Soil texture is a classification instrument used both in the field and laboratory to determine soil classes based on their physical texture. Soil texture can be determined using qualitative methods such as texture by feel, quantitative methods such as the hydrometer method. Soil texture has agricultural applications such as determining crop suitability and to predict the response of the soil to environmental and management conditions such as drought or calcium requirements. Soil texture focuses on the particles that are less than two millimeters in diameter which include sand and clay; the USDA soil taxonomy and WRB soil classification systems use 12 textural classes whereas the UK-ADAS system uses 11. These classifications are based on the percentages of sand and clay in the soil.. In the United States, twelve major soil texture classifications are defined by the USDA; the twelve classifications are sand, loamy sand, sandy loam, silt loam, sandy clay loam, clay loam, silty clay loam, sandy clay, silty clay, clay.
Soil textures are classified by the fractions of each soil separate present in a soil. Classifications are named for the primary constituent particle size or a combination of the most abundant particles sizes, e.g. "sandy clay" or "silty clay". A fourth term, loam, is used to describe equal properties of sand and clay in a soil sample, lends to the naming of more classifications, e.g. "clay loam" or "silt loam". Determining soil texture is aided with the use of a soil texture triangle. An example of a soil triangle is found on the right side of the page. One side of the triangle represents percent sand, the second side represents percent clay, the third side represents percent silt. If you know the percentages of sand and silt in your soil sample, the triangle can be used to determine which of the twelve soil types you have. To do this, find your percentage of sand along the bottom of the triangle. Follow the slanted line up to the left until you reach your percentage of clay. Where that point is will tell you what soil type you have.
For example, if your soil is 70 percent sand and 10 percent clay your soil is classified as a sandy loam. The same method can be used starting on any side of the soil triangle. If the texture by feel method was used to determine which type of soil you had, the triangle can provide a rough estimate on the percentages of sand and clay in your soil. Chemical and physical properties of a soil are related to texture. Particle size and distribution will affect a soil's capacity for nutrients. Fine textured soils have a higher capacity for water retention, whereas sandy soils contain large pore spaces that allow leaching. Soil separates are specific ranges of particle sizes; the smallest particles are clay particles and are classified as having diameters of less than 0.002 mm. Clay particles are plate-shaped instead of spherical, allowing for an increased specific surface area; the next smallest particles are silt have diameters between 0.002 mm and 0.05 mm. The largest particles are larger than 0.05 mm in diameter.
Furthermore, large sand particles can be described as coarse, intermediate as medium, the smaller as fine. Other countries have their own particle size classifications. Hand analysis is a simple and effective means to assess and classify a soil's physical condition. Executed, the procedure allows for rapid and frequent assessment of soil characteristics with little or no equipment, it is thus an useful tool for identifying spatial variation both within and between fields as well as identifying progressive changes and boundaries between soil map units. Texture by feel is a qualitative method, it does not provide exact values of sand and clay. Although qualitative, the texture by feel flowchart can be an accurate way for a scientist or interested individual to analyze the relative proportions of sand and clay; the texture by feel method involves making a ribbon. A ribbon can be made by taking a ball of soil and pushing the soil between your thumb and forefinger, squeezing it upward into a ribbon.
Allow the ribbon to emerge and extend over the forefinger, breaking from its own weight. Measuring the length of the ribbon can help determine the amount of clay in the sample. After making a ribbon, excessively wet a small pinch of soil in the palm of your hand and rub in with your forefinger to determine the amount of sand in the sample. Soils that have a high percentage of sand, such as sandy loam, or sandy clay, have a gritty texture. Soils that have a high percentage of silt, such as silty loam or silty clay, feel smooth. Soils that have a high percentage of clay, such as clay loam, have a sticky feel. Although the texture by feel method takes practice, it is a useful way to determine soil texture in the field; the hydrometer method of determining soil texture is a quantitative measurement providing estimates of the percent sand and silt in the soil. The hydrometer method was developed in 1927 and is still used today; this method requires a chemical compound, sodium hexametaphsophate, which acts as a dispersing agent to separate soil aggregates.
The soil is mixed with the sodium hexametaphosphate solution on an orbital shaker overnight. The solution is filled with water; the soil solution is mixed with a metal plunger to disperse the soil particles. The soil particles sink to the bottom. Sand particles are the sink to the bottom of the cylinder first. Silt particles are the medium-sized (0.05
PubChem is a database of chemical molecules and their activities against biological assays. The system is maintained by the National Center for Biotechnology Information, a component of the National Library of Medicine, part of the United States National Institutes of Health. PubChem can be accessed for free through a web user interface. Millions of compound structures and descriptive datasets can be downloaded via FTP. PubChem contains substance descriptions and small molecules with fewer than 1000 atoms and 1000 bonds. More than 80 database vendors contribute to the growing PubChem database. PubChem consists of three dynamically growing primary databases; as of 1 November 2017: Compounds, 93.9 million entries, contains pure and characterized chemical compounds. Substances, 236 million entries, contains mixtures, extracts and uncharacterized substances. BioAssay, bioactivity results from 1.25 million high-throughput screening programs with several million values. Searching the databases is possible for a broad range of properties including chemical structure, name fragments, chemical formula, molecular weight, XLogP, hydrogen bond donor and acceptor count.
PubChem contains its own online molecule editor with SMILES/SMARTS and InChI support that allows the import and export of all common chemical file formats to search for structures and fragments. Each hit provides information about synonyms, chemical properties, chemical structure including SMILES and InChI strings and links to structurally related compounds and other NCBI databases like PubMed. In the text search form the database fields can be searched by adding the field name in square brackets to the search term. A numeric range is represented by two numbers separated by a colon; the search terms and field names are case-insensitive. Parentheses and the logical operators AND, OR, NOT can be used. AND is assumed. Example: 0:500 0:5 0:10 -5:5 PubChem was released in 2004; the American Chemical Society has raised concerns about the publicly supported PubChem database, since it appears to directly compete with their existing Chemical Abstracts Service. They have a strong interest in the issue since the Chemical Abstracts Service generates a large percentage of the society's revenue.
To advocate their position against the PubChem database, ACS has lobbied the US Congress. Soon after PubChem's creation, the American Chemical Society lobbied U. S. Congress to restrict the operation of PubChem, which they asserted competes with their Chemical Abstracts Service. Chemical database CAS Common Chemistry - run by the American Chemical Society Comparative Toxicogenomics Database - run by North Carolina State University ChEMBL - run by European Bioinformatics Institute ChemSpider - run by UK's Royal Society of Chemistry DrugBank - run by the University of Alberta IUPAC - run by Swiss based International Union of Pure and Applied Chemistry Moltable - run by India's National Chemical Laboratory PubChem - run by the National Institute of Health, USA BindingDB - run by the University of California, San Diego SCRIPDB - run by the University of Toronto, Canada National Center for Biotechnology Information - run by the National Institute of Health, USA Entrez - run by the National Institute of Health, USA GenBank - run by the National Institute of Health, USA Official website
Sodium phosphate is a generic term for a variety of salts of sodium and phosphate. Phosphate forms families or condensed anions including di-, tri-, tetra-, polyphosphates. Most of these salts are known in both hydrated forms; the hydrates are more common. Sodium phosphates have many applications for water treatment. For example, sodium phosphates are used as emulsifiers, thickening agents, leavening agents for baked goods, they are used to control pH of processed foods. They are used in medicine for constipation and to prepare the bowel for medical procedures. Moreover, they are used in detergents for softening water, as an efficient anti rust solution. Sodium phosphates are popular in commerce in part because they are inexpensive and because they are nontoxic at normal levels of consumption. However, oral sodium phosphates when taken at high doses for bowel preparation for colonoscopy may in some individuals carry a risk of kidney injury under the form of phosphate nephropathy. There are several oral phosphate formulations.
Oral phosphate prep drugs have been withdrawn in the United States, although evidence of causality is equivocal. Since safe and effective replacements for phosphate purgatives are available, several medical authorities have recommended general disuse of oral phosphates. Three families of sodium monophosphates are common, those derived from orthophosphate, hydrogen phosphate, dihydrogenphosphate; some of the most well known salts are shown in the table. In addition to these phosphates, sodium forms a number of useful salts with pyrophosphates and high polymers. Of these salts, those of the diphosphates are common commercially. Beyond the diphosphates, sodium salts are known triphosphates, e.g. sodium triphosphate and tetraphospates. The cyclic polyphosphates, called metaphosphates, include the trimer sodium trimetaphosphate and the tetramer, Na3P3O9 and Na4P4O12, respectively. Polymeric sodium phosphates are formed upon heating mixtures of NaH2PO4 and Na2HPO4, which induces a condensation reaction.
The specific polyphosphate generated depends on the details of the annealling. One derivative is the glassy Graham's salt. Crystalline high molecular weight polyphosphates include Maddrell's salt; these species have the formula n2 where n can be as great as 2000. In terms of their structures, these polymers consist of PO3− "monomers", with the chains are terminated by protonated phosphates. Bell, Russel N, "Sodium Aluminum Phosphate Cheese Emulsifying Agent", US Patent 3726960 Lien, YH, "Is bowel preparation before colonoscopy a risky business for the kidney?", Nature Clinical Practice Nephrology, 4: 606–14, doi:10.1038/ncpneph0939, PMID 18797448
Simplified molecular-input line-entry system
The simplified molecular-input line-entry system is a specification in the form of a line notation for describing the structure of chemical species using short ASCII strings. SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules; the original SMILES specification was initiated in the 1980s. It has since been extended. In 2007, an open standard called. Other linear notations include the Wiswesser line notation, ROSDAL, SYBYL Line Notation; the original SMILES specification was initiated by David Weininger at the USEPA Mid-Continent Ecology Division Laboratory in Duluth in the 1980s. Acknowledged for their parts in the early development were "Gilman Veith and Rose Russo and Albert Leo and Corwin Hansch for supporting the work, Arthur Weininger and Jeremy Scofield for assistance in programming the system." The Environmental Protection Agency funded the initial project to develop SMILES. It has since been modified and extended by others, most notably by Daylight Chemical Information Systems.
In 2007, an open standard called "OpenSMILES" was developed by the Blue Obelisk open-source chemistry community. Other'linear' notations include the Wiswesser Line Notation, ROSDAL and SLN. In July 2006, the IUPAC introduced the InChI as a standard for formula representation. SMILES is considered to have the advantage of being more human-readable than InChI; the term SMILES refers to a line notation for encoding molecular structures and specific instances should be called SMILES strings. However, the term SMILES is commonly used to refer to both a single SMILES string and a number of SMILES strings; the terms "canonical" and "isomeric" can lead to some confusion when applied to SMILES. The terms are not mutually exclusive. A number of valid SMILES strings can be written for a molecule. For example, CCO, OCC and CC all specify the structure of ethanol. Algorithms have been developed to generate the same SMILES string for a given molecule; this SMILES is unique for each structure, although dependent on the canonicalization algorithm used to generate it, is termed the canonical SMILES.
These algorithms first convert the SMILES to an internal representation of the molecular structure. Various algorithms for generating canonical SMILES have been developed and include those by Daylight Chemical Information Systems, OpenEye Scientific Software, MEDIT, Chemical Computing Group, MolSoft LLC, the Chemistry Development Kit. A common application of canonical SMILES is indexing and ensuring uniqueness of molecules in a database; the original paper that described the CANGEN algorithm claimed to generate unique SMILES strings for graphs representing molecules, but the algorithm fails for a number of simple cases and cannot be considered a correct method for representing a graph canonically. There is no systematic comparison across commercial software to test if such flaws exist in those packages. SMILES notation allows the specification of configuration at tetrahedral centers, double bond geometry; these are structural features that cannot be specified by connectivity alone and SMILES which encode this information are termed isomeric SMILES.
A notable feature of these rules is. The term isomeric SMILES is applied to SMILES in which isotopes are specified. In terms of a graph-based computational procedure, SMILES is a string obtained by printing the symbol nodes encountered in a depth-first tree traversal of a chemical graph; the chemical graph is first trimmed to remove hydrogen atoms and cycles are broken to turn it into a spanning tree. Where cycles have been broken, numeric suffix labels are included to indicate the connected nodes. Parentheses are used to indicate points of branching on the tree; the resultant SMILES form depends on the choices: of the bonds chosen to break cycles, of the starting atom used for the depth-first traversal, of the order in which branches are listed when encountered. Atoms are represented by the standard abbreviation of the chemical elements, in square brackets, such as for gold. Brackets may be omitted in the common case of atoms which: are in the "organic subset" of B, C, N, O, P, S, F, Cl, Br, or I, have no formal charge, have the number of hydrogens attached implied by the SMILES valence model, are the normal isotopes, are not chiral centers.
All other elements must be enclosed in brackets, have charges and hydrogens shown explicitly. For instance, the SMILES for water may be written as either O or. Hydrogen may be written as a separate atom; when brackets are used, the symbol H is added if the atom in brackets is bonded to one or more hydrogen, followed by the number of hydrogen atoms if greater than 1 by the sign + for a positive charge or by - for a negative charge. For example, for ammonium. If there is more than one charge, it is written as digit.
Safety data sheet
A safety data sheet, material safety data sheet, or product safety data sheet is a document that lists information relating to occupational safety and health for the use of various substances and products. SDSs are a used system for cataloging information on chemicals, chemical compounds, chemical mixtures. SDS information may include instructions for the safe use and potential hazards associated with a particular material or product, along with spill-handling procedures. SDS formats can vary from source to source within a country depending on national requirements. A SDS for a substance is not intended for use by the general consumer, focusing instead on the hazards of working with the material in an occupational setting. There is a duty to properly label substances on the basis of physico-chemical, health or environmental risk. Labels can include hazard symbols such as the European Union standard symbols; the same product can have different formulations in different countries. The formulation and hazard of a product using a generic name may vary between manufacturers in the same country.
The Globally Harmonized System of Classification and Labelling of Chemicals contains a standard specification for safety data sheets. The SDS follows a 16 section format, internationally agreed and for substances the SDS should be followed with an Annex which contains the exposure scenarios of this particular substance; the 16 sections are: SECTION 1: Identification of the substance/mixture and of the company/undertaking 1.1. Product identifier 1.2. Relevant identified uses of the substance or mixture and uses advised against 1.3. Details of the supplier of the safety data sheet 1.4. Emergency telephone number SECTION 2: Hazards identification 2.1. Classification of the substance or mixture 2.2. Label elements 2.3. Other hazards SECTION 3: Composition/information on ingredients 3.1. Substances 3.2. Mixtures SECTION 4: First aid measures 4.1. Description of first aid measures 4.2. Most important symptoms and effects, both acute and delayed 4.3. Indication of any immediate medical attention and special treatment needed SECTION 5: Firefighting measures 5.1.
Extinguishing media 5.2. Special hazards arising from the substance or mixture 5.3. Advice for firefighters SECTION 6: Accidental release measure 6.1. Personal precautions, protective equipment and emergency procedures 6.2. Environmental precautions 6.3. Methods and material for containment and cleaning up 6.4. Reference to other sections SECTION 7: Handling and storage 7.1. Precautions for safe handling 7.2. Conditions for safe storage, including any incompatibilities 7.3. Specific end use SECTION 8: Exposure controls/personal protection 8.1. Control parameters 8.2. Exposure controls SECTION 9: Physical and chemical properties 9.1. Information on basic physical and chemical properties 9.2. Other information SECTION 10: Stability and reactivity 10.1. Reactivity 10.2. Chemical stability 10.3. Possibility of hazardous reactions 10.4. Conditions to avoid 10.5. Incompatible materials 10.6. Hazardous decomposition products SECTION 11: Toxicological information 11.1. Information on toxicological effects SECTION 12: Ecological information 12.1.
Toxicity 12.2. Persistence and degradability 12.3. Bioaccumulative potential 12.4. Mobility in soil 12.5. Results of PBT and vPvB assessment 12.6. Other adverse effects SECTION 13: Disposal considerations 13.1. Waste treatment methods SECTION 14: Transport information 14.1. UN number 14.2. UN proper shipping name 14.3. Transport hazard class 14.4. Packing group 14.5. Environmental hazards 14.6. Special precautions for user 14.7. Transport in bulk according to Annex II of MARPOL73/78 and the IBC Code SECTION 15: Regulatory information 15.1. Safety and environmental regulations/legislation specific for the substance or mixture 15.2. Chemical safety assessment SECTION 16: Other information 16.2. Date of the latest revision of the SDS In Canada, the program known as the Workplace Hazardous Materials Information System establishes the requirements for SDSs in workplaces and is administered federally by Health Canada under the Hazardous Products Act, Part II, the Controlled Products Regulations. Safety data sheets have been made an integral part of the system of Regulation No 1907/2006.
The original requirements of REACH for SDSs have been further adapted to take into account the rules for safety data sheets of the Global Harmonised System and the implementation of other elements of the GHS into EU legislation that were introduced by Regulation No 1272/2008 via an update to Annex II of REACH. The SDS must be supplied in an official language of the Member State where the substance or mixture is placed on the market, unless the Member State concerned provide otherwise; the European Chemicals Agency has published a guidance document on the compilation of safety data sheets. The German Federal Water Management Act requires that substances be evaluated for negative influence on the physical, chemical or biological characteristics of water; these are classified into numeric water hazard classes. WGK nwg: Non-water polluting substance WGK 1: Slightly water polluting substance WGK 2: Water polluting substance WGK 3: Highly water polluting substance This section contributes to a better understanding of the regulations governing SDS within the South African framework.
As regulations may change, it is the responsibility of the reader to verify the validity of the regulations mentioned in text. As globalisation increased and countries engaged in cross-border trade, the quantity of hazardous material crossing international borders a
Sodium carbonate, Na2CO3, is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, water-soluble salts. All forms have a alkaline taste and give moderately alkaline solutions in water, it was extracted from the ashes of plants growing in sodium-rich soils. Because the ashes of these sodium-rich plants were noticeably different from ashes of wood, sodium carbonate became known as "soda ash", it is produced in large quantities from sodium limestone by the Solvay process. Sodium carbonate is obtained as three different hydrates and as the anhydrous salt: sodium carbonate decahydrate, Na2CO3·10H2O, which effloresces to form the monohydrate. Sodium carbonate heptahydrate, Na2CO3·7H2O. Sodium carbonate monohydrate, Na2CO3·H2O. Known as crystal carbonate. Anhydrous sodium carbonate known as calcined soda, is formed by heating the hydrates, it is formed when sodium hydrogen carbonate is heated e.g. in the final step of the Solvay process. The decahydrate is formed from water solutions crystallizing in the temperature range -2.1 to +32.0 C, the heptahydrate in the narrow range 32.0 to 35.4 C and above this temperature the monohydrate forms.
In dry air the decahydrate and heptahydrate lose water to give the monohydrate. Other hydrates have been reported. In terms of its largest applications, sodium carbonate is used in the manufacture of glass, rayon and detergents. Sodium carbonate serves as a flux for silica, lowering the melting point of the mixture to something achievable without special materials; this "soda glass" is mildly water-soluble, so some calcium carbonate is added to the melt mixture to make the glass produced insoluble. Bottle and window glass is made by melting such mixtures of sodium carbonate, calcium carbonate, silica sand; when these materials are heated, the carbonates release carbon dioxide. In this way, sodium carbonate is a source of sodium oxide. Soda lime glass has been the most common form of glass for centuries. Sodium carbonate is used to soften water by removing Mg2+ and Ca2+; these ions form insoluble solid precipitates upon treatment with carbonate ions: Ca2+ + CO32- → CaCO3Sodium carbonate is an inexpensive and water-soluble source of carbonate ions.
Sodium carbonate is a food additive used as an acidity regulator, anticaking agent, raising agent, stabilizer. It is one of the components of kansui, a solution of alkaline salts used to give ramen noodles their characteristic flavor and texture, it is used in the production of snus to stabilize the pH of the final product. Sodium carbonate is used in the production of sherbet powder; the cooling and fizzing sensation results from the endothermic reaction between sodium carbonate and a weak acid citric acid, releasing carbon dioxide gas, which occurs when the sherbet is moistened by saliva. In China, it is used to replace lye-water in the crust of traditional Cantonese moon cakes, in many other Chinese steamed buns and noodles. In cooking, it is sometimes used in place of sodium hydroxide for lyeing with German pretzels and lye rolls; these dishes are treated with a solution of an alkaline substance to change the pH of the surface of the food and improve browning. Sodium carbonate is used as a strong base in various fields.
As a common alkali, it is preferred in many chemical processes because it is cheaper than NaOH and far safer to handle. Its mildness recommends its use in domestic applications. For example, it is used as a pH regulator to maintain stable alkaline conditions necessary for the action of the majority of photographic film developing agents. For example, it is a common additive in swimming pools and aquarium water to maintain a desired pH and carbonate hardness. In dyeing with fiber-reactive dyes, sodium carbonate is used to ensure proper chemical bonding of the dye with cellulose fibers before dyeing, mixed with the dye, or after dyeing. Sodium bicarbonate or baking soda a component in fire extinguishers, is generated from sodium carbonate. Although NaHCO3 is itself an intermediate product of the Solvay process, the heating needed to remove the ammonia that contaminates it decomposes some NaHCO3, making it more economic to react finished Na2CO3 with CO2: Na2CO3 + CO2 + H2O → 2NaHCO3In a related reaction, sodium carbonate is used to make sodium bisulphite, used for the "sulfite" method of separating lignin from cellulose.
This reaction is exploited for removing sulphur dioxide from flue gases in power stations: Na2CO3 + SO2 + H2O → NaHCO3 + NaHSO3This application has become more common where stations have to meet stringent emission controls. Sodium carbonate is used by the cotton industry to neutralize the sulfuric acid needed for acid delinting of fuzzy cottonseed. Sodium carbonate is used by the brick industry as a wetting agent to reduce the amount of water needed to extrude the clay. In casting, it is referred to as "bonding agent" and is used to allow wet alginate to adhere to gelled alginate. Sodium carbonate is used in toothpastes, where it acts as a foaming agent and an abrasive, to temporarily increase mouth pH; the integral enthalpy of solution of sodium carbonate is −28.1 kJ/mol for a 10% w/w aqueous solution. The Mohs hardness of sodium carbonate monohydrate is 1.3. Sodium carbonate is soluble in water, can occur nat