Arabic

AES ARABS Auger electron spectroscopy [77, 112-114, 117] Angle-resolved AES [85, 115] An incident high-energy electron ejects an inner electron from an atom an outer electron (e.g., L) falls into the vacancy and the released energy is given to an ejected Auger electron Surface composition... 

English, potash - pot ashes L.. kalium, Arab qali, alkali) Discovered in 1807 by Davy, who obtained it from caushc potash (KOH) this was the first metal isolated by electrolysis. 

The facilities for experimental work were poor, with inadequate wet laboratory space. In our discussions, I mentioned to Kaprielian my interest in significantly extending my previous work into the area of hydrocarbon chemistry. I felt that by establishing a strong program of basic research and graduate education in hydrocarbon chemistry, USC could become a leader in this important field. Because the memory of the first Arab oil embargo was still fresh, this struck a chord with Kaprielian, who felt that he could sell my research interest to the trustees and establish a Hydrocarbon Research Institute at USC that could accommodate me, as well as other chemistry faculty members whose interests could fit into its framework. 

Benzoic acid had been known for several hundred years by the time of Mitscher lich s experiment Many trees exude resinous materials called balsams when cuts are made m their bark Some of these balsams are very fragrant which once made them highly prized articles of commerce especially when the trees that produced them could be found only m exotic faraway lands Gum benzoin is a balsam obtained from a tree that grows m Java and Sumatra Benzoin is a word derived from the Erench equivalent benjoin which in turn comes from the Arabic luban jawi meaning incense from Java Benzoic acid is itself odorless but can easily be isolated from gum benzoin... 

For branching compounds, the parent structure is the longest continuous chain present in the compound. Consider the compound to have been derived from this structure by replacement of hydrogen by various alkyl groups. Arabic number prefixes indicate the carbon to which the alkyl group is attached. Start numbering at whichever end of the parent structure that results in the lowest-numbered locants. The arable prefixes are listed in numerical sequence, separated from each other by commas and from the remainder of the name by a hyphen. 

Ionic charge should be indicated by an Arabic superscript numeral preceding the plus or minus sign Mg2 +, PO -. 

Stoichiometric Proportions. The stoichiometric proportions of the constituents in a formula may be denoted by Greek numerical prefixes mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona- (Latin), deca-, undeca- (Latin), dodeca-,. . . , icosa- (20), henicosa- (21),. . . , tri-conta-(30), tetraconta-(40),. . . , hecta-(100), and so on, preceding without a hyphen the names of the elements to which they refer. The prefix mono can usually be omitted occasionally hemi-(1/2) and sesqui- (%) are used. No elisions are made when using numerical prefixes except in the case of icosa- when the letter i is elided in docosa- and tricosa-. Beyond 10, prefixes may be replaced by Arabic numerals. 

The names of addition compounds are formed by connecting the names of individual compounds by a dash (—) and indicating the numbers of molecules in the name by Arabic numerals separated by the solidus (diagonal slash). All molecules are cited in order of increasing number those having the same number are cited in alphabetic order. However, boron compounds and water are always cited last and in that order. 

Dichromated Resists. The first compositions widely used as photoresists combine a photosensitive dichromate salt (usually ammonium dichromate) with a water-soluble polymer of biologic origin such as gelatin, egg albumin (proteins), or gum arabic (a starch). Later, synthetic polymers such as poly(vinyl alcohol) also were used (11,12). Irradiation with uv light (X in the range of 360—380 nm using, for example, a carbon arc lamp) leads to photoinitiated oxidation of the polymer and reduction of dichromate to Ct(III). The photoinduced chemistry renders exposed areas insoluble in aqueous developing solutions. The photochemical mechanism of dichromate sensitization of PVA (summarized in Fig. 3) has been studied in detail (13). 

A wide variety of plant exudates have been used ia foods and medicines for centuries, including acacia, karaya, and ghatti. Plant gums derived from seeds iaclude arabic, guar, locust bean, tamatind, and tara. AH play a role ia fat replacement either singly or ia mixtures. 

The polysaccharides in gum arabic formed a medium used for illuminated manuscripts and inks (qv) as well as for painting. Gum is also the binder in watercolors. 

Gum Arabic. Gum arabic [9000-01-5] is an exudate of the Acacia tree, found in the Middle East. It dissolves readily in water to produce low viscosity solutions. It is used in confectionery products, bakery toppings, beverages, fro2en dairy products, and dry drink mixes (86). 

Gum Arabic. Gum arable [9000-01-5] is a dried exudate from a species of the acacia tree found in various tropical and semitropical areas of the world. Most of the commercial gum comes from a single species, Jicacia Senegal. The largest producers are the RepubHc of Sudan and several other West African countries, with over 75% of the world s production coming from the Sudan. The best grade comes from Jicacia Senegal and about 90% of the Sudan s production is from this source the remainder comes Jicacia sejal... 

Gum ghatti is the calcium and magnesium salt of a complex polysaccharide which contains L-arabinose, D-galactose, D-mannose, and D-xylose and D-glucuronic acid (48) and has a molecular weight of approximately 12,000. On dispersion in water, gum ghatti forms viscous solutions of viscosity intermediate between those of gum arabic and gum karaya. These dispersions have emulsification and adhesive properties equivalent to or superior to those described for gum arabic. 

In foods and pharmaceuticals, gum ghatti has been used in many appheations described for gum arabic, particularly as an emulsifier for oil and water emulsions (49). It has also been used as a waterproofing agent in Hquid explosives, and to stabilize paraffin wax emulsions. However, in the 1990s, gum... 

Larch Gum. Larch gum [37320-79-9] (larch arabinogalactan) is obtained by water extraction of the western larch tree, iLarix occidentalism the heartwood of which contains 5—35% on a dry wood basis. In the early 1960s, a countercurrent hot water extraction system was developed, and the gum was produced commercially by the St. Regis Paper Co. under the trade name Stractan. The potential production capacity of this gum is 10,000 t/yr based on the wood residues from the lumber industry. However, the product could not compete with gum arabic, and commercial production is now limited to small batches for a specific medical appHcation. 

Larch gum is readily soluble in water. The viscosity of these solutions is lower than that of most other natural gums and solutions of over 40% soHds are easily prepared. These highly concentrated solutions are also unusual because of their Newtonian flow properties. Larch gum reduces the surface tension of water solutions and the interfacial tension existing in water and oil mixtures, and thus is an effective emulsifying agent. As a result of these properties, larch gum has been used in foods and can serve as a gum arabic substitute. 

Larch arabinogalactan is approved in 21 CFR 172.610 as a food additive for use as an emulsifier, stabilizer, binder or bodying agent for essential oils and noimutritive sweeteners, flavor bases, nonstandardized dressings, and pudding mixes. It has also been used in the preparation of cosmetic and pharmaceutical dispersions and as an emulsifier in oil—water emulsions (69). Industrially, the main use has been in Hthography as a gum arabic substitute. 

Thus, at a concentration of 0.95 g Na2S /100 g solution, the solubihty of mercuric sulfide has increased to 2100 ppm. It is customary to use no greater than a 20% excess of the alkah sulfide. Because the particle size of the precipitated mercuric sulfide is so small, it is helpful to add a ferric compound such as ferric chloride or ferric sulfate to effect flocculation. Sometimes other flocculating agents (qv) may also be added, eg, starch or gum arabic. 

Table 1 Hsts representative examples of capsule shell materials used to produce commercial microcapsules along with preferred appHcations. The gelatin—gum arabic complex coacervate treated with glutaraldehyde is specified as nonedible for the intended appHcation, ie, carbonless copy paper, but it has been approved for limited consumption as a shell material for the encapsulation of selected food flavors. Shell material costs vary greatly. The cheapest acceptable shell materials capable of providing desired performance are favored, however, defining the optimal shell material for a given appHcation is not an easy task.

Complex Coacervation. This process occurs ia aqueous media and is used primarily to encapsulate water-iminiscible Hquids or water-iasoluble soHds (7). In the complex coacervation of gelatin with gum arabic (Eig. 2), a water-iasoluble core material is dispersed to a desired drop size ia a warm gelatin solution. After gum arabic and water are added to this emulsion, pH of the aqueous phase is typically adjusted to pH 4.0—4.5. This causes a Hquid complex coacervate of gelatin, gum arabic, and water to form. When the coacervate adsorbs on the surface of the core material, a Hquid complex coacervate film surrounds the dispersed core material thereby forming embryo microcapsules. The system is cooled, often below 10°C, ia order to gel the Hquid coacervate sheU. Glutaraldehyde is added and allowed to chemically cross-link the capsule sheU. After treatment with glutaraldehyde, the capsules are either coated onto a substrate or dried to a free-flow powder. 

Eig. 2. Elow diagram of a typical encapsulation process based on the complex coacervation of gelatin with gum arabic. 

Liquid food ingredients encapsulated are typically oil-soluble flavors, spices (see Flavors and spices), and vitamins (qv). Even food oils and fats are encapsulated (63). These core materials normally are encapsulated with a water-soluble shell material appHed by spray drying from water, but fat shell formulations are used occasionally. Preferred water-soluble shell materials are gum arabic, modified starch, or blends of these polymers with maltodextrins. Vitamins are encapsulated with 2ero bloom strength gelatin by spray drying. 

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