Chemical change

“ In the phenomena of light, with a spectroscope, a luminous gas is sympathetic with, and emits and absorbs, only particular kinds of luminous rays. In chemical action also, combustion excites combustion, ferment excites ferment, infection communicates infection, and the similar chemical change is transmitted from molecule to molecule. ”

“ We know that, floating around us, these volatilized bodies exist in some material form, and numerous experiments in chemistry are calculated to convince us, that the most attenuated air is capable, with a slight change of circumstances, of being converted into the condition of solid masses. Hydrogen gas, the lightest, the most ethereal of the chemical elements, dissolves iron and zinc, arsenic, sulphur, and carbon; and from the transparent combinations thus formed, we can with facility separate those ponderous bodies. Such substances must exist in our own atmosphere ”

“ Hence, as putrefaction is impossible in the absence of moisture, and the active agent, albumen, equally reduced, decomposition of such substances that remain ensues only by a process of decay, slow combustion or oxidation, the slowly uniting of oxygen with the substance. In this the constituent parts of the animal tissues break up into simpler compounds by the chemical changes that nature produces, and differs from other forms of putrefaction only by the length of time employed. ”

“ Decomposition of organic matter by bacteria. When living matter dies and undergoes decay complicated chemical reactions take place, one result of which is that the nitrogen of the organic matter is set free either as the element nitrogen, or in the form of simple compounds, such as ammonia (NH3) or oxides of nitrogen. Experiment has shown that all such processes of decay are due to the action of different kinds of bacteria, each particular kind effecting a different change. ”

“ As in general we very often involuntarily confuse chemical processes with physical, it may be that a physical process of change in the coefficient of expansion with a change of temperature participates with a change in molecular weight, and partially, if not wholly, accounts for the decrease of the density of chlorine, bromine, and iodine. ”

“ When this element, nitrogen, is combined with the wonderful variety of compounds formed by carbon, we have not only a great many intimately related yet distinct [100] substances, but compounds which readily change from one form to another. These are the distinctive qualities or conditions necessary, from a chemical standpoint, to make the processes of life possible. Protoplasm, which is the basis of all life, is formed by an intimate mixture of a number of complex chemical compounds, the chief elements of which are carbon, hydrogen, oxygen, and nitrogen. ”

“ It is evident, therefore, that in such circumstances there must be a very slow and long-continued chemical action, partly owing to the slow penetration of the mass of lime by the external carbonic acid, partly to the change going on in the remains of animal matter, at all events as long as any is left. ”

“ Living processes such as photosynthesis involve very specific changes in molecules and atoms; they are carried out by large, complex molecules that have very particular chemical properties allowing them to 'direct' change in their chemical environment that would not normally happen. ”

“ Such an arrangement, if erected upon a scale sufficiently extensive, with the medium of a neutro-saline solution, would, in his opinion, produce large quantities of acids and alkalies with very little trouble or expense.
249 Alterations in chemical equilibrium are constantly taking place in Nature, and he thinks it probable that the electric influence, in its faculties of decomposition and transference, may considerably interfere with the chemical changes occurring in different parts of our system. ”

“ Physical Changes separate Molecules from each other, while Chemical Changes destroy and break up the Molecule, so that its identity is forever lost, its Atoms thereafter either existing free from combinations, or else recombining with other Atoms, and forming new combinations. Chemical changes are occasioned by either physical or chemical agencies. The physical agencies generally employed are heat, electricity, light, pressure, percussion, etc. ”

“ Hence, reactions between organic compounds, even when they are in solution, proceed very slowly unless carried on at high temperatures, under increased pressure, or under the influence of some catalytic agent. Even under the stimulation of these reaction-accelerating agencies, most chemical changes in organic compounds when carried on in the laboratory, require several hours or even days and sometimes weeks, for their completion. But when similar reactions take place in living organisms, they proceed with velocities which resemble those of inorganic compounds in the laboratory. ”

“ To destroy organic matter the most powerful oxidizing agents are required. We must boil it with nitric acid and chloric acid and the most perfect chemical agents. To think to get rid of organic matter by exposure to the air for a short time is absurd. ”

“ In addition to the sources of pollution of the atmosphere which we have been considering, there are various trades and manufactures in which poisonous matters are given off. Some of these are of an organic nature, as in the melting of fats, in the making of size and glue, in the boiling of oil, in the boiling of bones, and in many other processes carried out on a considerable scale, where the emanations are highly offensive and often of unknown chemical composition. ”

“ When oxygen combines with a single element, what is the compound called? We have found that O makes up a certain portion of the air; later, we shall see how large the proportion is. Its tendency to combine with almost everything is a reason for the decay, rust, and oxidation of so many substances, and for conflagrations, great and small. New compounds are thusformed, of which O constitutes one factor. Water, H2O, is only a chemical union of O and H. Iron rust, Fe2O3 and H2O, is composed of O, Fe, and water. The burning of wood or of coal gives rise to carbon dioxide, CO2, and water. ”

“ May we not, therefore, conclude that the chemical action exhibited in a burning body is a development of some latent force, with which we are unacquainted, produced by the absorption of light;—that a repulsive action at first takes place, by which the hydrogen and carbon are separated from each other;—and that in the nascent state they are seized by the oxygen, and again compelled, though in the new forms of water and carbonic acid, to resume their chains of combining affinity? ”

“ They absorb oxygen from the surrounding medium, air or water, and, in addition to certain inorganic substances, take into their bodies, as their proper nutritive material, complicated protein compounds, which they derive either directly or indirectly from plants. Through the oxidation of these compounds they form substances of a simpler chemical structure, such as carbonic acid, water, and ammonia, and discharge these through their bodies as waste. ”

“ When the body of a man, or of an animal, is exposed to the combined influences of air, of water, and of a moderately high temperature, it undergoes a series of chemical decompositions, whose final term is its transformation into carbonic acid gas, and some compounds, gaseous or solid, which represent the less advanced products of destruction. Gases of various kinds, carbonic acid, hydrosulphuric, and ammoniac, and the vapour of water, spread themselves through the atmosphere, or dissolve into the humidity of the soil. ”

“ The peculiar manner in which hydrogen gas appears to dissolve solid substances,—as iron, potassium, sodium, sulphur, phosphorus, selenium, and arsenic, may be explained by regarding the results as a manifestation of the powers of chemical affinity over the forms of bodies. In like manner, the solution of salt in water, or the mixture of alcohol in that fluid, may be viewed as chemical phenomena, although usually considered as simple cases of solution or mixture: alterations of temperature and other physical changes taking place in either. ”

“ The vegetable matter has lost the principle of organic life, and, that gone, the tendency of all things being to be resolved into their most simple forms, a disunion of the elements commences: oxygen, hydrogen, and carbon pass off either in the gaseous state or as water, whilst some carbon is liberated in a very finely-divided condition, and enters slowly into combination with oxygen supplied by the water or the air. Hydrogenous compounds are at the same time formed, and, under all these circumstances, as in all other chemical phenomena, an alteration of temperature results. ”

“ Thus we find 'inflammable air* as the name for hydrogen, 'fixed air* for carbonic acid gas, and 'dephlogisticated marine acid air' for chlorin. That no better principle of classification of substances from a chemical standpoint than that of superficial outward appearance was demanded is not strange, when we recollect that at this period and, indeed, down to the close of the eighteenth century, the transmutation of metals was a popular belief of the common people and was not disproved by the chemist. ”

“ As the result of laboratory experiments designed to show the effect of the violent escape of vapour produced below the surface of molten metal in causing contamination of the air, and the nature of the contaminating substances, he was able to conclude that the chemical action of the materials (acid and flux) used, and subsequent vaporization of the products of this action, was a much more important factor than the mechanical action of escaping vapour. ”

“ It brings home to me what an unstable chemical compound man is. Here are the stage accessories as good as ever, while the players have all split up into hydrogen and oxygen and nitrogen and carbon, with traces of iron and silica and phosphorus. ”

“ The putrefaction of animal and other azotized bodies is a chemical process, by which they are gradually dissipated in a gaseous form, chiefly in that of carbonic acid and ammonia; now to convert the carbon of the animal substance into carbonic acid requires oxygen, and to convert the azote into ammonia requires hydrogen, which are the elements of water. ”

“ The chemical agencies discussed were the following: sulphurous and sulphuric acids, discharged in vast quantities into the air of the city, by the combustion of coal and gas, the decomposition of street refuse and sewer gas, etc.; carbonic, nitric, and hydrochloric acids; carbolic, hippuric, and many other organic acids derived from smoke, street dust, sewer vapors, etc.; oxygen and ozone, ammonia, and sea salt.
The mechanical and physical agencies discussed were the following: frost; extreme variations in temperature, amounting in our climate to 120° F. in a year, and even 70° in a single day ”

“ It was formerly supposed that the substances found in plants and animals, mostly complex compounds of carbon, hydrogen and oxygen, could only be produced by "vital forces." If this were true it meant that chemistry was limited to the mineral kingdom and to the extraction of such carbon compounds as happened to exist ready formed in the vegetable and animal kingdoms. But fortunately this barrier to human achievement proved purely illusory. The organic field, once man had broken into it, proved easier to work in than the inorganic. ”

“ What the 'vital principle' may be, neither chemists nor physiologists can tell us with any great degree of clearness; but it is this vital principle, whatever it may be, which prevents decay in a living organic substance, however complex. When life departs, the onslaught begins; the defender has been removed, and a number of assailants make their appearance. Air, heat, and moisture are the principal of these; they attack the dead organism, and gradually convert it into wholly different and inorganic compounds, such as water, carbonic acid, ammonia, phosphuretted hydrogen, and many others. ”

“ In other words, "How can the ferments which are living beings, and which contain materials of the same order as those of all living beings, decompose after the decompositions which they have themselves provoked? How can they be destroyed and disappear, or at least be reduced to the germs alone, which are eternal, so much at least as life may be eternal on the surface of the earth? How can the materials which compose them become gaseous and return to the atmosphere in the more or less mineral forms of vapor, carbonic-acid gas, hydrogen, nitrogen, ammonia, etc.?" ”

“ These properties are further causes of instability, inasmuch as they expose the organic substances to a number of disturbing influences. Thus, organic matter is not only subject to decomposition by light and heat, but also by the direct or indirect chemical action of bodies entering it, or acting on it from without. ”

“ Where two elements combine to form a compound, heat is almost always evolved, and the amount evolved serves as a measure of the affinity. In order that chemical affinity may come into play it is necessary that the substances should be in contact, and usually one of them at least is a fluid or a gas. The results produced by chemical combination are endlessly varied. Colour, taste, and smell are changed, destroyed, or created; harmless constituents produce strong poisons, strong poisons produce harmless compounds. ”

“ In passing through the city a continuous change for the worse takes place, which is manifested by the increase of oxidizable matter and of chlorine, and by a hundred-fold augmentation of ammonia and albuminoid ammonia. ”