OXYGEN, 0,=16 - OZONE, O3.

Oxygen is the most universally diffused element, forming part of the air, the water, the earth, and of the tissues of plants and animals. Of the air it constitutes 23.01 per cent. by weight, 20.81 per cent. by measure, being about one-fifth part. By Priestley, who discovered it (in 1774), it was named "dephlogisticated or vital air."

Ozone is an allotropic form of oxygen. Its discoverer, Schonbein, did not arrive at a knowledge of its real nature, but Odling (in 1860), by a "splendid hypothesis," concluded it to be a condensed condition of oxygen, and this was afterward verified, among other observers, by Bro-die, who adopted the symbol 03, implying that three atoms of oxygen are condensed in each one of ozone. A minute proportion of it is found in the atmosphere - more in that of the open country and of the sea than in that of towns, but its precise distribution and variation are not yet ascertained. Richardson calculated its amount as 1 in 10,000 of air ("British Association Report," 1865).

Preparation

Oxygen may be obtained pure from most of its combinations, but is conveniently and usually prepared by heating the peroxide of manganese, or the chlorate of potash, or both together. The former yields about one-ninth of its weight of oxygen. 3MnO2=MnO, Mn208 + 20; or 2KC103=2KCl+302.

Ozone is produced in small quantities during the slow oxidation of phosphorus and some other substances. Lender recommends for its evolution in sick chambers a mixture of peroxide of manganese, permanganate of potash, and oxalic acid, to be dissolved in water. In the laboratory it is prepared by passing a succession of electric sparks through a closed chamber filled with air.

Characters And Tests

The principal characteristic of oxygen is its energetic power of combination with organic principles, and with minerals, to form acids and salts (oxidation), and with hydrogen to form water. It is a gas devoid of color, odor, or taste, of sp. gr. 1.1057 (atmospheric air being taken as 1). Under a pressure of 320 atmospheres, and at a temperature of - 220° F., it has been liquefied by Pictet (1877).

Ozone is much denser than oxygen, and in most chemical and physical, though not in all vital effects, it is more active; it is further distinguished by a peculiar odor; also it is a powerful oxidizing agent, and changes many protosalts into persalts; it displaces iodine from some of its combinations, hence iodized starch paper is used as a test for the gas -the paper turns bluish as iodine is set free, and combiners with the starch, but the test is not very dependable. Ozone is absorbed by turpentine.

According to Paul Bert, it possesses marked antiseptic properties, and animal substances keep long unputrefied in an atmosphere to which a minute proportion of ozone has been added (Medical Record, 1876; Comptes Rendus, t. 80).

Physiological Action (External)

The external and local action of oxygen in contact with mucous membrane or denuded skin is moderately stimulating.

Physiological Action (Internal)

To describe fully the physiological action of oxygen would involve a description of the processes of respiration, sanguification, nutrition, and tissue-change, for to all these, and to life itself, it is essential. If it be deficient in the respired air, or if it be insufficiently absorbed, all the functions become disordered, assimilation is impeded, circulation diminished, and temperature lowered, and if its access to the lungs be prevented for a few minutes, life altogether ceases. But we are concerned, at present, only with the results of certain experiments in which animals or men have been made to respire either pure oxygen, or an atmosphere artificially charged with a definite proportion of the gas, and the first question that arises is whether more than a normal amount of oxygen can be taken into the blood under such circumstances.

It was early proved that animals kept under a bell-jar filled with oxygen lived longer than in ordinary air; and also that animals made to breathe oxygen could resist asphyxia longer than similar animals that had breathed only air (Priestley, Beddoes), but Regnault and Reiset, while corroborating the former observation, concluded, from a series of experiments, that breathing an atmosphere rich in oxygen, or even one of the pure gas, did not make the blood take up more oxygen than it would from ordinary air, nor was more carbonic acid excreted in consequence (Annales de Chimie, 1844). But these conclusions, which had much influence on professional opinion at the time, have been disproved. Preyer showed that a greater saturation from oxygen-inhalation is, a, priori, probable, and that ordinary arterial blood is not fully saturated with oxygen -that it can take up more by being shaken with the gas. Demarquay proved it by showing that suppurating, indolent, or unhealthy wounds on the extremities of animals became quickly florid and hyperaemic when pure oxygen was inhaled; an extra amount of the stimulating gas must clearly have been carried by the circulation to the wound. Allen and Pepys, and later, Limousin, showed, by inhaling an equal quantity of atmospheric air at one time, and of oxygen at another, that, after the latter, double the amount of carbonic acid was expired, and this increase continued fifteen minutes after the inhalation had finished. Other observers have reported that the elimination of uric acid during a course of oxygen-inhalation is markedly lessened, i.e., that more complete combustion occurs within the system (Schmidt's Jahrb., 1865, t. 1, s. 28); thus, Kollmann found that while 300 grammes of the ordinary secretion of urine contained 236 milligrammes of acid, the same quantity contained only 122 milligrammes after inhalation of 12 litres of oxygen. On another occasion the amount of acid came down from 134 milligrammes to 25 milligrammes.

A clinical illustration, pointing in the same direction, is given by Gubler. After several copious draughts of the pure gas in an active nascent condition, the respiratory movements and the pulse became slower, a general sense of comfort was felt, and, without any dyspnoea, the pause between expiration and inspiration could be much prolonged. Thus, taking thirty seconds as a maximum time during which the breath may be "held" after breathing atmospheric air, it rises to ninety to one hundred seconds after breathing oxygen. From other observations, Gubler concludes that the blood receives the gas in proportion to its physical capacity for it, rather than in proportion merely to the vital necessity of hae-matosis: the globules absorb what they need, while any excess circulates free, and enters into combination only as the haemoglobulin loses oxygen in passing through the capillaries. Hence, the amount of oxygen absorbed by an individual is proportionate to the number of his corpuscles (we should now say of his haemoglobin), and a plethoric man quickly using up his reserve air breathes faster than a healthy one. On the other hand, an anaemic patient also breathes more rapidly than normal, since his corpuscles are either too few in number or otherwise altered, so that they cannot take up enough oxygen.1 Buchheim states an opposite view, viz., that oxygen is not absorbed proportionally to the amount of it brought to the lungs, but to its requirement for tissue-change; yet even he admits that the amount taken in can be increased to some extent by continued deep inspirations, and by breathing air rich in oxygen or under high pressure; he only denies that such adventitious oxygen affects the tissue-change (Archiv fur Exper. Pathologie: Klebs, Bd. iv., 1875); he admits also that improvement in symptoms may result from breathing compressed air or pure oxygen, but thinks we cannot hope to influence the course of illness by increasing the amount of oxygen contained in the blood.

1 "Quinquaud, availing himself of the reducing properties of sodic hydrosulphite, was enabled to calculate the maximum quantity of oxygen capable of being absorbed by a given amount of blood. The mean capacity in health, he found, was 240 cubic centimetres of oxygen to every 1,000 grammes of blood = 128 grammes haemoglobin." He assumes that this absorption capacity is invariable, but in reality it varies according to illness, especially in forms of anaemia. (Coupland: Gulstonian Lectures, March, 1881).