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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] |
Disinfectant
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 m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microorganism
A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in older texts. The informal synonym ''microbe'' () comes from μικρός, mikrós, "small" and βίος, bíos, "life". is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells. The possible existence of unseen microbial life was suspected from ancient times, such as in Jain scriptures from sixth century BC India. The scientific study of microorganisms began with their observation under the microscope in the 1670s by Anton van Leeuwenhoek. In the 1850s, Louis Pasteur found that microorganisms caused food spoilage, debunking the theory of spontaneous generation. In the 1880s, Robert Koch discovered that microorganisms caused the diseases tuberculosis, cholera, diphtheria, and anthrax. Because mi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 shows ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diluent
A diluent (also referred to as a filler, dilutant or thinner) is a Concentration, diluting agent. Certain fluids are too Viscosity, viscous to be pumped easily or too density, dense to flow from one particular point to the other. This can be problematic, because it might not be economically feasible to transport such fluids in this state. To ease this restricted movement, diluents are added. This decreases the viscosity of the fluids, thereby also decreasing the pumping/transportation costs. One industrial application is the transport of crude oil via pipelines. Heavy crude oil/bitumen are fluids with high viscosity, especially at low temperatures. The addition of a diluent enables the diluted fluid (dilbit in the case of bitumen) to meet pipeline specifications in order for it to be efficiently transported. Typical diluent in this case is naphtha or Natural gas condensate, condensate. Types of diluents more familiar to the general public include paint thinner and nail polish ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salmonella Typhi
''Salmonella enterica'' subsp. ''enterica'' is a subspecies of ''Salmonella enterica'', the rod-shaped, flagellated, aerobic, Gram-negative bacterium. Many of the pathogenic serovars of the ''S. enterica'' species are in this subspecies, including that responsible for typhoid. Serovars ''S. enterica'' subsp. ''enterica'' contains a large number of serovars which can infect a broad range of vertebrate hosts. The individual members range from being highly host-adapted (only able to infect a narrow range of species) to displaying a broad host range. A number of techniques are currently used to differentiate between serotypes. These include looking for the presence or absence of antigens, phage typing, molecular fingerprinting and biotyping, where serovars are differentiated by which nutrients they are able to ferment. A possible factor in determining the host range of particular serovars is phage-mediated acquisition of a small number of genetic elements that enable infection of a pa ... [...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 i ... [...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 (disease), 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, London Borough of Hackney, 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 futur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 shows ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
