Solubility Of Salts

Basic concepts of salt solubility and the concept of solubility product were discussed in Sec. 2.13. Consideration of solubility relationships can aid in understanding the natural forces that dissolve rocks and other minerals, bringing minerals into aqueous solution. Variations in mineral characteristics of water can also be understood to some degree by considering the factors affecting solubility of minerals. Knowledge of solubility relationships can also help to devise methods for treating...

Problems

17.1 What causes acidity in natural waters 17.2 (a) What pH range is used to measure mineral acidity in water (ib) What pH range is used to measure total acidity in water (c) How are methyl orange and phenolphthalein acidity related to mineral and total acidity . 17.3 Why may we be concerned with acidity in water 17.4 Can the pH of a water sample be calculated from a knowledge of its acidity Why 17.5 Can the carbon dioxide content of a waste sample known to contain a significant concentration...

Other Considerations

A number of situations are encountered in practice that involve carbon dioxide-alkalinity-pH relationships and deserve some explanation. It is common practice to aerate water to remove carbon dioxide, ammonia, and volatile organic chemicals. Since carbon dioxide is an acidic gas, its removal tends to decrease H+ and thus raise the pH of the water in accordance with Eq. (18.17). Normai air contains about 0.035 percent by volume of carbon dioxide, which is equivalent to lO3 46 atm at sea level....

Methods Of Measurement

Both carbon dioxide and mineral acidity can be measured by means of standard solutions of alkaline reagents. Mineral acids are measured by titration to a pH of about 3.7, the methyl orange end point. For this reason mineral acidity is also called methyl orange acidity. Titration of a sample to the phenolphthalein end point of pH 8.3 measures both mineral acidity plus acidity due to weak acids. This total acidity is also termed phenolphthalein acidity. jf reliable results are to be obtained,...

Binary Mixtures

Binary mixtures of miscible liquids such as Water and ethanol are of interest because of the differences in vapor pressure that they exhibit and the influence that vapor pressure has upon their separation by distillation. All mixtures fall into one of three classes, and their properties are considerably different. Class 1 includes all mixtures with total vapor pressure, regardless of the composition of the mixture, that is always less than that of the most volatile component and always more...

General Considerations

The chemical oxygen demand (COD) test is widely used as a means of measuring the organic strength of domestic and industrial wastes. This test allows measurement of a waste in terms of the total quantity of oxygen required for oxidation to carbon dioxide and water in accordance with Eq. (23.1). It is based upon the fact that all organic compounds, with a few exceptions, can be oxidized by the action of strong oxidizing agents under acid conditions. The amino nitrogen (with an oxidation number...

V V

Important derivatives of purine are adenine and guanine, and of pyrimidine are cy-tosine, uracil, and thymine. These compounds or bases form the major components of nucleic acids, which carry the genetic information for all life (see Sec. 6.14). In addition, they are components of key biological molecules such as ATP, the primary carrier of chemical energy in all cells, and coenzyme A, which is necessary for fatty acid degradation. Indole and skatole are examples of heterocyclic compounds that...

Environmental Significance Of Nitrogen Species

While nitrogen is seen to be an essential component of all living things, excessive concentrations of certain nitrogen species in some compartments of the environment can lead to significant environmental problems. This is true of some nitrogen species in the atmosphere as well as in terrestrial and aquatic environments. Atmospheric Concerns with Nitrogen Species The three major environmental problems associated with nitrogen species in the atmosphere are photochemical smog, global warming, and...

Preparation Of 100 N AND 0020 N NaOh Solutions

Standard solutions of sodium hydroxide are used to measure carbon dioxide and acidity. The equivalent weight of carbon dioxide when reacting with sodium hy- I droxide, to pH 8.3 or the phenolphthalein end point, is 44, as may be calculated from the equation COa + Na+ + OH -> Na+ + HCOj (15.1) Therefore, N 44 or 0.0227 N solutions of NaOH are best suited for determination of carbon dioxide. Mineral acidity is always expressed in terms of calcium carbonate, which has an equivalent weight of 50,...

Water and Wastewater Analysis 399

9.1 Importance of Quantitative Measurements 401 9.2 Character of Environmental Engineering and Science Problems 402 9.3 Standard Methods of Analysis 402 9.4 Scope of a Course in Analysis of Environmental Samples 402 9.6 Other Items 408 Problems 408 Statistical Analysis of Analytical Data 410 10.2 Rounding Numerical Data 411 10.4 Distribution of Experimental Data 416 10.8 Lognormal Distribution 433 10.10 Quality Assurance and Quality Control 446 11.2 The Analytical Balance 455 11.6 Physical...

Effect Of Radiation On Humans

Radiation effects on humans are classified as somatic or genetic. Somatic effects are those that cause damage to the individual and include anemia, fatigue, loss of hair, cataracts, skin rash, and cancer. Genetic effects include inheritable changes ) resulting from mutations in reproductive cells. It is widely held that even small dosages of radiation can have some adverse effects, genetic effects being of most concern. Humans are exposed to varying levels of natural radiation, especially from...

Application Of Fluoride Data

Because of the public health significance of fluoride in water supplies intended for human use, determination of fluoride has become important. In situations where fluoride is added to provide an optimum level for the control of dental caries, it is necessary to know the amount of natural fluoride present so that proper amounts of supplemental fluoride can be added. Wherever supplementation is practiced, it is necessary to maintain surveillance on the finished water to be sure that proper...

Thermodynamics

Thermodynamics is the study of energy changes accompanying physical and chemical processes. The energy changes associated with chemical reactions are of considerable importance and will be briefly discussed to indicate the relationships of most interest in environmental engineering and science. First, it is necessary to review the relationship between heat and work. Heat and work are related forms of energy. Heat energy can be converted into work,-and work can be converted into heat energy....

Chemical Oxygen Demand By Dichromate

Potassium dichromate is a relatively cheap compound that can be obtained in a high state of purity. The analytical-reagent grade, after drying at 103 C, can be used to prepare solutions of an exact normality by direct weighing and dilution to the proper volume. The dichromate ion, is a very potent oxidizing agent in solutions that are strongly acidic. The reaction involved in the usual case, where organic nitrogen is all in a reduced state (oxidation number of -3), may be represented in a...

Methods Of Chlorine Residual Determination

It was not until about 1940 that the difference in disinfecting power of chloramine and free chlorine residuals was demonstrated. Prior to that time no attempt had been made to develop analytical procedures for differentiation. Therefore, methods for measuring chlorine residuals may be classed into old methods that measure total chlorine and new methods that allow measurement of free and combined forms. CHAPTER 20 Residual Chlorine and Chlorine Demand AH common methods of measuring chlorine...

Methods Of Determination

There are several Standard Methods procedures for measurement of chloride. Among these are a potentiometric procedure (Sec. 12.3) using silver nitrate as a ' tjtrant to complex chloride with silver and employing a silver-silver chloride electrode system to detect the end point, and ion chromatography (Sec. 12.4), which is useful for determining concentrations of several common anions in one analysis. These instrumental methods require somewhat expensive equipment. Two other procedures that are...

Ch cr cr

p-Xylene It exists in three isomeric forms ortho-xylene, meta-xylene, and paxa-xylene. All i are isomeric with ethylbenzene in that they have the same general formula, CgH10. j Together with benzene, these compounds are commonly referred to as the BTEX j group. The benzene-series hydrocarbons are used extensively as solvents and in chem- i ical synthesis, and are common constituents of petroleum products (e.g., gasoline), j Although they are relatively insoluble in water, wastewaters and...

Logarithmic Diagram Of Concentration Of Weak Acid

Note that in mass balance, charge balance, and proton condition relationships, molar concentrations and not activities are required. - V- . The ionic strength must now be calculated so that activity corrections can be made. Since HAc is a weak acid, its ionization can be ignored ( Ac- - 0) and we can assume that the ionic strength is due entirely to the added NaCl. ,V P- Sc.z 0.5 0.01(1)2 + O.Ol(-l)2 0.01 M Using the Guntelberg approximation Eq. (4.2) . log 7 -0.5Z2 V5 L -0.0455Z2 ' 1 + VOOl...

Basic Concepts from Equilibrium Chemistry

A knowledge of equilibrium chemistry has become increasingly important for determining quantitatively the relationships between the various constituents in natural and contaminated waters, and for understanding the effect of alterations in the water on the various chemical species present. This is a matter of growing importance because of the use of physical-chemical methods for treating wastewaters and sanitary-landfill leachates and the need to understand the fate and transport of both...

Methods Of Expressing Alkalinity

Alkalinity measurements are made on a wide variety of materials. These range from relatively pure waters through polluted waters, such as municipal and industrial wastewaters, to digesting sludges. The methods of expressing alkalinity values vary considerably therefore, it is necessary to explain the methods in some detail and to indicate the areas where the various methods are employed. Phenolphthalein and Total Alkalinity Inspection of the titration curves for a strong base (hydroxide...

K um K kb[ ORT

Care must be taken to ensure that the units used in these rate expressions are The concept of half-life is often used to describe the persistence of an organic in the environment. Half-life (i1 2) was defined in Sec. 3.10 as 0.693Ik, where k is a grst-orderrate coefficient. With hydrolysis, k is represented by kh or kh N , Hydrolysis reactions may be quite slow (half-lives of years) or quite rapid (half-lives of seconds) depending on the organic and the environmental conditions. The following...

Discrepancy Between L0 Values And Theoretical Oxygen Demand Values

The ultimate BOD, or L0, value of organic substances is often considered to be equal to the theoretical oxygen demand as calculated from the chemical equation involved see Eq. (23.1) . For example, oxidation of glucose to carbon dioxide and water requires 192 g of oxygen per mole or 1.065 mg of oxygen per milligram of glucose. c6h1206 + 602 6c02 + 6h20 (23.15) A great deal of BOD work has been done with glucose solutions in a concentration of 300 mg L. Such a solution has a theoretical oxygen...

Chapter

Basic Concepts from Organic Chemistry 212 5.1 Introduction 212 Aliphatic Compounds 5.8 Alkyl Halides and Other Halogenated Aliphatic Compounds 237 5.9 Simple Compounds Containing Nitrogen 242 5.10 Cyclic Aliphatic Compounds 245 5.11 Mercaptans or Thioalcohols 245 Aromatic Compounds 5.15 Alcohols, Aldehydes, Ketones, and Acids 254 5.16 Simple Compounds Containing Nitrogen 256 Heterocyclic Compounds 5.17 Heterocyclic Compounds 258 The Common Foods and Related Compounds 5.22 Proteins and Amino...

Volumetric Analysis

Early methods of volumetric analysis employed separate measurement of carbon dioxide and oxygen, followed by a slow simultaneous combustion of hydrogen and methane. The analysis was completed by measuring the amount of carbon dioxide produced during the combustion of the methane and then employing a knowledge of Gay-Lussac's law of combining volumes (Sec. 2.9) to determine the amounts of methane and hydrogen present in the mixture. In the past an apparatus was sometimes used that employed a...

The Safe Drinking Water

The critical nature of the water supply problem brought congressional action resulting in Public Law 93-523, known as the Safe Drinking Water Act (SDWA), which was signed into law in 1974, It then became incumbent upon the newly formed Environmental Protection Agency (EPA) to interpret the law and establish Drinking Water Standards that apply to all public water systems in the United States, not just those that supply common carriers, as did the U.S. Public Health Standards. The SDWA was...

Types Of Hardness

In addition to total hardness, it is desirable and sometimes necessary to know the types of hardness present. Hardness is classified in two ways (1) with respect to the metallic ion and (2) with respect to the anions associated with the metallic ions. Calcium and magnesium cause by far the greatest portion of the hardness occurring in natural waters. In some considerations it is important to know the amounts of calcium and magnesium hardness in water. For example, it is necessary to know the...

Computer Methods For Solving Equilibrium Problems

The chemical equilibrium problems presented in this chapter are relatively simple ones involving only a few species and equilibrium expressions. They have been solved using equilibrium constants, mass balances, charge balances, and sometimes proton conditions, and spreadsheets or by making simplifying assumptions and generating quadratic equations or by drawing log concentration diagrams. However, for more complex problems where many species are involved (say more than 15 to 20), where several...

Chemical Kinetics

Chemical kinetics is concerned with the speed or velocity of reactions. Many reactions have rates that at a given temperature are proportional to the concentration of one, two, or more of the reactants raised to a small integral power. For example, if a reaction is considered in which A, B, and C are possible reactants, then the rate equations that express the concentration dependence of the reaction rate may take one of the following forms, among others Rate kC2a or kCaCb second order Rate kC...

Significance Of Carbon Dioxide And Mineral Acidity

Acidity is of little concern from a sanitary or public health viewpoint. Carbon dioxide is present in malt and carbonated beverages in concentrations greatly in excess of any concentrations known in natural waters, and no deleterious effects due to the carbon dioxide have been recognized. Waters that contain mineral acidity are so unpalatable that problems related to human consumption are nonexistent. Acid waters are of concern because of their corrosive characteristics and the expense involved...

Methods Of Determining Volatile Acids

Two methods of deteimining volatile acids are currently described in Standard Methods. One uses column-partition chromatography, and the other involves distillation. Several laboratories today also use gas chromatography or ion chromatography (Sec. 12.4) for the measurement of the concentration of individual volatile acids, although these procedures are not yet considered as standard. They may be in the future as we leam more about the significance of individual volatile acids in the control of...

Significance Of Chloride

Chloride in reasonable concentrations is not harmful to humans. At concentrations above 250 mg L it gives a salty taste to water, which is objectionable to many people. For this reason a secondary standard of 250 mg L for chloride in drinking water has been set by the U.S. EPA, the same value contained in the WHO guidelines. In many areas of the world where water supplies are scarce, sources containing as much as 2000 mg L are used for domestic purposes without the development of adverse...

Oxidationreduction Reactions

Oxidation-reduction reactions are among the most important with which environmental engineers and scientists deal. Many reactions of interest in wastewater treatment such as organic oxidation and methane fermentation, nitrification, and denitri-fication are of this type and are mediated by bacteria. Oxidation-reduction reactions are important in the solubilization and precipitation of iron and manganese. Oxidants such as chlorine and ozone are added to water and wastewater to bring about...

Methods Of Determining Fluoride

There are four standard methods for determination of fluoride at the present time the electrode method, two colorimetric procedures, and ion chromatography. The electrode method is the simplest but does require use of an expanded-scale pH meter and a special electrode. The principles behind and limitations of the electrode method are described under Crystalline Membrane Electrode in Sec. 12.3. The ion chromatographic technique, described in Sec. 12.4, permits analysis for fluoride and several...

Chcl2ch2br Name

Chapter 5 Basic Concepts from Organic Chemistry ch2 ch ch ch3 ch3ch2ch5cooh ch3 A contaminated groundwater contains 50 (j,g L chlorobenzene, 25 Ag L dichloromethane, and 85 xg L ethylbenzene. Using the simplified equilibrium model developed in Sec. 5.34, estimate the air-to-water ratio required to reduce the concentration of each of these compounds below 5 ig L, Assume a temperature of 25 c. If you were to design a stripping tower to remove these contaminants, would you expect your design...

Cause And Source Of Hardness

Hardness is caused by multivalent metallic cations. Such ions are capable of reacting with soap to form precipitates and with certain anions present in the water to form scale. The principal hardness-causing cations are the divalent calcium, magnesium, strontium, ferrous iron, and manganous ions. These cations, plus the most important anions with which they are associated, are shown in Table 19.1 in the order of their relative abundance in natural waters. Aluminum and ferric ions are sometimes...

Colloidal Dispersions In Liquids

Colloidal dispersions of solids, liquids, and gases in liquids are commonly encountered in environmental engineering and science. The nomenclature and behavior of each type differ somewhat consequently, discussions of each will be given. Colloidal dispersion's of solids in liquids are generally of two types, those that bind j strongly with the liquid and those that do not. Dispersions binding strongly with the I liquid are generally more stable and difficult to separate from the liquid than...

Method Of Measuring

The BOD test is based upon determinations of dissolved oxygen consequently, the accuracy of the results is influenced greatly by the care given to its measurement. BOD may be measured directly in a few samples, but in general, a dilution procedure is required. For samples with 5-day BOD less than 7 mg L, it is not necessary to dilute them, provided that they are aerated to bring the dissolved-oxygen level nearly to saturation at the start of the test. Many river waters fall into this category....

Method Of Determining Alkalinity

Alkalinity Titration Curve

Alkalinity is measured volumetrically by titration with N 50 or 0.020 N H2S04 and is reported in terms of equivalent CaC03. For samples whose initial pH is above 8.3, the titration is made in two steps. In the first step the titration is conducted until the pH is lowered to 8.3, the point at which phenolphthalein indicator turns from pink to colorless. The second phase of the titration is conducted until the pH is lowered to about 4.5, corresponding to the bromcresol green end point. When the...