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Phenol Coefficient
The Phenol coefficient, is now largely of historical interest, although the principles upon which it is based are still used. It is a measure of the bactericidal activity of a chemical compound in relation to phenol. When listed numerically, the figure expressing the disinfecting power of a substance by relating it to the disinfecting power of phenol may be a function of the standardized test performed. For example, the Rideal–Walker method, introduced in 1903 gives a Rideal–Walker coefficient and the U.S. Department of Agriculture method gives a U.S. Department of Agriculture coefficient. To calculate phenol coefficient, the concentration of phenol at which the compound kills the test organism in 10 minutes, but not in 5 minutes, is divided by the concentration of the test compound that kills the organism under the same conditions (or, probably more common, dividing the dilution factor at which the tested substance shows activity by the dilution factor at which phenol sh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bactericidal
A bactericide or bacteriocide, sometimes abbreviated Bcidal, is a substance which kills bacteria. Bactericides are disinfectants, antiseptics, or antibiotics. However, material surfaces can also have bactericidal properties based solely on their physical surface structure, as for example biomaterials like insect wings. Disinfectants The most used disinfectants are those applying *active chlorine (i.e., hypochlorites, chloramines, dichloroisocyanurate and trichloroisocyanurate, wet chlorine, chlorine dioxide, etc.), *active oxygen (peroxides, such as peracetic acid, potassium persulfate, sodium perborate, sodium percarbonate, and urea perhydrate), * iodine ( povidone-iodine, Lugol's solution, iodine tincture, iodinated nonionic surfactants), *concentrated alcohols (mainly ethanol, 1-propanol, called also n-propanol and 2-propanol, called isopropanol and mixtures thereof; further, 2-phenoxyethanol and 1- and 2-phenoxypropanols are used), * phenolic substances (such a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phenol
Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it requires careful handling because it can cause chemical burns. Phenol was first extracted from coal tar, but today is produced on a large scale (about 7 billion kg/year) from petroleum-derived feedstocks. It is an important industrial commodity as a precursor to many materials and useful compounds. It is primarily used to synthesize plastics and related materials. Phenol and its chemical derivatives are essential for production of polycarbonates, epoxies, Bakelite, nylon, detergents, herbicides such as phenoxy herbicides, and numerous pharmaceutical drugs. Properties Phenol is an organic compound appreciably soluble in water, with about 84.2 g dissolving in 1000 mL (0.895 M). Homogeneous mixtures of phenol and water ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disinfection
A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than sterilization, which is an extreme physical or chemical process that kills all types of life. Disinfectants are generally distinguished from other antimicrobial agents such as antibiotics, which destroy microorganisms within the body, and antiseptics, which destroy microorganisms on living tissue. Disinfectants are also different from biocides—the latter are intended to destroy all forms of life, not just microorganisms. Disinfectants work by destroying the cell wall of microbes or interfering with their metabolism. It is also a form of decontamination, and can be defined as the process whereby physical or chemical methods are used to reduce the amount of pathogenic microorganisms on a surface. Disinfectants can also be used to destroy mi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standardized Test
A standardized test is a test that is administered and scored in a consistent, or "standard", manner. Standardized tests are designed in such a way that the questions and interpretations are consistent and are administered and scored in a predetermined, standard manner. Any test in which the same test is given in the same manner to all test takers, and graded in the same manner for everyone, is a standardized test. Standardized tests do not need to be high-stakes tests, time-limited tests, or multiple-choice tests. A standardized test may be any type of test: a written test, an oral test, or a practical skills performance test. The questions can be simple or complex. The subject matter among school-age students is frequently academic skills, but a standardized test can be given on nearly any topic, including driving tests, creativity, athleticism, personality, professional ethics, or other attributes. The opposite of standardized testing is ''non-standardized testing'', i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rideal–Walker Coefficient
The Rideal–Walker coefficient, now only of historical interest, is a figure expressing the disinfecting power of any disinfectant. It is the ratio of the dilution of the disinfectant that kills a microorganism to the dilution of phenol that kills the organism in the same time under identical conditions. The Rideal–Walker coefficient determines the phenol coefficient utilizing the method (test) described by English chemists Samuel Rideal (1863–1929) and J. T. Ainslie Walker (1868–1930). The arbitrary choice of contact time (sterilisation in 7.5 minutes), diluent (distilled water) and test organism (Salmonella typhi, then called Bacillus typhosa) did not reflect the conditions under which disinfectants were used. Because of this, impossibly high values were obtained for disinfectant activity and quoted by disinfectant manufacturers. The method was referred to by distinguished microbiologist Sir Ashley Miles as "...at best a grossly over-simplified answer to a very difficult ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harriette Chick
Dame Harriette Chick DBE (6 January 1875 – 9 July 1977) was a British microbiologist, protein scientist and nutritionist. She is best remembered for demonstrating the roles of sunlight and cod liver oil in preventing rickets. Biography Early life and education She was born in London, England as the fifth child of seven daughters and four sons of Samuel Chick and Emma Hooley, a Methodist family. Her father owned property and sold lace. The Chick children were brought up strictly with no frivolities and regular attendance at family prayers. All seven girls attended Notting Hill High School, a girls' school thought to be outstanding for its teaching in the sciences. Subsequently, six of the sisters including Harriette continued to study for university degrees. Another of them, Frances Wood, became a notable statistician. Harriette was enrolled at Bedford College, and then as a science student at University College London in 1894 and then proceeded to obtain her doctorate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sir Charles James Martin
Sir Charles James Martin (9 January 1866 – 15 February 1955) was a British scientist who did seminal work on a very wide range of topics including snake toxins, control of body temperature, plague and the way it was spread, dysentery, typhoid and paratyphoid, nutrition and vitamin deficiencies, proteins, and myxomatosis as a means of controlling rabbit populations. He was a director of the Lister Institute of Preventive Medicine, serving from 1903 to 1930. Early life Born in Wilmot House, Dalston, Hackney, North London he was the twelfth child of Josiah (an insurance company actuary) and Elizabeth Mary Martin (née Lewis), Charles James was part of an extended family of children from his parents' previous marriages. Being a delicate child, he was sent off to a private boarding school in Hastings. At 15 he was employed as a junior clerk at the insurance firm where his father worked. He studied mathematics as a requirement for a future as actuary, but showed no special aptitud ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rate Equation
In chemistry, the rate law or rate equation for a reaction is an equation that links the initial or forward reaction rate with the concentrations or pressures of the reactants and constant parameters (normally rate coefficients and partial reaction orders). For many reactions, the initial rate is given by a power law such as :v_0\; =\; k mathrmx mathrmy where and express the concentration of the species and usually in moles per liter (molarity, ). The exponents and are the partial ''orders of reaction'' for and and the ''overall'' reaction order is the sum of the exponents. These are often positive integers, but they may also be zero, fractional, or negative. The constant is the reaction rate constant or ''rate coefficient'' of the reaction. Its value may depend on conditions such as temperature, ionic strength, surface area of an adsorbent, or light irradiation. If the reaction goes to completion, the rate equation for the reaction rate v\; =\; k cex cey applies thr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
