Acid number: defined

A sample of polyester (ca. 1 g, exactly weighed) is dissolved in 20 mL toluene-ethanol mixture (1/1 vol.) and titrated by a solution of KOH in ethanol (0.05 mol/L) using a potentiometric titrator. A blank titration must be performed under the same conditions. Hardly soluble polyesters (e.g., PET) must be dissolved in an o-cresol-chloroform mixture or in hot benzyl alcohol.417 The result (acid content) is normally expressed in mmol COOH/g polyester but may also be given as the acid number, defined as the number of milligrams of KOH required to neutralize 1 g of polyester. [Acid number = (number of mmol COOH/g polyester) x 56.106.]... 

Acid number (ASTM D 974-80, DIN 51 558). The acid number is defined as the amount of potassium hydroxide in milligrams required to neutralize 1 g of resin under fixed conditions. 

The acid number is mainly defined for rosins and rosin-derived resins and for phenol-modified resins. Standard hydrocarbon resins have zero acid number because the absence of functional groups. However, the acid number allows one to control deterioration by oxidation with formation of carbonyl and carboxyl groups in hydrocarbon resins. Typical acid number values of different resin types are ... 

The method employed in these studies for determining acid number is described by Snell and Biffin (4). The acid number is defined as milligrams of alkali calculated as potassium hydroxide, required to neutralize the free acids in 1 gram of oil. ... 

Figure 13.4.4 Classification of H atoms in 4,4-difluorobutanoic acid as defined in the model of Ghose et al. [49,50], The subscript represents hybridization and the superscript is the formal oxidation number. X represents any heteroatom (O, N, S, P, Se, and halogens).

The regulation passed (in Italy) in 1894 defines the conclusions to be drawn from certain of the estimations mentioned above. Thus, as regards the volatile acid number butters the fat of which requires not less than 26 c.c. of N/10-alkali are to be regarded as genuine, when there are no contrary indications less than 20 c.c. indicates adulteration values between 20 and 26 are suspicious, when the other data (age of the butter, season of the year, etc.) do not permit of a decision. In such a case it is advisable, where possible, to examine a genuine sample of butter from the same source, provided that this can be obtained shortly after the suspected butter. 

M] or [rh] Molecular rotation, defined as [a] x MW/100. Specific rotation corrected for differences in MW. The symbol [M] and the term molecular rotation are now deemed incorrect, and the term molar rotation denoted by [d ] is preferred. meso- Denotes an internally compensated diastereoisomer of a chiral compound having an even number of chiral centres, e.g., me o-tartaric acid. Formally defined as an achiral member of a set of diastereomers that also contains chiral members, mutarotation Phenomenon shown by some substances, especially sugars, in which the optical activity changes with time. A correct presentation is, e.g., [a]n ° + 20.3 -101.2 (2h)(c, 1.2 in HjO). 

Figure 1. The beta WD propeller. A) The repeat-defining sequence s most common amino acids, "x" indicates any amino acid. Number in brackets indicate the known variable range. B) The F-box WD-repeat protein 1p22.pdb (beta-TrCPI) with dark gray strand cartoons defining the extent of a full WD-repeat. Shown in light gray alpha helix cartoon is an inserted loop between two WD-repeats. In black are three strands of the C-terminal blade overlapped by a first strand formed from the N-terminal end of the WD-repeat domain. In black is the Velcro last strand overlapped by the first strand of the first repeat. C) Displays an edge-on view of the WD repeat and the F-box domain extending above the upper surface of the propeller. Also shown in atomic space fill is the repeat-defining Trp-Asp pair.

P12C-2 Use the references given in Ind. Eng. Chem. Prod. Res. Lev. /4, 226 (1975) to define the iodine value, saponification number, acid number, and experimental setup. Use the slurry reactor analysis to evaluate the effects of mass transfer and determine if there are any mass transfer limitations. 

Acid Number It is defined as the milligram of potassium hydroxide required to neutralise the free fatty acids present in one gram of fat or oil. Acid number indicates the amount of free fatty acids present in fat or oil. The free fatty acid content increases with age of the fat or oil. 

The presence of a considerable number of hydronium ions identifies an aqueous solution as acidic. A Swedish chemist, Svante Arrhenius, was among the first to recognize this fact. In 1890, he proposed that an acid be defined as any substance that, when added to water, increases the hydronium ion concentration. Later, you will learn about another way to define acids that goes beyond aqueous solutions. 

Acidity is determined through the acid number, which is the quantity of base, expressed in milligrams of potassium hydroxide per gram of sample, required to titrate a sample in the solvent from its initial meter reading to a meter reading corresponding to a freshly prepared nonaqueous basic buffer solution or a well-defined inflection point as specified in the test method. Test methods include potentiometric titration (ASTM D-66, IP 177) and indicator-indicator titration (ASTM D-974, IP 139) in addition to inorganic acidity (IP 182) and total acidity (IP 1) methods. 

A prerequisite for the catalytic function of an enzyme is its native tertiary structure which is determined by the number and sequence of amino acids (primary structure) forming the molecule. Favoured by hydrogen bonds, parts of the polypeptide chain exist in an a-helical or a (3-sheet structure (secondary structure). Most enzymes are globular proteins, the tertiary structure of which may be fixed by disulfide bonds between cysteine residues. A famous example is lysozyme (Fig. 20), consisting of 129 amino acids. A defined three-dimensional structure is... 

Water based poly(ester-imide) wire enamels were developed in the 1960s and 1970s. The resins were made water soluble in different ways. Resins with a defined acid number were neutralized with alkanolamines [144-148] or ammonia [149]. In another process the poly(ester-imide) resins were submitted to an ami-nolysis with alkanolamines [150-153] or ammonia [154-156], when the resin network is more or less degraded. Solvents for this poly(ester-imide) is water and usually a small amount of high boiling solvents like N-methylpyrrolidon or diethylene glycol monomethylether. Titanium catalysts stable to hydrolysis, like titanium-ammonium lactate and titanium lactate, were used [157]. To improve thermal and mechanical properties, phenol blocked isocyanates can be added to the water based poly(ester-imide)s. The blocked isocyanates are dispersed by means of an ethoxylated nonylphenol and are added to the water based wire enamel. Improvement of the property level is claimed [158]. 

What is the acid value of polycaprolactam (nylon-6) with average DF 500 [Note Acid value or acid number is defined as the number of milligrams of KOH required to neutralize 1 g of polymer.]... 

The chemistry of karaya has only recently begun to be intensively investigated. The early investigations of the gum are concerned mainly with its acidic nature. Karaya occurs as a partially acetylated derivative. The acid number has been found to vary from 13.4 to 22.7 (10, 11). The acid number is defined as the milligrams of alkali required to neutralize 1 gram of the gum. The volatile acidity of the gum is determined by repeated distillation of the water solution with phosphorle... 

Since the number of amino acid residues defined In consensus sequences are usually less than 10 residues, consensus sequences are too small as a unit of function and molecular evolution of proteins. Therefore sequence segments found In homology graphs are favored for sequence-function relationships over consensus sequences. 

Free and total acid are defined as the number of milliliters of 0.1 M NaOH needed to reach the first and second endpoint, respectively. 

AN, the acceptor number of Lewis acids, was defined as the relative P NMR shift obtained when triethylphosphine oxide (EtsPO) was dissolved in the eandidate acid. The scale was normalized by assigning an AN value of 0 to the NMR shift obtained with hexane, and 100 to that obtained from the SbCLrEtsPO interaetion in dilute 1,2-dichloroethane solution. However, the total shift of P NMR in two-eomponent systems has an appreciable contribution of van der Waals interactions that must be accounted for in correlating spectral shifts with heats of acid base interactions. Riddle and Fowkes [7] corrected the P NMR shifts for van der Waals interactions and proposed a new scale of acceptor numbers. The new AN values (AN—AN ) in ppm are converted into AN in kcal/mol units by... 

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