Hydrogen - Hydrogen is found in nature very widely distributed and in large quantities. It forms one-ninth of the weight of water, and is contained in all the principal substances which enter into the composition of plants and animals. It may be obtained by decomposition of water by means of the electric current, or by the action of substances known as acids on metals. The latter method is more commonly used in the laboratory. Acids contain hydrogen, give it off easily, and take up other elements in its place. Among the common acids found in every laboratory are hydrochloric, sulfuric, and nitric.

Distribution and production of hydrogen.

Pure hydrogen is a colorless, odorless, tasteless gas. It is not poisonous, and may therefore be inhaled without harm. It is the lightest known substance, being about 14.4 times lighter than air, 16 times lighter than oxygen, and 11,000 times lighter than water.

Hydrogen does not unite with oxygen at ordinary temperatures, but, like wood and most other fuel substances, needs to be heated up to the kindling temperature before it will burn. Hydrogen burns if a lighted match be applied to it. The flame is colorless, or very slightly blue.

Physical properties of hydrogen.

Chemical properties of hydrogen.

Water - Water is a compound and not an element, as can be shown by passing an electric current through it. If the ends of two wires, each connected with an electric battery, be put a short distance apart, in acidulated water, it will be noticed that bubbles of gas rise from each wire. As these gases cannot come from, or through the wires, they must be formed from the water. If they be analyzed, we will find that oxygen gas comes from one wire and hydrogen from the other.

This experiment shows that when an electric current is passed through water, hydrogen and oxygen are obtained, and also that there is obtained twice as much hydrogen as oxygen by volume. This proves that water is not an element, but a compound of two atoms of hydrogen and one of oxygen. The chemist therefore writes the symbol for water H2O.

Decomposition of water.

Proportion of hydrogen and oxygen in water.

We have just learned that with electricity we could decompose the compound water into its elements, hydrogen and oxygen. Now we can prove by another experiment that water contains these two elements. If we burn hydrogen gas, or any substance containing hydrogen, water is formed. This can be illustrated by inverting a cool, dry tumbler over a gas flame, which is composed chiefly of hydrogen, and water vapor will collect on the inside.

Though water is widely distributed over the earth, we never find it absolutely pure in nature. All natural waters contain foreign substances in solution. These substances are taken up from the air, or from the earth. Pure water is colorless, tasteless, and odorless.

Properties of water.

On cooling, water contracts until it reaches the temperature of 4° Centigrade (39° Fahrenheit). When cooled from 4° to 0° C. it expands, and the specific gravity, or weight compared with the space occupied by ice, is somewhat less than that of water; hence ice floats.

The purest water found in nature is rain-water, particularly that which falls after it has rained for some time; that which first falls always contains impurities from the air. As soon as rain-water comes in contact with the earth and begins its course toward the sea, it also begins to take up various substances according to the character of the soil with which it comes in contact. Mountain streams which flow over rocky beds, particularly beds of sandstone, contain very pure water. Streams which flow over limestone dissolve some of the stone, and the water becomes "hard."

Why ice floats.

Rain-water.

Hard water.

The many varieties of mineral water from the various springs throughout the country, take their properties from soluble substances with which they come in contact. Common salt is deposited in large quantities in different parts of the earth. Since salt is readily soluble in water, many streams pick up large quantities of it, and as all water courses ultimately find their way to the ocean, the latter becomes a repository for salt with which the earth-water is laden.

Effervescent waters all contain some gas, usually carbonic acid gas in solution, and they merely give up or set free a part of it when placed in open vessels.

Sulfur water contains a compound of hydrogen and sulfur, called hydrogen sulfid or sulfureted hydrogen, which we will refer to in its order later in this lesson.

Mineral water.

Salt water.

Effervescent waters.

Sulfur water.

Water may be purified by means of distillation. This consists in boiling the water and condensing the vapor by passing it through a tube which is kept cool by surrounding it with cold water. By means of distillation most substances in solution in water can be eliminated. Substances, however, which evaporate like water, will, of course, pass off with the water vapor. Aboard ship salt water is distilled and thus made fit for drinking. In chemical laboratories ordinary water is distilled in order to purify it for chemical work.