talloids for the oxygen, we shall have the subchloride, protochloride, bichloride, &c. When the metalloids unite, compounds are generally formed which have acid characters. The acid compound containing most oxygen has the terminaction in ic; as, sulphuric, nitric, chloric, phosphoric. The compound containing the next less quantity of oxygen terminates in ous; phosphorous, chlorous, sulphurous. When other compounds were discovered the prefixes hyper and hypo were introduced. Hypophosphorous acid Chlorous acid The prefix per is usually given to indicate the highest or most intense. In the case of metals it is given to the highest oxide destitute of acid properties. The nomenclature of a salt is derived from that of the acid. When the acid ends in ic the salt ends in ate-sulphate of lime. When it terminates in ous the salt ends in ite-nitrite of soda. Hyponitrate, hyposulphate, hyponitrite, hypophosphite, &c. Bisulphate, MO.2SO3, sesquisulphate 2MO. 3SO3. BASIC OXIDES. It has been stated that the metallic oxides are divided into bases, acids, and indifferent bodies. Several of the metals combine in different proportions with oxygen, and the chemical character of these compounds is determined in a great measure by the quantity of oxygen they contain. The oxides of manganese afford a good illustration. The protoxide, MnO, is a powerful base, the sesquioxide, Mn2O3, is feebly basic. The binoxide or peroxide, MnO2, is an indifferent body; while MnO3, manganic acid, and Mn2O7, permanganic acid, are acid bodies. Very few of the metals form acid oxides, or indifferent bodies; but the next oxide after an indifferent body, has acid properties. The most important basic oxides are the following. The symbols of these bases should be committed to memory. Most of these bases are insoluble in water: those which are soluble restore the blue colour of litmus, which has been reddened by an acid. Soda, potash, and ammonia are called alkalies: the latter is called the volatile alkali. These bodies are soluble in water, and neutralise the strongest acids. Baryta, strontia, lime, and magnesia, are called alkaline earths: except magnesia, they are all soluble in water, but less so than the alkalies. Alumina is insoluble in water, and belongs to the earths. It may appear strange that the terms protoxide of potassium, protoxide of sodium, protoxide of ammonium, are not applied instead of potash, soda, ammonia, baryta and lime. There can be no doubt but protoxide of potassium is the correct term for potash, but when these names were given they were considered simple bodies, and the terms potash, lime, still continue in use. In writing out simple chemical formula, figures frequently occur. A little figure to the right merely shows the number of equivalents of the element taken, which stands to the left of the figure. Carbonic oxide, CO, means one equiva lent of carbon and one of oxygen. Carbonic acid, CO2, means one equivalent of carbon and two of oxygen. Sesquioxide of iron, Fe,O,, means two equivalents of iron and three of oxygen. The binoxide of mercury, HgO,, means one equivalent of mercury and two of oxygen. The biniodide of mercury, HgI2, means one equivalent of mercury and two of iodine. The terchloride of gold, AuCl3, means one equivalent of gold and three of chlorine. The terhydride of arsenic, AsH,, means one equivalent of arsenic and three of hydrogen. Hydrides must not be confounded with hydrates. The former is a union of hydrogen with some other body; the latter is a union of water with some substance, as the hydrate of lime, CaO,HO. When compounds of the metalloid and metal are written symbolically, the metal is placed first. Chloride of calcium, CaCl. When the metalloids combine, the hydrogen is placed before the other metalloid, except in the case of phosphorus and carbon, CH. PH. ACID BODIES. An acid body was formerly defined as an oxidised compound which had a sour taste, turned blue litmus red, and neutralised alkalies. This definition is not sufficient because we know many compounds without oxygen that have all the properties of an hydrochloric acid, HCl, and some bodies, such as carbonic and boracic acid, cannot neutralise the alkaline reaction of potash. Chemists now regard as acids all those compounds which unite with potash and soda, and give rise to compounds similar in their composition and character to the salts which sulphuric, nitric, or some admitted acid forms when combined with these alkalies. The oxygen combinations with the metalloids form acids with very few exceptions. The hydrogen compounds of the metalloids are also chiefly acid. When oxygen acids combine with water, they are called hydrated acids, hydrated sulphuric acid, HO,SO3. When they are deprived of this water, they are anhydrous, SO, Acids are monobasic, bibasic, or tribasic, according as they unite with one, two, or three equivalents of base. All the acids in the following list are monobasic, except phosphoric, arsenic, and arsenious acid. |