Description

Sodium (Na) is the third element in Group IA of the periodic table. It has an atomic number of 11, an atomic weight of 22.99, and a valence of 1. The average abundance of Na in the earth’s crust is 2.5%; in soils it is 0.02 to 0.62%; in streams it is 6.3 mg/L, and in groundwaters it is generally >5 mg/L. Sodium occurs with silicates and with salt deposits. Sodium compounds are used in many applications, including caustic soda, salt, fertilizers, and water treatment chemicals.

Sodium is very soluble, and its monovalent ion Na⁺ can reach concentrations as high as 15 000 mg/L in equilibrium with sodium bicarbonate. The ratio of sodium to total cations is important in agriculture and human physiology. Soil permeability can be harmed by a high sodium ratio. In large concentrations it may affect persons with cardiac difficulties. A limiting concentration of 2 to 3 mg/L is recommended in feedwaters destined for high-pressure boilers. When necessary, sodium can be removed by the hydrogen-exchange process or by distillation. The U.S. EPA advisory limit for sodium in drinking water is 20 mg/L.

Scope

Analysts, researchers, and regulators have relied on this peer-reviewed publication since 1905. The trusted source of accurate, proven methodology for analyzing natural waters, water supplies, and wastewaters.

The 23rd edition of Standard Methods for the Examination of Water and Wastewater® contains over 400 laboratory methods for the analysis of:

• Dissolved Solids
• Metals
• Free and Total Chlorine
• Odor, Taste, and Flavor Profile Analysis
• Disinfection By-products
• Radionuclides
• Total Organic Carbon
• Total and Fecal Coliform

Laboratories worldwide rely on this comprehensive reference as the trusted source of accurate, proven methodology for analysis of water, water supplies, and wastewater. It is the essential resource for water analysis professionals.

The methods in the 23rd edition (as in previous editions) are believed to be the best available, generally accepted procedures for analyzing water, wastewater, and related materials. They represent the recommendations of specialists, ratified by a large number of analysts and others of more general expertise, and as such are truly consensus standards, offering a valid and recognized basis for control and evaluation. All methods are dated to identify which ones changed significantly between editions.

New in the 23rd edition

• Over 80 revised methods and 5 new methods added
• Extensive revisions to Microbiological Examination (Part 9000)
• New drinking water method to test for pharmaceuticals and personal care products
• New, more realistic, visuals to help identify aquatic organisms
• Revisions to Solids, Cyanide, Nitrate, Dissolved Oxygen, and Biochemical Oxygen Demand