and is absolutely necessary for the support of animal life a. What is the nature of oxygen gas, when in a separate state? Pure oxygen gas has the property of accelerating the circulation of all the animal fluids, and occasions the most rapid combustion of all combustible substances; so that it is the most energetic and powerful agent that we are acquainted with. What is the specific gravity of oxygen gas ? Oxygen gas is a little heavier than atmospheric air, and 740 times lighter than water. success in cases of suspended animation. See Additional Notes, No. 6 and 8. Water impregnated with oxygen gas has been found a valuable remedy in some particular diseases. By depriving common water of atmospheric air by boiling, and then forcing oxygen gas into it, I have occasioned a large absorption of it, and have found that it retained it better than carbonic acid gas is retained by water. Later experiments by Dr. Henry have determined that water takes up of its volume at 60° whatever be the density of the gas. a It has been proved by Mr. Hassenfratz, that oxygen is necessary to promote the vigour of plants as well as that of animals; and that, to this end, a much larger quantity of oxygen is combined with snow, and in rain water, than in river or spring water. "LEAVES, LUNGS, and GILLS, the vital ether breathe On earth's green surface, or the waves beneath." A collection of experiments on the effects of oxygen on animal and vegetable life may be seen in " Archer's Observations on Oxygen," Svo. 1798. See Additional Notes, No. 6. At the temperature of 54.50, when the barometer stands at 28 inches, oxygen gas is 12 drachms (or 11⁄2 ounce) to each cubical foot: whereas nitrogen gas is only 10 drachms 49 grains to the cubical foot. Oxygen gas is plentifully procured from nitre, or from the black oxide of manganese. Four ounces of nitre melted with a little slacked lime produced Mr. Ingenhousz 3000 cubic inches of vital air. See Additional Notes, No. 7. What are the principal properties of nitrogen gas? Nitrogen gas or azote is chiefly distinguished by certain negative qualities, such as its being incapable of supporting combustion and animal life. It is uninflammable and somewhat lighter than atmospheric air a. Seeing that nitrogen gas is injurious to animal life, what is the use of so large a quantity of it in atmospheric air? Nitrogen gas has the effect of neutralizing, in some measure, the properties of oxygen gas, and rendering it fit for respiration and combustion b. • From some late experiments it seems probable that nitrogen is not a simple substance. See Phil. Magazine, vol. xxxiii. page 173. Indeed the experiment of Dr. Priestley, by which he procured several portions of nitrogen from the same distilled water by repeatedly freezing it, seems to confirm this opinion. See Nicholson's Journal, quarto, vol. iv. page 137. But the novel experiments of Sir Humphry Davy are more to the purpose. From these it would appear that nitrogen is a compound of hydrogen and oxygen. See Phil. Trans. for 1809. Nitrogen was discovered by Dr. Rutherford in the year 1772. Nitrogen forms a part of all animal substances. It is also the base of ammonia, and of the nitric acid. It appears to be favourable to plants, as they grow and vegetate freely in this gas. It seems to be the substance which nature employs in converting vegetables to animal substances; and to be the grand agent in animalization. See Fourcroy's Philosophy of Chemistry, chap. xi. When nitrogen gas is required for experiments, it may be thus procured: --Take a few iron filings, mix them with a little sulphur, and moisten the mass with water. Put this mixture into a large glass jar, and cork it close. In a few days the oxygen will be absorbed by the mixture from the air which was previously in the glass, and the residuum will be found to be nitrogen gas. It may be procured also by digesting very dilute nitric acid with pieces of flesh, or on the muscular fibre. b According to Trousset, the gas emitted by the skin is pure nitrogen. Annales de Chimie, tom. xlv. 73. "If the proportion of oxygen and nitrogen were reversed in atmospheric air, the air taken in by respiration would be more How is this change effected by nitrogen gas? By the union of nitrogen gas with oxygen gas: the latter, which would burn every thing within its reach with an unparalleled activity, is, as it were, dissolved and diluted; and the nature of the former is so much enveloped by the latter, that the compound possesses properties different from either of these gases, so as to be fitted for every purpose for which it was designed ". How does atmospheric air support life. stimulant, the circulation would become accelerated, and all the secretions would be increased; but the tone of the vessels, thus stimulated to increased action, would be destroyed by over-excitement; and, if the supply from the stomach were not equal to the consumption, the body must inevitably waste and decay." -(Dr. Lambe.) Though nitrogen gas is, by itself, so noxious to animals, it answers an important end when mixed with oxygen gas in atmospheric air. Were it not for this large quantity of nitrogen in the atmosphere, the blood would flow with too great rapidity through the vessels, and all animals would have too great spirits; the consequence of which would be, that the life of man would not be protracted to the length that it now is. "From Nature's chain whatever link you strike, Tenth, or ten-thousandth, breaks the chain alike." Nitrogen gas has been medicinally administered with success in cases of increased irritability, such as inflammation, &c. See Fourcroy's General System of Chemical Knowledge. The necessity of atmospheric air, for the support of life, was exemplified by a melancholy accident which happened to two men in the bay of Dublin, who went to visit a wreck in a diving-bell. Two barrels of fresh air were to be alternately sent down to them, and the contaminated air was to be let out by a stopcock at the top of the bell. But by the contraction which ropes suffer in being wet, the bell turned round in its descent, and entangled the strings by which the divers meant to rng bells, and indicate their wants to the people on board the ship from whence they were lowered. Waiting too long for these signals, the bell was raised, and the divers were both found dead. They were not drowned, but died, like the unhappy people in the hole at Calcutta, for want of a supply of pure air. By giving out its oxygen and caloric to the blood a. What do you mean by caloric? Caloric is the name which modern chemists have given to fire, or the matter of heat; a large portion of which is intimately combined with atmospheric air b. a Dr. Priestley has shown, by a variety of experiments, that the blood perpetually receives oxygen gas (or what he calls dephlogisticated air) from the atmosphere, by the agency of the lungs. See his Experiments on Air. The blood is purple when it arrives at the lungs ; but having there thrown off hydrogen and charcoal, it imbibes the vital air of the atmosphere, which changes its dark colour to a brilliant red, rendering it the spur to the action of the heart and arteries; the source of animal heat; and the cause of sensibility, irritability, and motion."-Thornton's Philosophy of Medicine. Black venous blood, exposed to the air, becomes red on its surface; and air, remaining confined over venous blood, loses its oxygen, so that what remains is found to be unfit for combustion. These facts prove that the vermilion colour of the blood is owing to the inhalation of oxygen gas. "The internal surface of the lungs, or air vessels, in man, is said to be equal to the external surface of the whole body: it is on this extended surface that the blood is exposed, through the medium of a thin pellicle, to the influence of the respired air." See Additional Notes, No. 8. ""Tis surely GOD Whose unremitting energy pervades, Seems not to work with such perfection framed Is this complex stupendous scheme of things." THOMSON. By the rise of the breast-bone in man, and the descent of the diaphragın, room is afforded for 42 cubic inches of atmospheric air at every drawing in of the breath. A deeper inspiration will give room for more than twice this quantity. Keill's Anatomy. b This name was given by the framers of the new nomenclature to the matter of heat, which they always distinguish from the effect. Caloric is applied to fire, or the substance which produces the sensation we call heat, but never to the sensation itself, or the effect produced by fire. In this case it is said that caloric raises the temperature of bodies, or, on the contrary, that the temperature is lowered by the loss of caloric. Is the caloric which is combined with the air we breathe sufficient of itself to keep up the necessary heat of the body? Animal heat is preserved chiefly by the inspi ration of atmospheric air. The lungs, which imbibe the oxygen gas from the air, impart it to the blood; and the blood, in its circulation, gives out the caloric to every part of the body a. a Dr. Menzies ascertained that the blood in its passage through the lungs gains more than one degree of Fahrenheit's thermometer. Dr. Menzies on Respiration. Dr. Crawford instituted a series of experiments, with a view to discover the cause of animal heat. In the course of his inquiry, he found that blood contains a much greater quantity of absolute heat than the elementary substances of which it is composed, and that in its change from venous to arterial blood it acquires a greater capacity for caloric; by which admirable contrivance, any rise of temperature in the lungs which would be incompatible with life, is prevented. Nothing can afford a more striking proof of creative wisdom, than this provision for the preservation of an equable animal temperature. By the decomposition of atmospheric air, caloric is evolved, and this caloric is taken up by the arterial blood, without its temperature being at all raised by the addition. When it passes to the veins, its capacity for caloric is diminished, as much as it had before been increased, in the lungs : the caloric therefore, which had been absorbed, is again given out; and this slow and constant evolution of caloric in the extreme vessels over the whole body, is the source of that uniform temperature which we have so much occasion to admire. This same chemist has ascertained that whenever an animal is placed in a medium the temperature of which is considerably high, the usual change of arterial into venous blood does not go on; consequently, no evolution of caloric will take place, and the animal heat will not rise much above the natural standard. How pleasing is it to contemplate the arrangements which the Deity has made for the preservation and felicity of his creatures, and to observe that he has provided for every possible exigency! According to Lavoisier, a man generally consumes 32 ounces troy of oxygen gas in 24 hours; that is, the lungs separate this quantity of oxygen gas from the air which he respires in that time. The blood, in passing through the lungs to take up oxygen |