OXYGEN AND BROMINE.

Unlike chlorine, bromine appears to form no stable compounds with oxygen; the following acids, however, show a similarity between the oxygen compounds of these two halogen elements:

Preparation. This compound is prepared by agitating a mixture of mercuric oxide, water, and bromine, when the following reaction takes place:

By successive additions of bromine and mercuric oxide, a solution may be obtained containing 6.2 per cent. of the acid. This solution decomposes under ordinary circumstances on heating, but in a vacuum it may be distilled unchanged at 40°.

Properties. The aqueous acid has a yellow color, and is an active oxidizing and bleaching agent.

The calcium salt of hypobromous acid has been prepared by adding bromine to calcium hydrate. Very little, however, is known of it, except that it resembles the corresponding salt of chlorine in its action.

BROMIC ACID, HBrO.

Preparation. Bromic acid is prepared by first obtaining a bromate from bromine and a hydrate :

3Br2+ 6KOH =5KBr+ KBrO3 + 3H2O.

Bromine.

Potassium
Hydrate.

Potassium
Bromide.

Potassium
Bromate.

Water.

The bromate being less soluble than the bromide is easily separated from it by crystallization.

The bromate is then decomposed by acid. As most potassium salts are soluble, it is preferable to take a base which forms an insoluble compound with some mineral acid; for this purpose silver and barium bromate have been recommended. The latter salt is cheap and easily decomposed by sulphuric acid, as follows:

It requires some care to add the exact amount of sulphuric acid necessary to precipitate all the barium, and when this is accomplished the acid solution is decanted from the insoluble barium sulphate.

Properties. The nearly colorless acid solution cannot be concentrated by heat, since it decomposes at 100° into bromine and oxygen; but by evaporating at ordinary temperatures in a vacuum over sulphuric acid it

may be reduced to a strength corresponding to the formula HBrO3.7H2O. Further concentration even at ordinary temperatures causes decomposition. In many of its properties it closely resembles chloric acid.

The bromates are generally soluble in water, and are decomposed on heating. Some give off oxygen with formation of bromides, while others evolve both bromine and oxygen, leaving an oxide of the metal.

Perbromic acid, HBrO, is said to have been discovered, but subsequent investigators have failed to confirm this.

OXYGEN AND IODINE.

One oxide and two acids of these elements are known, as follows:

Oxide.

Iodine pentoxide, IO.

Acids.

Iodic acid, HIO,
Periodic acid, HIO.

IODINE PENTOXIDE, 1205.

Preparation. One part of iodine is heated with ten parts of pure concentrated nitric acid until complete solution takes place and there are no more fumes evolved. On evaporating until a temperature of 200° is attained, all the nitric acid is removed and a white residue remains. The reaction may be best expressed in two stages, as follows:

Properties.-Iodine pentoxide is a white, crystalline powder, having a specific gravity of 4.487. On heating to 300° it is decomposed into iodine and oxygen. It is very soluble in water, and, when dissolved in an amount to form a syrupy liquid, the solution on standing deposits crystals of iodic acid.

IODIC ACID, HIO.

Preparation. The simplest method of preparation is by dissolving the above oxide in water:

I2O+ H2O = 2HIO3.

It may also be prepared from barium iodate and sulphuric acid. The iodate is made by dissolving powdered iodine in hot concentrated solution of potassium chlorate, and adding a few drops of nitric acid. After the evolution of chlorine has ceased and the solution has become cool, crystals of potassium iodate separate out. On dissolving this salt in water and adding barium chloride, barium iodate separates out as a white solid. This is then decomposed by the careful addition of sulphuric acid. The three reactions take place as follows:

Iodic acid is also formed when chlorine is passed into water in which finely-powdered iodine is suspended:

The hydrochloric acid is removed by moist, freshly-precipitated silver oxide.

Properties.-Iodic acid occurs in the form of colorless, rhombic crystals, having a specific gravity of 4.629 at o°. It is very soluble in water, but insoluble in alcohol. On heating to 170° the acid decomposes into iodine pentoxide and water. Organic matter, phosphorus, and sulphur inflame on coming into contact with the acid. Sulphurous oxide, sulphuretted hydrogen, and hydriodic acid decompose it with liberation of iodine:

The iodates are mostly soluble in water. On heating, some of them decompose into oxygen and an iodide, while others give off both oxygen and iodine, a metallic oxide remaining. The iodates are detected by adding to the solution a small quantity of sulphurous acid or a sulphate, to liberate iodine, and then a dilute solution of starch, with which the latter forms a blue color.

PERIODIC ACID, HIO.

Preparation. This acid is only known in the free state with two molecules of water. It is obtained most readily by acting on perchloric acid with iodine:

Properties. This compound consists of colorless, transparent crystals, which are deliquescent and readily soluble in water. They melt at 133° to 140°, and on the further increase of heat are decomposed into iodine pentoxide, water, and oxygen.

SULPHUR.

Symbol, S. Atomic Weight, 31.98. Sulphur was known to the ancients.

Valence, II.

Occurrence. It occurs in the free state, mixed with earthy matter, in the vicinity of extinct as well as active volcanoes. Its existence in the free state is supposed to be due to the sulphur dioxide and hydrogen sulphide in volcanic gases, which, reacting on each other, form sulphur, as follows:

In combination sulphur is found, as sulphide, combined with iron, lead, zinc, copper, mercury, and some other metals in smaller amount; as sulphate, combined with calcium in gypsum, with barium in heavy spar, with magnesium in kieserite, and with sodium and potassium. Sulphur also exists in the vegetable and animal kingdoms, combined in various organic compounds, and in some mineral waters as hydrogen sulphide.

Source. The principal source of sulphur has always been the volcanic districts in the island of Sicily and the other volcanic regions that border the Mediterranean.

In recent years very large deposits have been found in the United States. A large mine is worked near Santa Barbara, in California. Two hundred miles south of Salt Lake City, at Cove Springs, Utah, a deposit of sulphur exists two thousand feet square and of unknown depth; shafts have been sunk to the depth of sixty feet without reaching the bottom. This sulphur is free from antimony and arsenic. The annual output in Utah and Nevada amounts to several thousand tons. The cost of transportation is the greatest obstacle to our obtaining all our sulphur from these sources. The exportation from Sicily amounts to about 200,000 tons annually. In 1892 the United States consumed 100,721 tons of Sicilian sulphur and 1825 tons of the American product. In addition to this, there were used 210,000 tons of imported pyrites, containing 43 per cent. of sulphur, and 119,000 tons of American pyrites, containing 44 per cent. of sulphur.

In addition to the above sources, sulphur is found in Iceland, Mexico, Central America, and the Sandwich Islands. Volcanoes in all these places either are or have been the cause of the deposit. In Mexico the sulphur is hoisted in buckets from the crater of Popocatapetl.

Extraction and Purification.-The sulphur earth and masses of ore are piled, with a small amount of fuel, in heaps over depressions in the earth. The heaps are then ignited; the sulphur melts, runs down, and is collected from the hollow beneath.

Only about one-third of the sulphur is saved by this means, the other two-thirds being consumed in heating. This process has been modified from time to time, so as to decrease the loss. One of these modifications, shown in Fig 51, consists of a furnace of mason-work, with an inclined bottom. When the ore is filled in, a number of channels are left to assist in the distribution

of the heat, and over the top of all is placed a layer of powdered ore and then a layer of the burnt ore. The pile is then ignited at the bottom of the furnace, and the sulphur running down the inclined bottom is removed at the mouth. The principal advantages of this process arise from the increased size of the furnace and the closed bottom, which enables one to control the operation, so that less sulphur is burned. Some of these furnaces are as much as 10 meters in diameter, and several weeks are required to complete one charge. The richest ores, containing 30 to 40 per cent. of sulphur, yield as much as 25 per cent., and the poorer ones, containing 20 to 25 per cent., yield 10 to 15 per

cent.