Main constituents

C, b.p. 156 C. The most important of the terpene hydrocarbons. It is found in most essential oils derived from the Coniferae, and is the main constituent of turpentine oil. Contains two asymmetric carbon atoms. The (- -)-form is easily obtained in a pure state by fractionation of Greek turpentine oil, of which it constitutes 95%. Pinene may be separated from turpentine oil in the form of its crystalline nitrosochloride, CioHigClNO, from which the ( + )-form may be recovered by boiling with aniline in alcoholic solution. When heated under pressure at 250-270 C, a-pinene is converted into dipentene. It can be reduced by hydrogen in the presence of a catalyst to form... 

On archaeological glass objects, layers of reaction products are formed and the main constituents of these cmsts are the less-soluble compounds such as siHca and calcium carbonate, which becomes calcium sulfate. 

Diosphenol [490-03-9] the main constituent of buchu leaves, is an example of a naturally occurring compound with tautomeric properties (286) ... 

Boehmite (OC-Aluminum Oxide-Hydroxide). Boehmite, the main constituent of bauxite deposits in Europe, is also found associated with gibbsite in tropical bauxites in Africa, Asia, and Austraha. Hydrothemial transformation of gibbsite at temperatures above 150 °C is a common method for the synthesis of weU-cry stalhzed boehmite. Higher temperatures and the presence of alkali increase the rate of transfomiation. Boehmite ciy stals of 5—10 ]liii size (Fig. 3) are produced by tliis method. Fibrous (acicular) boehmite is obtained under acidic hydrothemial conditions (6). Excess water, about 1% to 2% higher than the stoichiometric 15%, is usually found in hydrothemiaHy produced boehmite. 

It is important to note that reinforced plastics remain a combination of materials differing in form or composition on a macro scale. The main constituents (resin, reinforcement, and filler) retain their identities and do not dissolve or merge into each other rather, they act in concert. These components can be physically identified and exhibit an interface between each other. 

Butadiene—Acrylonitrile Latices. Nitrile latices are copolymers of butadiene and acrylonitrile ia which those copolymerized monomers are the main constituents (see Elastomers, synthetic-nitrile rubber). The latices differ mainly ia ratio of comonomer and stabilizer type. They can be classified as low and medium acrylonitrile (ACN) types. The latter contain 35—40 wt % nitrile mbber, and low types ca 27—29 wt %. 

Deposits. Selenium forms natural compounds with 16 other elements. It is a main constituent of 39 mineral species and a minor component of 37 others, chiefly sulfides. The minerals are finely disseminated and do not form a selenium ore. Because there are no deposits that can be worked for selenium recovery alone, there are no mine reserves. Nevertheless, the 1995 world reserves, chiefly in nonferrous metals sulfide deposits, are ca 70,000 metric tons and total resources are ca 130,000 t (24). The principal resources of the world are in the base metal sulfide deposits that are mined primarily for copper, zinc, nickel, and silver, and to a lesser extent, lead and mercury, where selenium recovery is secondary. 

Patchouli alcohol. Patchouli oil comes from Pogostemonpatchouli and the main constituent is patchouli alcohol [5986-55-0] (105) or patchoulol. Another component of the essential oil is norpatchoulenol (106), a norsesquiterpene derivative as a minor (3—5%) constituent, important ia determining the overall odor of the essential oil (197). The price of patchouli oil ia 1995 was 20.90/kg from Indonesia (69). Alarge proportion of the oil (40—60%) is comprised of sesquiterpene hydrocarbons that do not have much odor value. World production of the oil was at about 750 t ia 1984. It is valuable ia perfumery bases because of its characteristic woody, herbaceous odor (198). 

Guaiol and Bulnesol. The main constituents of guaicwood oil are the sesquiterpene alcohols guaiol [489-86-1] (107) and bulnesol (108). When the alcohols are dehydrated with acid, many of the hydrocarbons formed are also found ia patchouli oil. 

Polymeric isocyanates or PMDI ate cmde products that vary in exact composition. The main constituents are 40—60% 4,4 -MDI the remainder is the other isomers of MDI, trimeric species, and higher molecular weight oligomers. Important product variables are functionaHty and acidity. Rigid polyurethane foams are mainly manufactured from PMDI. The so-called pure MDI is a low melting soHd that is used for high performance polyurethane elastomers and spandex fibers. Liquid MDI products are used in RIM polyurethane elastomers. 

Perfumes and Cosmetics. Vanillin, a crystal, is the main constituent of the vanilla bean. Its importance can be illustrated by the fact that human preferences in fragrances and in flavors, as determined by various studies, comprise three main smells or tastes rose, vanilla, and strawberry. 

Internal Sizing. The most widely used internal sizes are alkyl ketene dimers (AKD), alkenylsuccinic anhydrides (ASA), and rosin-based sizes that are used with papermaker s alum (aluminum sulfate with 14 waters of hydration), polyaluminum chloride (PAG), or polyaluminum siUcosulfate (PAS) (61). The rosin-based sizes are used under acidic conditions. Since the mid 1980 s there has been a steady conversion from acid to alkaline paper production, resulting in static to declining demand for the rosin-based sizing systems. Rosin is a complex mixture of compounds and consists primarily of monocarboxyhc acids with alkylated hydrophenan threne stmctures (62). A main constituent of wood rosin, gum rosin and taH-oil rosin is abietic acid. 

The formation of photodimers of the cyclobutane type from thymine (111 R = Me) occurs most effectively when a frozen aqueous solution of the substrate is irradiated. After the independent recognition of such dimers in two laboratories about 1960, it was some six years before the main constituent was identified beyond doubt (66JCS(C)2239) as the cis-syn entity (113), a U-shaped molecule in which the planes of the six-membered rings... 

Methane is the main constituent, with a boiling point of 119 K (—245°F). Ethane, with a boiling point of 184 K (—128°F) may be present in amounts up to 10 percent propane, with a boiling point of 231 K (—44°F), up to 3 percent. Butane, pentane, hexane, heptane, and octane may also be present. Physical properties of these hydrocarbons are given in Sec. 2. 

Vitreous, hard, chemically-resistant free silica, the most common form in nature. The main constituent in sandstone, igneous rocks, and common sands. 

The nuclei of iron are especially stable, giving it a comparatively high cosmic abundance (Chap. 1, p. 11), and it is thought to be the main constituent of the earth s core (which has a radius of approximately 3500 km, i.e. 2150 miles) as well as being the major component of siderite meteorites. About 0.5% of the lunar soil is now known to be metallic iron and, since on average this soil is 10 m deep, there must be 10 tonnes of iron on the moon s surface. In the earth s crustal rocks (6.2%, i.e. 62000ppm) it is the fourth most abundant element (after oxygen, silicon and aluminium) and the second most abundant metal. It is also widely distributed. 

Turpentine Oil.—This is readily recognised in oils which contain no pinene, as this is the main constituent of turpentine oil. It is usually found in the first distillates, and generally reduces the specific gravity and effects the solubility and optical rotation. Its presence is proved by the formation of pinene hydrochloride (melting-point 125°) and the nitro-sochloride (melting-point 103°). If pinene is a constituent of the oil itself, the addition of turpentine can only be proved by comparison with an authentic sample. 

Naphtha from atmospheric distillation is characterized by an absence of olefinic compounds. Its main constituents are straight and branched-chain paraffins, cycloparaffms (naphthenes), and aromatics, and the ratios of these components are mainly a function of the crude origin. 

The main constituents of kerosines obtained from atmospheric and... 

The scope of the term stainless steel has not been precisely defined, but for general purposes it may be considered to include alloys whose main constituent is iron but which also contain not less than 10% Cr. As with low-alloy steels, a distinction between low or medium carbon grades and high carbon grades must also be drawn, the latter being more in the nature of alloy cast irons. These are used mainly for oxidation resistance at high temperatures and for applications where abrasion resistance allied to a certain amount of corrosion resistance is required, and will not be considered in this section. 

Composition The main constituent of the film is aluminium oxide, in a form which varies in constitution between amorphous AljO, and 7-AI2O3, together with some monohydrate, AI2O3.H2O. In the presence of moisture, both the anhydrous forms are gradually transformed into the monohydrate, and the water content of as-formed films is, therefore, somewhat variable. 

Methane, the main constituent of natural gas, has the formula CH4. Its combustion products are carbon dioxide and water. 

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