Coherence protection

There is considerable scholarly speculation on ancient precursors of copyright. However, no significant copyright protection existed in theory or practice until the development of the printing press, a means of mass dupHcation of creative work. The law did not need a coherent protective stmcture for written and graphic works when the only means of copying them, by hand, was so labor-intensive as to requite an investment potentially far in excess of the worth of the copy. 

Al, Ga, In and T1 differ sharply from boron. They have greater chemical reactivity at lower temperatures, well-defined cationic chemistry in aqueous solutions they do not form numerous volatile hydrides and cluster compounds as boron. Aluminium readily oxidizes in air, but bulk samples of the metal form a coherent protective oxide film preventing appreciable reaction aluminium dissolves in dilute mineral acids, but it is passivated by concentrated HN03. It reacts with aqueous NaOH, while gallium, indium and thallium dissolve in most acids. 

J. W. Goldschmidt. Finely powdered A1 metal explodes on contact with liquid O2, but for normal samples of the metal a coherent protective oxide film prevents appreciable reaction with oxygen, water or dilute acids amalgamation with Hg or contact with solutions of salts of certain electropositive metals destroys the film and permits further reaction. Aluminium is also readily soluble in hot concentrated hydrochloric acid and in aqueous NaOH or KOH at room temperature with liberation of H2. This latter reaction is sometimes written as... 

---