Section II. GRADES OF LABORATORY WATER
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
2-13. MINIMUM SPECIFICATIONS FOR THE THREE TYPES OF WATER
Silicate, mg/dL, maximum
Heavy metals, mg/dL, maximum,