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Hanna Instruments Australia
Sales: (03) 9769 0666   |    Mon to Fri: 8:30am – 5:00pm

Measuring Acidity of Natural Water by Titration

In the past 75 years, the worldwide human population has increased from approximately 2.5 billion to over 7 billion people. Population increase, the resulting increase in use of natural resources, and anthropogenic (human) produced waste have significantly impacted our natural environment. One of the most vital resources that humans require to live is water. Ironically enough, one of the most common anthropogenic effects on the environment is pollution of water. One indication of water pollution is a high acidity level. Water bodies in Australia and all around the world consist of varying levels of acidity due to natural factors such as landscape position and slope, watershed size, geology, and soil composition, as well as anthropogenic pollution.

Acidity, the buffering capacity of a substance to resist a change in pH when reacted with a strong base, is determined by titration with sodium hydroxide (NaOH) and commonly expressed as mg/L or meq/L calcium carbonate (CaCO₃). Acidity of water originates from various sources: weak organic acids, such as dissolved CO₂ as carbonic acid, acetic acid, and tannic acid; strong mineral acid, such as sulfuric and hydrochloric acids; and metal salts from iron, aluminium, and manganese. High levels of strong mineral acids are indicative of anthropogenic pollution. When atmospheric pollutants from the burning of fossil fuels, such as sulphur dioxide (SO₂) and nitrogen oxides (NOx), are emitted into the atmosphere, they combine with water and ozone to become sulfuric and nitric acid. During precipitation events, these acidic counterparts are then deposited on the ground and in water bodies in the form of “acid rain.” Improperly managed mining activities also contribute to acidity levels, where acid mine drainage releases metals and acids into surrounding water systems. High levels of water acidity affect various aspects of the water body’s ecosystem, from chemical reaction rates to biological processes in almost every living organism. Fish, specifically, can only withstand a very narrow range of acidity before biological processes are affected and fatality occurs. If the water body is used for drinking water treatment, high acidity and a low pH can lead to pipe corrosion.

There are many important parameters to be measured to determine water quality: while pH, temperature or dissolved oxygen can be monitored directly in the field, testing acidity is often performed in a lab by manual titration with an indicator dye. Hanna’s HI902 Potentiometric Titrator operates under the same principles as the manual titration, with options for fixed pH endpoints at 3.7 pH for strong acidity (methyl orange acidity) and 8.3 pH for total acidity (phenolphthalein acidity). The HI902 offers increased accuracy and repeatability compared to manual titration. This is due to the use of the HI1131B Combination pH Electrode to determine the precise pH endpoint, and the high accuracy titrant volume dosing burette. The HI902 also offers more in terms of capability; Alkalinity, Chloride, Flouride, Ammonia, Nitrates, Permanganate Index, Calcium & Magnesium Hardness, Total Hardness and Chemical Oxygen Demand. All your water testing requirements in the one compact unit.

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