Amphoteric, definition

These rules must be supplemented by the following two amphoteric rules already discussed in section 2.3.2.1, which supplement the definition of electron acceptor and electron donor adsorbates. 

The elements show increasing metallic character down the group (Table 14.6). Carbon has definite nonmetallic properties it forms covalent compounds with nonmetals and ionic compounds with metals. The oxides of carbon and silicon are acidic. Germanium is a typical metalloid in that it exhibits metallic or nonmetallic properties according to the other element present in the compound. Tin and, even more so, lead have definite metallic properties. However, even though tin is classified as a metal, it is not far from the metalloids in the periodic table, and it does have some amphoteric properties. For example, tin reacts with both hot concentrated hydrochloric acid and hot alkali ... 

The two distinctive affinities in the surfactant molecule mentioned above serve as the basis for the commonly accepted definition of surfactant groups. According to the charge of their hydrophilic moiety, surfactants can be classified into four categories anionic, non-ionic, cationic and amphoteric. 

In very general terms, petroleum is a mixture of (1) hydrocarbon types, (2) nitrogen compounds, (3) oxygen compounds, (4) sulfur compounds, and (5) metallic constituents. Petrolenm prodncts are less well defined in terms of heteroatom compounds and are better defined in terms of the hydrocarbon types present. However, this general definition is not adequate to describe the true composition as it relates to the behavior of the petroleum, and its products, in the environment. For example, the occnrrence of amphoteric species (i.e., compounds having a mixed acid-base natnre) is not always addressed, nor is the phenomenon of molecnlar size or the occnrrence of specific functional types that can play a major role in petrolenm behavior. 

Charging Hydroxylated Surfaces Definition of IEP(s). A hydroxyl-ated surface should be expected on all oxidic materials which have had a chance to come to equilibrium with an aqueous environment. Charge can develop on a hydroxylated surface through amphoteric dissociation of the surface hydroxide groups. Dissociation reactions can be written as follows, where underscored symbols refer to species forming part of the surface. Symbols not underscored refer to species assumed aqueous unless otherwise specified. 

Definition of Acids and Bases 222 Conjugate Acid-Base Pairs 222 Amphoteric Species 224 Strong Acids 225 Strong Bases 225 Weak Acids 226 Weak Bases 226 Polyprotic Acids 227 Acid and Base Strength Ka and Kb 228 Acid/Base Strength of Conjugate Acid-Base Pairs 230 Acid-Base Reactions 231... 

This is an amphoteric compound because it behaves as both an acid and a base in the Bronsted definition. As an acid, it can donate an H+ and becomes the conjugate base ... 

Amphiphilic compounds as surfactants, 21 Amphoteric surfactant, definition, 386 Analysis speed, importance, 125 Anionic surfactants definition, 387... 

Yellow amorphous powder, no definite mp, decomp 160 ( +216. uv max (80% methanol) 383 nm (Ej 9] 6). An amphoteric compd. Almost insol in water, benzene, chloroform, dry lower aliphatic alcohols, ether sol in basic solvents such as pyridine, collidine, and in aq lower alcohols. In coned H1S04 gives stable blue color no coloration with ferric chloride or with HO LDW i. v. in mice (using sodium carbcxymethyl cellulose as a vehicle) 6. ] 6 tng/kg, Williams et al, Antimicrob. Ag, Ckemother. 1964, 737-741. Also reported as LDjq i.v> in Swiss mice (using a colloidal suspension) 1,20 mg/kg, A. C, Parekh, C, V. Dave loc. cit. 

The similarity and complexity of the boric and silicic acids is notable. Boric acid, B(OH)3, is weakly but definitely acidic, and not amphoteric, whereas Al(OH)3 is mainly basic with some amphoteric behavior. 

The trivalent state is the characteristic one for all the lanthanides. They form oxides, M203, which resemble the Ca-Ba group oxides and absorb carbon dioxide and water from the air to form carbonates and hydroxides, respectively. The hydroxides, M(OH)3, are definite compounds, having hexagonal structures, and not merely hydrous oxides. The basicities of the hydroxides decrease with increasing atomic number, as would be expected from the decrease in ionic radius. The hydroxides are precipitated from aqueous solutions by ammonia or dilute alkalis as gelatinous precipitates. They are not amphoteric. 

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