Basic Chemistry UNITS of MEASUREMENT - Chemical Cleaning Chemistry Parameters - Engineering - http://maxpages.com/jpchemical/Basic_Chemistry

Understanding Water Quality and Water Solutions in Chemical Cleaning Introduction A basic knowledge of water quality is very important consideration in the design and operation of the system. Therefore, the ability to read and understand a water quality analysis is very useful Obtaining a Water Sample Glass or plastic containers are preferable for sample collection. For most analyses, the samples should be at least a pint. The containers should be thoroughly cleaned and rinsed before use to avoid contamination of the water sample. Sample bottles should be filled completely to the top (with all air removed), carefully labeled, and tightly sealed. Samples should be sent immediately to a water testing laboratory. For a chemical cleaning suitability analysis, the following tests should be requested from the laboratory, based on equipment to be cleaned, kind of cleaning, materials of the equipment, type of deposits to be removed: Concentration Volume Electrical Conductivity (EC) Total dissolved solids (TDS), Turbidity pH, iron 2, iron 3, iron total alkalinity, Chloride, Size of suspended solids Redox value Phosphates content Other parameters that are sometimes also needed to properly assess the suitability of chemical cleaning system Units Used in Water Analysis Concentration: One obstacle in interpreting a water analysis is that water testing laboratories report results in various units. For example, the concentration of chemical constituents may be reported as parts per million (ppm), milligrams per liter (mg/L), or milliequivalents per liter (meq/L). For many years, water analyses made in the U.S. were reported in parts per million (ppm). One ppm is equivalent to 1 mg of solute per kg of solution. Therefore, 1% is equal to 10,000 ppm. Parts per thousand (ppt, which is equivalent to 1 g solute per kg of solution) is frequently used to report salinity levels in sea water. In recent years, the development of more sensitive analytical equipment has led to terms such as parts-per-billion to report trace elements and pesticide concentrations. Concentration ppm = mg/L ppm = parts per million 1mg/L = 1,000 microgram/L mg/L = milligrams per liter 1ppm = 1,000ppb ppb = parts per billion 1% = 10,000ppm 1% = g/100mL ppt or 0/00 = parts per thousand 1ppt = 1,000ppm ppb = parts per billion 1% = 10ppt ug/g = microgram/gram 0.1% = 1g/L 1ug/g = 1ppm 1000ppb = 1ppm g/L = gram per liter Volume cc = ml cc = cubic centimeters ml = milliliters 1ml = 1g water g = gram 1cubic cm= 1cm3= 0.0610 in3 1 cubic decimetre= 1 dm3= 0.353 ft3 1 cubic meter=1m3= 1000 dm3= 1.3080 yd3 1 litre= 1 dm3= 1.76 pt= 2.113 US pt 1 pint= 0.56 litre= 20 ounces 1 ounce 28.413 ml 1 gallon= 4.546 litre 1 US ounce= 1,04 IMP ounce= 29,574 ml 1 US pint = 0.83 IMP pint= 0.47 litre 1 Us gallon= 0.93 IMP gallon= 3.78 litre Water Quality Parameters Acid An acid can be defined as a compound that releases hydrogen ions (H+) in a solution. All acids contain hydrogen. In general, acids have more or less a sour taste, they change litmus paper red, and they react with bases to form salts and water. An example is acetic acid (vinegar), which is considered a weak acid because it releases only small amounts of free hydrogen ions into solution. Sulfuric acid (H2SO4) is considered a strong acid because it releases more hydrogen ions into solution. Bases Bases are substances which can release hydroxyl (OH-) ions. Bases change litmus paper blue. As is the case with acids, bases demonstrate varying degrees of ionization (H- release). Those that ionize to a large extent are called strong bases, and those that ionize only slightly are known as weak bases. Salts A normal salt is a compound that is formed by the union of the cations (ions that carry a positive charge) of any base and anions (ions that carry a negative charge) of any acid. Other salts can be formed from acids or bases. Turbidity:Abbreviations NTU = nephelometric turbidity units FTU = formazin turbidity units JTU = jackson turbidity units FAU = formazin attenuation units (pertaining to readings taken with colorimeter) Water Hardness: Water hardness is the amount of dissolved in water. Hardness units ppm= total hardness in ppm Carbonate 1 ppm= 0.058 gpg (grains per usa gallon) 1ppm = 0.07 Clarc degrees 1ppm= 0.10 French degrees 1ppm= 0.056 German degrees 1gpg= 17.1 ppm 1gpg= 1.20 Clarc degrees 1gpg= 1.71 French degrees 1gpg= 0.958 German degrees 1 French degree= 17.84 German degrees 1 French degree= 10 ppm 1 German degree= 17.84 ppm Conductivity/TDS (total dissolved solids): Conductivity Units: uS = microSiemens = mhos/cm = micromhos per centimeter mS = milliSiemens = mmhos/cm = millimhos per centimeter (mhos and Siemens are the same) Alkalinity: Conversions Abbreviations 1dKh = 17.9ppm CaCO3 dKh = German degrees of hardness (also shown as Kh) 1 meq/L = 50ppm CaCO3 meq/L = milli equivalents per liter Weight., Conversion Factors, Abbreviations: 1milligram (mg)= 0,0154 grains 1 gram (g)= 1000 mg= 0.035 ounces (oz) 1 metric carat= 0,2 g= 3.08 grains 1 kilogram (kg)= 1000 g= 2.20 lb 1 tonne (t) = 1000 kg 1 ounce (oz) = 437,5 grains= 28.35 g 1 pound (lb) = 0.4536 kg Temperature: TEMPERATURE SCALES °C: degree Celsius (centigrade), °F: degree Fahrenheit, K: degrees Kelvin °Reaumur degrees °Rankine degrees Conversion Formulas a °C = (4/5)a °Reaumur = [32 + (9/5)a] °F b °Reaumur = (5/4)b °C = [32 + (9/4)b] °F c °F = (5/9)(c - 32) °C = (4/9)(c - 32) °Reaumur t °C = (t + 273.15) K TK K = (TK - 273.15) °C = [1.80 * (TK - 273.15) + 32] °F = 1.80 TK °Rankine (1.8 x °C) + 32 = °F (°F - 32) x 0.56 = °C -18 C= 0 F 0 C= 32 F 10 C= 50 F 50 C= 122F 100C= 212F Electrical Conductivity Electrical conductivity (EC) is a measure of the ability of water to pass an electrical current. Conductivity in water is affected by the presence of inorganic dissolved solids such as chloride, nitrate, sulfate, and phosphate anions or sodium, magnesium, calcium, iron, and aluminum cations. Organic compounds like oil, phenol, alcohol, and sugar do not conduct electrical current very well and therefore have a low conductivity when in water. Conductivity is also affected by temperature: the warmer the water, the higher the conductivity. For this reason, conductivity measurements are reported as conductivity at 25o C. EC measurements are taken with platinum electrodes and presented in units of conductance. The drop in voltage caused by the resistance of the water is used to calculate the conductivity per centimeter. The metric (SI) unit of measurement is deci-Siemens per meter (dS/m), which is equal in magnitude to the commonly used conductance term of millimho/cm (mmho/cm). Both of these terms are generally in the range of 0.1 to 5.0 for waters used for irrigation. Conductivity is also reported in units 1,000 times smaller: micromhos per centimeter (µmhos/cm) or microsiemens per centimeter (µS/cm). The conversion from electrical conductance to total dissolved solids (TDS) depends on the particular salts present in the solution. pH pH refers to water being either an acid, base, or neither (neutral). A pH of 7 is said to be neutral, a pH below 7 is ``acidic'' and a pH above 7 is ``basic'' or ``alkaline''. Like the Richter scale used to measure earthquakes, the pH scale is logarithmic. A pH of 5.5 is 10 times more acidic than water at a pH of 6.5. Thus, changing the pH by a small amount (suddenly) is more of a chemical change (and more stressful to fish!) than might first appear. The term pH is used to indicate the alkalinity or acidity of a substance as ranked on a scale from 1.0 to 14.0. The pH of water affects many chemical and biological processes in water. The pH scale measures the logarithmic concentration of hydrogen (H+) and hydroxide (OH-) ions, which make up water (H+ + OH- = H2O). When both types of ions are in equal concentration, the pH is 7.0 or neutral. The pH value is the negative power to which 10 must be raised to equal the hydrogen ion concentration. Mathematically this is expressed as: pH = -log [H+] Below 7.0, the water is acidic (there are more hydrogen ions than hydroxide ions). When the pH is above 7.0, the water is alkaline, or basic (there are more hydroxide ions than hydrogen ions). Since the scale is logarithmic, a drop in the pH by 1.0 unit is equivalent to a 10-fold increase in acidity. So, a water sample with a pH of 5.0 is 10 times as acidic as one with a pH of 6.0, and pH 4.0 is 100 times as acidic as pH 6.0. Generally, pH can be analyzed in the field or in the lab. If it is analyzed in the lab, pH must be measured within 2 hours of sample collection. The pH of a sample can change due to carbon dioxide from the air dissolving into the water. Raising and Lowering pH One can raise or lower pH by adding chemicals. Because of buffering, however, the process is difficult to get right. Increasing or decreasing the pH (in a stable way) actually involves changing the KH. The most common approach is to add a buffer (in the previous section) whose equilibrium holds the pH at the desired value. Muriatic (hydrochloric) acid can be used to reduce pH. Note that the exact quantity needed depends on the water's buffering capacity. In effect, you add enough acid to use up all the buffering capacity. Once this has been done, decreasing the pH is easy. Alkalinity Alkalinity is primarily determined by the presence of bicarbonates (HCO3-), carbonates (CO3-), and hydroxides (OH-) in water. Alkalinity is a measure of the capacity of water to neutralize acids. Alkaline compounds in the water, such as bicarbonates (baking soda is one type), carbonates, and hydroxides, remove H+ ions and lower the acidity of the water (which translates to increased pH). They usually do this by combining with the H+ ions to make new compounds. Without this acid-neutralizing capacity, any acid added to a water source would cause an immediate change in the pH. Total alkalinity is determined by measuring the amount of acid (e.g. muriatic acid) needed to bring the sample to a pH of 4.2. At this pH, all the alkaline compounds in the sample are "used up". The result is reported as milligrams per liter of calcium carbonate (mg/L of CaCO3). Alkalinity expressed as mg/L of CaCO3 can be converted to an equivalent concentration of HCO3- by dividing by 0.82 Hardness The term "hardness" is one of the oldest terms used to describe characteristics of water. In fact, Greek philosopher Hippocrates (450-354 B.C.) used the "hard" and "soft" terms in a discourse on water quality. He state "Consider the waters which the inhabitants use, whether they be marshy and soft, or hard and running from elevated and rocky situations ...". The hard term most likely referred to the condition of water which originated in the limestone formations of the upland regions. Over the years, hardness has come to be associated with the soap-consuming property of water or with the encrustations resulting from hard water when it is heated. General hardness (GH) refers to the dissolved concentration of magnesium and calcium ions. When fish are said to prefer ``soft'' or ``hard'' water, it is GH (not KH) that is being referred to. Note: GH, KH and pH form the Bermuda's Triangle of water chemistry. Although the three properties are distinct, they all interact with each other to varying degrees, making it difficult to adjust one without impacting the other. That is one reason why beginning aquarists are advised NOT to tamper with these parameters unless absolutely necessary. As an example, ``hard'' water frequently often comes from limestone aquifers. Limestone contains calcium carbonate, which when dissolved in water increases both the GH (from calcium) and KH (from carbonate) components. Increasing the KH component also usually increases pH as well. Conceptually, the KH acts as a ``sponge'' absorbing the acid present in the water, raising the water's pH. Water hardness follows the following guidelines. The unit dH means ``degree hardness'', while ppm means ``parts per million'', which is roughly equivalent to mg/L in water. 1 unit dH equals 17.8 ppm CaCO3. Most test kits give the hardness in units of CaCO3; this means the hardness is equivalent to that much CaCO3 in water but does not mean it actually came from CaCO3. Hardness in water is caused primarily by calcium and magnesium, although iron and manganese also contribute to the actual hardness. Hardness may be divided into two types: carbonate and noncarbonate. Carbonate hardness is that portion of calcium and magnesium that can combine with bicarbonate to form calcium and magnesium carbonate. If the hardness exceeds the alkalinity (expressed as mg/L CaCO3), the excess is termed noncarbonate hardness. The carbonate hardness is an indicator of the potential for calcium carbonate precipitation and scale formation. Total hardness (carbonate and noncarbonate) is customarily expressed as equivalents of calcium carbonate (CaCO3). Since the formula weight of CaCO3 is near 100, hardness expressed in terms of mg/L of CaCO3 can be converted to meq/L by dividing by 50. Hardness can be calculated from individual concentrations of calcium and magnesium using Equation . H = 2.5 Ca + 4.1 Mg where, H = total hardness (mg/L as CaCO3) Ca = calcium concentration (mg/L of Ca) Mg = magnesium concentration (mg/L of Mg) Total Solids Total solids are dissolved solids plus suspended and settle-able solids in water. In stream water, dissolved solids consist of calcium, chloride, nitrate, phosphorus, iron, sulfur, other ions, and particles that will pass through a filter with pores of approximately 2 microns (0.002 cm) in size. Suspended solids include silt and clay particles, plankton, algae, fine organic debris, and other particulate matter. These are particles that will not pass through a 2-micron filter.

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