Oxygen is one of the most widely diffused of the elementary substances. It is a gaseous body. "Stand in awe and sin not: commune with your own heart upon your bed and be still"—Psalm iv. Because as they breathe more rapidly, the combustion of the carbon in the blood is increased by the oxygen inhaled, and greater heat is developed. Because it receives, with every current of air, a fresh supply of oxygen, which unites with the carbon and hydrogen of the coals, causing more rapid combustion and increased heat. Because oxygen, by itself, is incombustible. The wick of a candle, which retains the slightest spark, being immersed in oxygen, will instantly burst into a brilliant flame; and even a piece of iron wire made red-hot, and dipped in oxygen, will burn rapidly and brilliantly. Oxygen, though non-combustible of itself, is the most powerful supporter of combustion. Because when we immerse a burning substance into a jar of oxygen, it immediately burns with intense brilliancy; but directly it is withdrawn from the oxygen, the intensity of the flame diminishes, and the oxygen which remains is unaffected. Because animals placed in any kind of gas, or in any combination of gases, where oxygen does not exist, die in a very short time. It is found in the air, mixed with nitrogen; in water combined with hydrogen; in the tissues of vegetables and animals; in our blood; and in various compounds called, from the presence of oxygen, oxides. Because oxygen in any greater proportion than that in which it is found in the atmosphere, would be too exciting to the animal "As vinegar is to the teeth, and as smoke to the eyes, so is the sluggard to him that sent him."—Proverbs x. Nitrogen is an elementary body in the form of gas. It is chiefly found in the air, of which it constitutes 79 out of 100 volumes. It may be mixed with oxygen in various proportions; but in the atmosphere it is uniformly diffused. It is found in most animal matter, except fat and bone. It is not a constituent of the vegetable acids, but it is found in most of the vegetable alkalies. Acids are a numerous class of chemical bodies. They are generally sour. Usually (though there are exceptions) they have a great affinity for water, and are easily soluble therein; they unite readily with most alkalies, and with the various oxides. All acids are compounds of two or more substances. Acids are found in all the kingdoms of nature. Alkalies are a numerous class of substances that have a great affinity for, and readily combine with, acids, forming salts. They exercise peculiar influence upon vegetable colours, turning blues green, and yellows reddish brown. But they will restore the colours of vegetable blues which have been reddened by acids; and, on the other hand, the acids restore vegetable colours that have been altered by the alkalies. Alkalies are found in all the kingdoms of nature. No; they would immediately die. But a mixture of oxygen and nitrogen, in equal volumes, constitutes nitrous oxide, which gives a pleasurable excitement to those who inhale it, causing them to be merry, almost to insanity; it has, therefore, been called laughing gas. Because it introduces into the body more oxygen than can be consumed. It, therefore, deranges the nervous system, and being "Lord, make me know mine end, and the measure of my days, that I may know how frail I am."—Psalm xxxix. The mean quantity of the gases contained in the human blood has been found to be equal to 1-10th of its whole volume. In venous blood, the average quantity of carbonic acid is about 1-18th, that of oxygen about 1-85th, and that of nitrogen about 1-100th of the volume of the blood. In arterial blood their quantities have been found to be carbonic acid about 1-14th, oxygen about 1-38th, and nitrogen about 1-72nd. Such a supposition is highly improbable. It is probably derived from nitrogenised food, just as carbonic acid is derived from carbonised food. Venous blood is that which is returning through the veins of the body from the organs to which it has been circulated. Arterial blood is that which is flowing from the heart through the arteries to nourish the parts where those arteries are distributed. Venous blood contains more carbonic acid, and less oxygen and nitrogen than arterial blood. It will not burn, nor will it support combustion. Oxygen gas will not burn of itself, but it aids the decomposition by fire of bodies that are combustible. It is therefore called a supporter of combustion. But hydrogen gas, though it burns of itself "As coals are to burning coals, and wood to fire; so is a contentious man to kindle strife."—Proverbs xxvi. It is thrown off with the breath, mixed with carbonic acid gas, and flies away to be renewed by a fresh supply of oxygen. In the atmosphere. Nitrogen is said to possess a remarkable tendency to mix with oxygen, without having a positive chemical affinity for it. That is to say, neither the oxygen nor the nitrogen undergoes any change by the union, except that of admixture. The oxygen and the nitrogen still possess their own peculiar properties. Oxygen and nitrogen are found in nearly the same proportions in all climates, and at all altitudes. Yes. Usually hydrogen is present, which in burning unites with oxygen, and forms water. |