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Mass spectra of creatine (molecular weight 131) obtained by (a) electron impact, (b) chemical ionization, (c) field ionization, and (d) field desorption with moderate heating. Both the molecular ion (not observed in a) and the M + 1 ion in b, c, and…

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from article Mass spectrometry

Representative gas-phase proton affinities of molecules.

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from article Mass spectrometry

Potential well of a molecule: (a) undistorted, with ionization potential I near a metal with work function ϕ in the absence of a field gradient; and (b) in a strong field gradient. Near the metal surface the external field raises the most weakly…

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from article Mass spectrometry

Use of isotope distribution to determine elemental composition. (a) Molecular ion for a compound containing one bromine atom. (b) Molecular ion for a compound containing two bromine atoms. (c) Molecular ion for a compound containing neither bromine…

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from article Mass spectrometry

Mass spectra of (a) acetophenone and (b) valerophenone, using electron impact.

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from article Mass spectrometry

Scale-expanded portion of acetophenone spectrum showing a broad metastable ion at m/e 56.5.

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from article Supramolecular chemistry

Schematic representation of the self-assembly of a tricompartmental cagelike architecture by coordination of 7 ligands of two different types and 12 Cu(I) metal ions: R groups are omitted for clarity on the assembled entity (right). (After P. N. W.…

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from article Centrifugation

Laboratory centrifuge. (Credit: McGraw-Hill Education)

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from article Centrifugation

Centrifuge used in the development of new therapeutic molecules based on human antibodies for the treatment of infectious and inflammatory diseases, Biotherapix, Grupo Genetrix, Madrid, Spain. (Credit: Pixtal/AGE Fotostock)

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from article Boron

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from article Diamond thin films

Diamond thin films. (a) Nucleation and growth of a diamond thin film. (b) Scanning electron microscope side view image of a 400-nm-thick diamond thin film grown on a silicon substrate. (Wensha Yang, University of Wisconsin-Madison)

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from article Diamond thin films

Scanning electron microscope images of two diamond films, showing the individual diamond crystallites that agglomerate into a continuous film. (a) Very small diamond grains. (b) Film with larger diamond crystals. (Bin Sun, University of…

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from article Metallochaperones

A family of copper metallochaperones direct the trafficking of copper ions inside the cell. The schematic shows three distinct pathways of copper movement within a eukaryotic cell. Copper is first transported into the cell by the cell-surface copper…

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from article Science

Italian physicist and astronomer Galileo Galilei (1564–1643) founded the modern scientific method of deducing laws to explain the results of observation and experiment. (Credit: Getty Images)

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from article Rhenium

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from article Infrared spectroscopy

Mid-infrared absorption spectra recorded on a Fourier-transform spectrometer at a resolution of 1 cm−1. (a) Polystyrene film, 0.05 mm thick. The weak intensity fluctuations between 2000 and 2800 cm−1 are interference fringes, caused by reflections…

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from article Infrared spectroscopy

Basic single-beam recording infrared prism spectrometer. The monochromator (the portion from the entrance slit S1 to the exit slit S2) is a Littrow mounting, a common arrangement for infrared instruments.

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from article Infrared spectroscopy

Spectrum of the ν1 + ν5 rotation–vibration band of acetylene recorded with a grating spectrometer, resolution 0.05 cm−1; gas at 25°C and 100-torr (13.3-kPa) pressure, 25-cm (10-in.) path length. The letters indicate features that are discussed in…

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from article Xenon

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from article Dialysis

Equipment for dialysis.

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from article Carbon

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from article Carbon

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from article Carbon

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from article Solution

Fugacity and mole fraction. Line A, ideal. Line B, typical nonideal. Line C, Henry's law.

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from article Adsorption

Particle adsorption on polymer hydrogel surface. [Credit: N. Sato et al., Sci. Rep., 2017 (CC BY 4.0)]

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from article Adsorption

One-dimensional potential energy curves typical for hydrogen molecules (H2) and atoms (H) as they approach the surface of a metal substrate. The solid curve, which involves a crossing from the molecular curve to the atomic curve, shows the type of…

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from article Adsorption

Analogy between the bonding of (a) the ethylidyne ligand (CCH3) to a rhodium (Rh) single crystal surface and (b) to a cobalt carbonyl cluster [H3CC(Co)2(CO)7]. The bond lengths and angles, as determined by diffraction techniques, are virtually…

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from article Adsorption

Scanning tunneling micrographs of 5× 2.25 nanometer areas of (a) the basal plane of a graphite surface and (b) the same surface after being covered with a liquid drop of 1-triacontanol. The bright spots in (a) correspond to every other carbon atom…

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from article Radiation chemistry

Variation of G with linear energy transfer (LET) for the products solvated electron (e−aq), OH, H2O2, H, and H2. (After R. C. Cooper and R. W. Wood, eds., Physical Mechanisms in Radiation Biology, National Technical Information Service, 1974)

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from article Radiation chemistry

Growth and decay of the signal of naphtholate anion in the pulse irradiation of a naphthol solution. Deter- mination of the decay rate gives a spontaneous lifetime of 30 milliseconds for loss of the naphthol proton in aqueous solution.

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from article Radiation chemistry

Time dependence of the electron spin resonance signals of hydrogen atoms in the presence of 50–600-micromolar azide ion. The signal intensities and decay periods decrease with increasing azide ion concentration.

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from article Transition elements

Portion of periodic table showing transition elements, their atomic number, symbol, and electron configurations in valence shells; heavy border indicates the more restricted classification.

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from article Transition elements

Physical properties of transition elements as function of their atomic number.

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from article Toxicology

Toxicologists study the adverse effects of chemical and physical agents on living organisms. In this photograph, a turtle is covered in petroleum following an oil spill. (Credit: Getty Images)

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from article Toxicology

Fish killed by chemically contaminated waters. (Credit: National Oceanic and Atmospheric Administration)

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from article Toxicology

The movement of mercury in the environment. In nature, mercury vapor (Hg0) is a stable gas and evaporates from the Earth's surface (both soil and water). Moreover, anthropogenic sources are a significant contributor to atmospheric mercury, and these…

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from article Gas and atmosphere analysis

Collection devices for monitoring air in the workplace. (a) Solid sorbent (charcoal) sampling tube. (b) Midget impinger. (c) Cowled cassette and its filter. (d) Passive monitor, used for nitrogen dioxide. (e) Piston-type detector tube pump.

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from article Gas and atmosphere analysis

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from article Gas and atmosphere analysis

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from article Gas and atmosphere analysis

Evacuated-flask sampling system.

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from article Zirconium

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from article Controlled/living radical polymerization

Free-radical polymerization.

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from article Controlled/living radical polymerization

Active and dormant radical equilibrium.

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from article Controlled/living radical polymerization

Nitroxide-mediated radical polymerization of styrene or butylacrylate.

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from article Controlled/living radical polymerization

Atom transfer radical polymerization.

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from article Controlled/living radical polymerization

RAFT polymerization.

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from article Menthol

Enantioselective synthesis of /(−) menthol.

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from article Gel permeation chromatography

Gel permeation chromatograph.

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from article Gel permeation chromatography

Typical gel permeation chromatogram with a calibration curve.

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from article Gel permeation chromatography

Typical triple chromatogram obtained by using both light scattering and viscometric detectors in addition to a concentration detector.

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from article Morphine alkaloids

Biosynthesis of thebaine.

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from article Osmoregulatory mechanisms

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from article Osmoregulatory mechanisms

The kidney helps to eliminate water and waste products from the body. During osmoregulation in this organ, numerous smaller functional units, called urinary tubules or nephrons, allow water to be moved across cell membranes from a lower to a higher…

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from article Carborane

Parent clusters from which carborane structures are determined. The diagonal lines define series of related closo, nido, and arachno structures.

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from article Carborane

Skeletal structures of the (a) 1,2-, (b) 1,7-, and (c) 1,12-isomers of C2B10H12.

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from article Carborane

Vertex boron atom with the three sp3 orbitals that it employs in cluster bonding. The BH unit contributes three orbitals and only two electrons to the bonding that holds the cluster together (framework bonding).

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from article Carborane

Three resonance structures of nido-C2B4H8.

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from article Carborane

Skeletal structures of the tetracarbon carboranes, R4C4B8H8.

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from article Carborane

Skeletal structures. (a) [nido-7,8-C2B9H12]−. (b) [nido-7,9-C2B9H12]−. (c) [nido-C2B10H12]2− anions. (d) (C2B9H11)2MN-4 complexes, where N = oxidation state of the metal.

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from article Agricultural chemistry

Agricultural chemistry often involves the use of fertilizers to improve agricultural output and productivity. Urea (carbamide) fertilizers are notable sources of nitrogen, which is necessary for healthy plant growth and well-balanced soil…

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from article Diffusion

Beakers of water before and after diffusion. (Credit: McGraw-Hill Education/Charles D. Winters)

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from article Diffusion

Diffusion in a tube of cross-sectional area A. The net rate of diffusion into the fluid between z and z + Δz is AJ(z) − AJ(z + Δz).

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from article Emulsion

An emulsion in which small oil (blue) droplets are dispersed in an aqueous liquid.

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from article Molecular isomerism

Functional isomers.

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from article Molecular isomerism

Positional isomers.

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from article Molecular isomerism

Skeletal isomers. (a) Chain isomers. (b) Ring isomers.

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from article Molecular isomerism

Enantiomers, mirror-image isomers.

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from article Molecular isomerism

Diastereomers, isomers having different spatial arrangements of the same groups of atoms.

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from article Molecular isomerism

Energy barriers between isomers A and B.

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from article Molecular isomerism

Easily interconverted isomers. (a) Ethyl acetoacetate. (b) Cyclooctatriene and bicyclooctadiene.

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from article Molecular isomerism

Conformational isomers.

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from article Iron

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from article Iron

Limonite, an ore of iron. (Credit: Alex Demas/USGS)

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from article Surface tension

Capillary rise of water in tubes with different diameters. (McGraw-Hill Education)

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from article Surface tension

Contact angle. (a) Liquid wets solid. (b) Liquid does not wet solid.

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from article Surface tension

Rise of liquid in capillary tube.

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from article Chicle

Fruit of Manilkara zapota. (After L. H. Bailey, The Standard Cyclopedia of Horticulture, vol. 3, Macmillan, 1937)

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from article Membrane mimetic chemistry

Simplified representation of organized aggregates formed from surfactants. (a) Monoloyer. (b) Spherical micelli. (c) Rodlike micelle. (d) Reversed micelli. (e) Water-in-oil microemulsion. (f) Oil-in-water microemulsion. (g) Bilayer lipid membrane.…

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from article Neptunium

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from article High-pressure chemistry

Range of existing natural high pressures. 1 bar = 102 kPa.

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from article High-pressure chemistry

Basic types of static high-pressure equipment. (a) Bridgman anvil. (b) Piston and cylinder. (c) Belt design. (d) Tetrahedral design.

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from article Hydrogen

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from article Nonstoichiometric compounds

Formation of Na1+δCl by incorporation of a neutral sodium atom as Na+; at a vacant cation site and an e− at a vacant anion site. The +'s represent sodium ions, and the −'s represent chloride ions.

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from article Nonstoichiometric compounds

Formation of NaCl1+δ by incorporation of a neutral chlorine atom at a vacant anion site and migration of an electron from some chloride ion in the normal structure of the crystal.

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from article Nonstoichiometric compounds

Free energy versus composition for a two-element system forming the nonstoichiometric compound AB1+δ. Temperature and pressure are constant.

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from article Nonstoichiometric compounds

Temperature-composition plot showing phase relations for formation of the nonstoichiometric compound AB1+ε. The tinted region corresponds to a single solid phase of variable composition.

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from article Nonstoichiometric compounds

Cobalt-deficient cobaltous oxide, Co1−δO. The squares represent missing cobalt atoms. Note the presence of two Co3+ to compensate for each Co2+ missing.

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from article Nonstoichiometric compounds

How nonstoichiometry arises in TiO1±δ. The squares represent vacant lattice sites, and the tint indicates added atoms.

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from article Radiochemical laboratory

Radiochemical laboratory, hood-equipped, with rubber-gloved openings. (Argonne National Laboratory)

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from article Radiochemical laboratory

Fume hood set up with portable shielding and small tongs for working with low-level beta- and gamma-emitting isotopes. (Brookhaven National Laboratory)

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from article Radiochemical laboratory

Exterior view of two hot cells with manipulators. The walls are 7-in.-thick (17.75-cm) lead, encased in 1/4-in.-thick (0.6-cm) steel plate. The lead glass windows are 14 in. (35.5 cm) thick and provide shielding equivalent to the walls. (Brookhaven…

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from article Battery

An assortment of common electric battery types. (Credit: Reed Richards / Alamy)

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from article Battery

Diagram of a zinc-alkaline-manganese dioxide cylindrical cell.

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from article Organic photochemistry

Reaction scheme of three rapidly interconvertible, nonseparable conformers and their yields of specific photoproducts, showing the composition of the photoproduct mixture (in percent) of the Z isomer of 2,5-dimethylhexa-1,3,5-triene after 10%…

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from article Organic photochemistry

Benzophenone as a triplet sensitizer for an olefin. Symbols are explained in the text.

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from article Organic photochemistry

Energy curves of the ground state (S0) and the first excited singlet state (S1) of the photoreaction. By a jump from the first excited singlet state to the ground state, the product (P) or reactant (A) can be attained.

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from article Emission spectrochemical analysis

Inductivity coupled radio-frequency plasma.

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from article Scientific methods

Fig. 1. A scientific investigator examining laboratory samples. (Credit: nandyphotos/Getty Images)

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from article Scientific methods

Portrait of scientist Francis Bacon at the age of 66. Bacon advanced challenging views of the scientific method. (Courtesy of Rijksmuseum, Amsterdam)

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from article Biological oxidation

Biological oxidation and reduction reactions (collectively called redox reactions) occur simultaneously, and one does not occur without the other. An oxidized substance (or atom), that is, one in which there is the loss of an electron, loses energy;…

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