Back Aa

Reason Why

Close

<h2>CHAPTER III.</h2> 25. What is oxygen? Oxygen is one of the most widely diffused of the elementary substances. It is a gaseous body. <hr class="bible-verse" /> "Stand in awe and sin not: commune with your own heart upon your bed and be still"—Psalm iv. <hr class="bible-verse" /> 26. Why do persons who are walking, or riding upon horseback feel warmer than when they are sitting still? [Pg 32] 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. 27. Why does the fire burn more brightly when blown by a bellows? 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. 28. Why does not the oxygen of the air sometimes take fire? 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. 29. Why do we know that oxygen will not burn of itself? 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we immerse a burning substance into a jar of oxygen, it immediately burns with intense brilliancy; but directly it is withdrawn from the oxygen, the intensity of the flame diminishes, and the oxygen which remains is unaffected. 30. Why do we know that oxygen is necessary to our existence? 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. 31. Where is oxygen found? 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. 32. Why is the oxygen of the air mixed so largely with nitrogen? Because oxygen in any greater proportion than that in which it is found in the atmosphere, would be too exciting to the animal [Pg 33] system. Animals placed in pure oxygen die in great agony from fever and excitement, amounting to madness. <hr class="bible-verse" /> "As vinegar is to the teeth, and as smoke to the eyes, so is the sluggard to him that sent him."—Proverbs x. <hr class="bible-verse" /> 33. What is nitrogen? Nitrogen is an elementary body in the form of gas. 34. Where is nitrogen found? 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. 35. What are acids? 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. 36. What are alkalies? 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. 37. Could animals live in nitrogen? 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. 38. Why does nitrous oxide produce this effect? Because it introduces into the body more oxygen than can be consumed. It, therefore, deranges the nervous system, and being [Pg 34] a powerful stimulant, gives an unnatural activity to the nervous centres and the brain. <hr class="bible-verse" /> "Lord, make me know mine end, and the measure of my days, that I may know how frail I am."—Psalm xxxix. <hr class="bible-verse" /> 39. In what proportions are the atmospheric gases found in the blood? 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. 40. Then is nitrogen taken into the blood from the air? Such a supposition is highly improbable. It is probably derived from nitrogenised food, just as carbonic acid is derived from carbonised food. 41. What is venous blood? Venous blood is that which is returning through the veins of the body from the organs to which it has been circulated. 42. What is arterial blood? Arterial blood is that which is flowing from the heart through the arteries to nourish the parts where those arteries are distributed. 43. What is the difference between venous and arterial blood? Venous blood contains more carbonic acid, and less oxygen and nitrogen than arterial blood. 44. Will nitrogen burn? It will not burn, nor will it support combustion. 45. What is the difference between "burning" and "supporting 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 [Pg 35] will extinguish a flame immersed in it. It is therefore said to be a body which will burn, but will not support combustion. <hr class="bible-verse" /> "As coals are to burning coals, and wood to fire; so is a contentious man to kindle strife."—Proverbs xxvi. <hr class="bible-verse" /> 46. What becomes of the nitrogen that is inhaled with the air? It is thrown off with the breath, mixed with carbonic acid gas, and flies away to be renewed by a fresh supply of oxygen. 47. Where does nitrogen find 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. 48. In combustion does any other result take place besides the union of oxygen and carbon forming carbonic acid gas? Yes. Usually hydrogen is present, which in burning unites with oxygen, and forms water. <hr class="chap" /> <div style="break-after:column;"></div>

1 of 2

2 of 2