Chlorine is more powerful in its affinities than either Bromine or Iodine. The salts formed by these three elements are closely analogous in composition and often in properties. Those of the Alkalies, Alkaline Earths, and many of the Metals, are soluble in water; but the Silver salts are insoluble; the Lead salts sparingly so. The combinations of Chlorine, Bromine, Iodine, and Fluorine, with Hydrogen, are acids, and neutralize Alkalies in the usual, manner, with formation of Alkaline Chloride and water (see page 311). The test by which the presence of Chlorine is detected, either free or in combination with bases, is _Nitrate of Silver_; it gives a white curdy precipitate of Chloride of Silver, insoluble in Nitric Acid, but soluble in Ammonia. The solution of Nitrate of Silver employed as the test must not contain Iodide of Silver, as this compound is precipitated by dilution. CHLORIDE OF AMMONIUM. Symbol, NH{4}Cl. Atomic weight, 54. This salt, also known as Muriate or Hydrochlorate of Ammonia, occurs in commerce in the form of colourless and translucent masses, which are procured by _sublimation_, the dry salt being volatile when strongly heated. It dissolves in an equal weight of boiling, or in three parts of cold water. It contains more Chlorine in proportion to the weight used than Chloride of Sodium, the atomic weights of the two being as 54 to 60. CHLORIDE OF BARIUM. Symbol, BaCl + 2 HO. Atomic weight, 123. Barium is a metallic element very closely allied to Calcium, the elementary basis of Lime. The Chloride of Barium is commonly employed as a test for Sulphuric Acid, with which it forms an insoluble precipitate of Sulphate of Baryta. It is also said to affect the colour of the Photographic image when used in preparing Positive paper, which may possibly be due to a chemical combination of Baryta with Albumen; but it must be remembered that this Chloride, from its high atomic weight, contains less Chlorine than the alkaline Chlorides (see page 124). _Properties of Chloride of Barium._--Chloride of Barium occurs in the form of white crystals, soluble in about two parts of water, at common temperature. These crystals contain two atoms of water of crystallization, which are expelled at 212°, leaving the anhydrous Chloride. CHLORIDE OF GOLD. See Gold, Chloride of. CHLORIDE OF SODIUM. Symbol, NaCl. Atomic weight, 60. Common Salt exists abundantly in nature, both in the form of solid rock-salt and dissolved in the waters of the ocean. Properties of the pure Salt.--Fusible without decomposition at low redness, but sublimes at higher temperatures; the melted salt concretes into a hard white mass on cooling. Nearly insoluble in absolute alcohol, but dissolves in minute quantity in rectified spirit. Soluble in three parts of water, both hot and cold. Crystallizes in cubes, which are anhydrous.