame photometry, pH determinations, and fluorometry.

2-11. TYPE II WATER

This type of water is for general laboratory use and can be used for any type of

laboratory determination that does not specify Type I water. Of the type of procedures

listed under Type I water, only atomic absorption and fluorometry require the use of

Type I water.

2-12. TYPE III WATER

Type III water is used for rinsing glassware and is suitable for most qualitative

determinations.

2-13. MINIMUM SPECIFICATIONS FOR THE THREE TYPES OF WATER

Specifications

III

Specific conductance microhms, maximum

0.1

2.0

5.0

Specific resistance megohms, minimum

10.0

0.5

0.2

Silicate, mg/dL, maximum

0.01

Heavy metals, mg/dL, maximum,

0.01

Permanganate reduction

pass

test

MD0837

2-4