Home › Acids › Calcination

Calcination

The separation or be the dry weight of the pulp. expulsion, by heat, of volatile from fixed matter. By this means crystalline salts are obtained in a dry or anhydrous form, by depriving them of their water of crystallization; An in is any in this particular, the process is similar to desiccation. (See No. 12.) Calcination is Acidstro-negative compound, capable of also employed for the ignition of silica, &c., combining in definite proportions with bases in order to render it more easily reducible to to form salts. Most of the liquid acids posfragments or powder. sess a sour taste, and redden litmus paper.

The operation of calcining is conducted on The acids have been variously classed by difthe small scale in platinum spoons or cruci- ferent writers, as into organic and inorganic; Lles, and heat applied by the flame of a spirit metallic and non-metallic; oxygen acids, hylamp, or other appropriate means. When drogen acids, and acids destitute of either of large quantities of matter are calcined, metal or earthenware crucibles and the heat of a furnace are employed. Charcoal is thus obtained from wood, bone-black from bones, &c. these elements; the names being applied according to the kingdom of nature, or class of bodies to which the radical belonged, or after the clement which was presumed to be the acidifying principle. Acids are in various When 4 parts water are suddenly mixed with forms; some are gaseous, as carbonic acid; 1 part sulphuric acid, the temperature of the some are liquid, as nitric and acetic acid; mixture rises to about 300° Fahr. Whilst 4 others are solid, as citric and oxalic acid; parts pounded ice mixed with 1 part acid, others again under peculiar conditions assume sinks the thermometer to some degrees below. more than one of these forms. Acids, which zero. Sulphuric acid boils and distills over at are soluble or liquid, are corrosive, and more 620° Fahr., and freezes at about 20° below or less poisonous when concentrated. They zero.

The salts formed by the union of change vegetable blues to red and neutralize sulphuric acid with a base are called SULthe effects of alkalies on vegetable blues and PHATES. yellows. Most of the acids are soluble in water in all proportions; they neutralize the alkalies, effervesce with the carbonates, and combine with the bases generally, forming compounds called salts. The methods for estimating the strength or neutralizing power of acids, as well as the strength of their so- 3855. Το Obtain Commercial Sulphuric Acid. This is commonly called oil of vitriol, and has a specific gravity not less than 1.840, nor more than 1.845. It was first obtained by the distillation of green vitriol (sulphate of iron), but it is now made by bringing the fumes of sulphurous acid (see No. lutions, will be found under ACIDIMETRY, No. 3865) into contact with those evolved from a 78. The names of the acids end either in mixture of nitre and oil of vitriol, so that the -icor-ous; the former being given to that con- former becomes oxidized at the expense of the taining the larger portion of the electro-nega- latter. This process is conducted in a series tive element, or oxygen, and the latter to of leaden chambers, having a little water on that containing the smaller quantity. As the floor, to absorb the acid, and so arranged sulphuric acid, an acid of sulphur, containing as to prevent the loss of gas. As soon as the 3 atoms of oxygen; sulphurous acid, another water is found to have acquired a specific sulphur acid, containing only 2 atoms of oxy- gravity of 1.350 to 1.450, it is drawn off, and gen. When a base forms more than 2 acid concentrated (see No. 8) in leaden boilers to compounds with oxygen, the Greek preposi- a density of 1.659 to 1.700; after which it is tion hypo is added to that containing the further concentrated in green glass or platinum smaller portion, as hyposulphuric and hypo- retorts until the specific gravity reaches 1.842 sulphurous acids. The prepositions per, hyper, to 1.844. When cold, the clear acid is put and the syllable oxy are also prefixed to the into carboys (large globular bottles of green names of acids when it is intended to denote glass) packed securely with straw in strong an increase of oxygen, as hypernitrous acid, wooden cases, the neck being left exposed perchloric acid, oxymuriatic acid, &c. The for convenience in obtaining the acid without prefix hydro to the name of an acid denotes unpacking. that the acid combination is with hydrogen, 3856. Anhydrous Sulphuric Acid. and not with oxygen. All the strong liquid Anhydrous or dry sulphuric acid is obtained acids should be kept in glass bottles, furnished by heating Nordhausen acid (see No. 3858) in with perfectly tight ground-glass stoppers; a glass retort connected with a well-cooled glass vessels should be used in measuring receiver. them, and they should be dispensed in stoppered vials. Fluoric acid must be kept in a bottle made of lead, silver, platinum, or pure gutta-percha, as it acts readily on glass. In the combination of acids with bases to form salts, distinctive terminations are employed to denote the kind of acid present. The name of a salt of an acid ending in -ic, terminates in It is also prepared in the following manner: 2 parts strongest oil of vitriol are gradually added to 3 parts anhydrous phosphoric acid, contained in retort surrounded by a freezing mixture; when the compound has become brown, the retort is removed from the freezing bath and connected with a receiver which takes its place in the freezing mixture; a -ate; thus, sulphate of soda, formed from sul- gentle heat is applied to the retort, when phuric acid and soda. The name of a salt of white vapors pass over and condense in the an acid ending in -ous, terminates in -ite; as receiver under the form of beautiful silky sulphite of lime, formed from sulphurous acid crystals. The product equals in weight that and lime. The names of compounds formed of the phosphorus originally employed. The by the union of non-metallic elements, and addition of a few drops of water to these certain other bodies, with the metals or with crystals produces a dangerous explosion. each other, terminate in -ide or-uret; thus, They deliquesce rapidly and fume in the air; sulphide or sulphuret of silver, formed of sil- introduced into water, they hiss like red-hot ver and sulphur. (Cooley.) In accordance iron. They melt at 66° Fahr., and boil at with the scope of this work it has been found about 1050°, and do not redden dry litmus advisable to omit a number of acids, both paper. simple and compound, of limited practical