What does the Langley index mean?
Thread Content
Dear friends: What does the Langley index refer to in circular water quality control? How to use it?
Determine the tendency to carbonate scaling! The Langley index is the difference between the measured pH value of the water sample and the saturated pH value (i.e., pHs). According to the expression: Is(Saturation Index) = pH – pHs; if Is is negative, then pH
This post was last edited by zhanyl628 on 2020-7-12 at 14:24. The pH value is related to factors such as the actual TDS, temperature, calcium hardness, and total alkalinity of circulating water; different formulas can be chosen based on the actual pH value. It can generally be calculated using lookup tables, or online calculation methods are also available. Additionally: the salt content should not be too high; generally, TDS should be < 4000 mg/L. Online calculation: http://www.ab126.com/Chemistry/3126.html?winzoom=1
The Langley index, also known as the saturation index and denoted by S.I., is the value obtained by subtracting the saturated pH value (PHs) from the measured pH value of the water sample. When calcium carbonate is at saturation in water, calcium bicarbonate does not decompose into calcium carbonate, nor does calcium carbonate continue to dissolve. The pH value at this point is known as the saturated pH value, denoted as PHs. If the pH value of the water sample is greater than PHS and the S.I. is positive, calcium carbonate will precipitate from the water; such water is considered scale-forming water ； When S.I. is negative, the existing scale layer is dissolved, exposing the raw material to erosion in water; such water is known as erosive water ； When S.I. is equal to zero, the water is in a saturated state, and such water is stable. The concepts of saturated PH and saturation index were proposed by Langelier to determine whether calcium carbonate scale will precipitate in water. Based on this, it is proposed to use acid or alkali addition as treatment methods to control the formation of scale. The Langelier saturation index (LSI for short) is an expression developed in 1936 by Langlier based on his theory of the dissolution equilibrium of carbonic acid in water; it represents the equilibrium relationship between solid calcium carbonate and carbon dioxide-containing solutions, and is calculated as the difference between the measured pH value of the water sample and the saturated pH value (i.e., pHs). According to the expression: Is(Saturation Index) = pH – pHs; if Is is negative, then pH
The applicability of the indications for LSI, as well as the LSI improved by carriers, is based on the following values; LSI denotes a saturated calcium carbonate (CaCO3) solution, and scale formation may occur. LSI (carrier) denotes -2,0
The Langley index, also known as the saturation index and denoted by S.I., is the value obtained by subtracting the saturated pH value (pHs) from the measured pH value of the water sample. When calcium carbonate is at saturation in water, calcium bicarbonate does not decompose into calcium carbonate, nor does calcium carbonate continue to dissolve. The pH value at this point is called the saturated pH value, denoted as pHs. If the pH value of the water sample is greater than pHS and the S.I. is positive, calcium carbonate will precipitate from the water; such water is considered scale-forming water ； When S.I. is negative, the existing scale layer is dissolved, exposing the raw material to erosion in water; such water is known as erosive water ； When S.I. is equal to zero, the water is in a saturated state, and such water is stable. The concepts of saturated pH and saturation index were proposed by Langelier to determine whether calcium carbonate scale will precipitate in water. Based on this, it is proposed to use acid or alkali addition as treatment methods to control the formation of scale
Is it reliable to use the Langley index to guide anti-corrosion efforts? Do you have any experience in this area? Thank you!
Moderator: Is it okay to use the Langley index theory to guide anti-corrosion work?
Hehe, you know me pretty well, huh； The Langley index only reflects the trend of carbonate scaling; good luck, young man!