Acidifying principle

Boyle (1661) attempted to provide a more definite concept and attributed the sour taste of acids to sharp-edged acid particles. Lemery, another supporter of the corpuscular theory of chemistry, had similar views and considered that acid-base reactions were the result of the penetration of sharp acid particles into porous bases (Walden, 1929 Finston Rychtman, 1982). However, the first widely accepted theory was that of Lavoisier who in 1 111 pronounced that oxygen was the universal acidifying principle (Crosland, 1973 Walden, 1929 Day Selbin, 1969 Finston Rychtman, 1982). An acid was defined as a compound of oxygen with a non-metal. 

These two radicals ore the acidifying principles of nearly all orgmcic acids they are therefore highly important compounds. The atom of each consists of an atom of carbon, one bond of which... 

In the days of Lavoisier oxygen was the acidifying principle later hydrogen was considered the carrier of acid properties but, it is becoming increasingly obvious that, although these elements are important, they are not essential to the display of acid properties. 

Compounds of potassium had been known since ancient times potassium is acaially the seventh most abundant element in the Earth s crust. But this was the first time the metal had been seen and understandably so. Potassium metal reacts with moisture to form hydrogen gas, which catches fire from the heat of the reaction. Davy stored his reactive potassium under naphtha (today used as lighter fluid) and proceeded 2 days later to isolate sodium from caustic soda. But as often happens, Davy s solution of one puzzle provided another. Bases (materials referred to as caustic or alkali) react with acids to form salts and water, which makes them, so to speak, the opposites of acids. When Davy electrolyzed his bases, he found that oxygen was one of the products. Lavoisier had said that oxygen was the acidifying principle, but Davy now showed that it could equally well be considered the principle of bases. Davy dedicated the next 4 years to demonstrating that elements do not behave as principles in the manner Lavoisier had said. 

Cavendish does not point out that oxygen does not act as an acidifying principle in the formation of water, w hich is a neutral substance, but he appreciated what is really a weak point in Lavoisier s theory. Davy in 1810 was to show that marine acid does not contain any oxygen. Besides this, Cavendish also rejected a central part of Lavoisier s theory, the materiality of heat (see p. 308). ... 

In a criticism of the new nomenclature G. D Arejula especially emphasised the weakness of the assumption that all acids contain oxygen. From his results with prussic acid and sulphuretted hydrogen, Berthollet felt compelled to admit that, although oxygen may be regarded as the most usual acidifying principle, yet to conclude that all acidity is caused by it, even that of the muriatic, fluoric and boracic acids, is to press the limits of analogy too far . ... 

Lavoisier also says the acidifying and the acidified principle can exist in different proportions, which constitute the points of equilibrium and of saturation . He seems to have inclined to the idea of indefinite proportions in some special cases, and linked it in an interesting way with the operation of affinity in a manner afterwards developed by Berthollet, who was a co-author and participated in the discussions leading to this publication. 

The non-metal oxide reactions with water led Antoine Laurent Lavoisier (1713-1794) to associate the acidity principle with elemental oxygen, but Sir Humphry Davy, in the beginning of the XIX century, was the first to suggest that the acidifying principle was owed to hydrogen — as in the case of hydrochloric acid. 

In 1923, Brpnsted, following in the footsteps of Arrhenius who, apparently, was only concerned with the proton as the acidifying principle, proposed that an acid is a proton donor and a base is a proton acceptor. While we recognize that this is dramatically oversimplified given what we now know about solvent participation, it nonetheless remains a useful construct. Indeed, for materials that ionize, completely or otherwise, the add strength or addity is referred to as the position of equilibrium in the reaction of the acid with a base. Thus, for the generalized acid HA ionizing in water (H2O) Equation 5.6 can be written as... 

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