Abbott's Formula
Abbott's Formula - Related Videos
02:52
Chemical Formulas
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2020
A chemical formula presents information about the proportions of atoms constituting a particular chemical compound or molecule, mainly using symbols of elements and numbers. At times other symbols, such as dashes, parentheses, brackets, commas, plus, and minus signs, are also used. A chemical formula can be one of three types – molecular, empirical, and structural. Molecular Formula The molecular formula represents a molecule or a chemical compound using chemical symbols (to indicate the...
03:34
Ionic Compounds: Formulas and Nomenclature
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2020
An element composed of atoms that readily lose electrons (a metal) can react with an element composed of atoms that readily gain electrons (a nonmetal) to produce ions through complete electron transfer. The compound formed by this transfer is stabilized by the electrostatic attractions (ionic bonds) between the oppositely charged ions. Moving from the far right to the left on the periodic table, nonmetal elements often gain electrons to form anions with the same number of electrons as an atom...
03:10
Molecular Compounds: Formulas and Nomenclature
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2020
Molecular compounds or covalent compounds result when atoms share electrons to form covalent bonds. Since there is no electron transfer, molecular compounds do not contain ions; instead, they consist of discrete, neutral molecules. Since covalent compounds are formed from the combination of nonmetals, the periodic table can help recognize many of them. The position of a compound’s elements in the periodic table can predict whether the compound is ionic or covalent (although there are...
07:05
Determining the Empirical Formula
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2023
Source: Laboratory of Dr. Neal Abrams - SUNY College of Environmental Science and Forestry Determining the chemical formula of a compound is at the heart of what chemists do in the laboratory every day. Many tools are available to aid in this determination, but one of the simplest (and most accurate) is the determination of the empirical formula. Why is this useful? Because of the law of conservation of mass, any reaction can be followed gravimetrically, or by change in mass. The empirical...
02:37
Experimental Determination of Chemical Formula
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2020
The elemental makeup of a compound defines its chemical identity, and chemical formulas are the most concise way of representing this elemental makeup. When a compound’s formula is unknown, measuring the mass of its constituent elements is often the first step in determining the formula experimentally. Determination of Empirical Formulas The most common approach to determining a compound’s chemical formula is first to measure the masses of its constituent elements. However, chemical formulas...
FAQs
Control mortality establishes the background death rate that occurred without the tested treatment. Subtracting this value prevents naturally occurring or experimental-condition-related deaths from being attributed entirely to the pesticide, pollutant, or other stressor. The resulting estimate therefore focuses more specifically on mortality associated with exposure, improving comparisons between treated and untreated groups.
The term 100 minus control mortality represents the proportion of organisms that remained alive in the untreated group. Dividing by this value adjusts the treatment-related difference relative to the population that could still experience treatment effects. This step prevents the correction from treating all initial organisms as equally available for additional mortality.
Treatment-group mortality includes both deaths associated with exposure and deaths that also occurred under control conditions. Abbott's Formula removes the control-group component and rescales the remaining difference, so the reported percentage better represents treatment-related mortality. This distinction is important when background mortality would otherwise exaggerate the apparent toxicity or effectiveness of a treatment.
The calculation requires mortality percentages from two comparable groups: organisms exposed to the treatment and organisms maintained under untreated control conditions. Researchers then insert those values into the correction equation, subtracting control mortality from treatment mortality and dividing by the percentage surviving in the control. The final value is expressed as corrected mortality.
The method is useful when laboratory bioassays evaluate pesticides, pollutants, or other environmental stressors using insects or aquatic organisms. It helps researchers account for deaths that occur without the tested exposure, allowing toxicity or treatment effectiveness to be compared more reliably across experimental groups. Its value is greatest when control mortality is present but treatment effects must still be separated.
Corrected mortality provides a common basis for comparing treatment groups whose controls experience background deaths. In environmental toxicology, this supports clearer evaluation of how strongly different pesticides, pollutants, or other stressors affect test organisms. The adjusted results can help distinguish differences in treatment impact from differences caused by mortality occurring under the experimental conditions themselves.