Flux (chemistry)

“ Fluxes.—These are for the purpose of regulating the temperature of fusion of a mixing—frit—some being better adapted for this purpose than others. This, however, is not the only consideration, for the character of the flux depends upon the composition or chemical changes to which the ingredients are to be subjected. The fluxes are borax, clays, cullet, porcelain, feldspar, gypsum, and fluorspar.
Glass.—Glass is composed of lime, silicic acid, and soda or potash. The use of the glass is to form the hard, crystal-like foundation. ”

“ The older workers could not define phlogiston; we are able to define energy, and therefore we can see clearly where they saw but darkly. Chemistry now acknowledges that the properties of a compound are not only determined by the composition of the matter of that compound, but by the amount of energy associated with that collocation of matter. ”

“ The law governing physical or heterogeneous equilibrium applies to all cases where, at a constant temperature, one and the same chemical substance is present in two or more physical conditions, or "phases," in contact and in equilibrium with each other. We have, for instance, the common case of a liquid, say water, in contact with its vapor, or the liquid in contact with its solid phase (ice) and its vapor; or, we may have a gas, say oxygen, in contact with its solution in some solvent like water. We may have a solid, like cane sugar, in contact with its solution. ”

“ You know enough chemistry to realize that everything—water, air, food, all things which we use in every-day life—are merely combinations of certain simple elements. As you have seen me, by means of an electric current, decompose a jar of pure water into its two component parts,—two molecules of hydrogen to every molecule of oxygen,—so you can bring these same elements together in the gaseous state ”

“ Glycerine is a good tempering substance, and to this may be added a small amount of sulphate of potash.
Fluxing.—The word flux means to fuse or to melt, or to put into a liquid state. The office of a flux is to facilitate the fusion of metals. But fluxes do two things. They not only aid the conversion of the metal into a fluid state, but also serve as a means for facilitating the unity of several metals which make up the alloy, and aid in uniting the parts of metals to be joined in the welding of parts
p. ”

“ Theoretical Explanation.—We proceed to examine how far the same formulae as hold for gases apply to the available energy of matter in solution which is so dilute that each molecule of the dissolved substance, though possibly the centre of a complex of molecules of the solvent, is for nearly all the time beyond the sphere of direct influence of the other molecules of the dissolved substance. The available energy is a function only of the co-ordinates of the matter in bulk and the temperature ”

“ By an effort of the will, then, I combine and condense these gases--which consist principally of oxygen, hydrogen, nitrogen, and carbon--into flesh, blood, water, or anything else. You have already learned on earth that, by the application of heat, every solid and every liquid substance, which is solid or liquid simply because of the temperature at which you find it, can be expanded into gas or gases; and that by cold and pressure every gas can be reduced to a liquid or a solid. On earth the state of a substance, whether solid, liquid, or gaseous, depends simply upon those two conditions. ”

“ The third of the fundamental laws of chemistry stated above (generally known as the law of Gay-Lussac) declares that, when two or more of the factors or products of a chemical process are aëriform, the volumes of these gaseous substances bear to each other a very simple ratio. Here, again, numerous experiments may be contrived to illustrate the law. Water, when decomposed by electricity, yields hydrogen and oxygen gases whose volumes bear to each other the ratio of two to one. ”

“ For the comprehension of that general plan according to which a change of state of substances (combined or dissolved, solid, liquid, or gaseous) takes place, it is very important to make a distinction at this boundary line (on approaching zero of decomposition, volatility, or solubility) between an insignificant amount and zero, but the present methods of research and the data at our disposal at the present time only just touch such questions (by studying the electrical conductivity of dilute solutions and the development of micro-organisms in them) . ”

“ Now, the number of ions is given by the concentration of the solution, for even if all the ions are not actively engaged in carrying the current at the same instant, they must, on any dynamical idea of chemical equilibrium, be all active in turn. The charge on each, as we have seen, can be expressed in absolute units, and therefore the velocity with which they move past each other can be calculated. ”

“ We think fit to call different kinds of matter carbon, oxygen, hydrogen, and nitrogen, and to speak of the various powers and activities of these substances as the properties of the matter of which they are composed.
When hydrogen and oxygen are mixed in a certain proportion, and an electric spark is passed through them, they disappear, and a quantity of water, equal in weight to the sum of their weights, appears in their place. There is not the slightest parity between the passive and active powers of the water and those of the oxygen and hydrogen which have given rise to it. ”

“ If the so-called chemical elements are simply so many stable molecular aggregates, whose differences are due to different modes and degrees of aggregation, then the gases of our earth are simply the most diffused state in which masses of these aggregates can be obtained. A gas is a diffused mass of homogeneous molecules, and this definition is as true of the compound gases, steam, carbonic acid, or vapor of alcohol, as it is of the simple ones, such as hydrogen, nitrogen, or vapor of mercury. ”

“ In such a case the molecules of the solutum will be divided between the liquid and the gas in a (sensibly) constant ratio (the volume of the liquid and gas being kept constant) , simply because every molecule, moving as if there were no others, would spend the same part of its time in the vapor and in the liquid as if the others were absent, and the number of the molecules being large, this would make the division sensibly constant. ”

“ The dehydrating agents rapidly lose their efficiency on exposure to the air.
CRUCIBLES It is often necessary in quantitative analysis to employ fluxes to bring into solution substances which are not dissolved by acids. The fluxes in most common use are sodium carbonate and sodium or potassium acid sulphate. In gravimetric analysis it is usually necessary to ignite the separated substance after filtration and washing, in order to remove moisture, or to convert it through physical or chemical changes into some definite and stable form for weighing. ”

“ If, therefore, that fluxion be denoted by ̇υ, we shall have flux. Q ́ q + R ́ r &c. = ̇υ, and consequently Q ́ q + R ́ r &c. = υ. But Q ́ q + R ́ r &c. (by the same notation) appears to be the fluxion of Q ́q ́ + R ́r ́ &c. (or of Qq + Rr &c.) arising by substituting u for ẏ, making u alone variable, and casting off ̇u. Whence the following
General Rule. Take the fluxion of the given expression (whose fluent is required to be a maximum or minimum) making ẏ alone variable ”

“ An increase in the size of the system is not, however, the only way by which the velocity might fall below that calculated for the hydrogen molecule, for we must remember that the hydrogen molecule, whose coefficient of diffusion is 1.7, is not charged, while the ion is. ”

“ Now the potential in any of the liquids or solids for the substance which it yields in the form of gas has very nearly the same value when the liquid or solid is in equilibrium with the gas-mixture as when it is in equilibrium with its own gas alone. ”

“ Oxygen, hydrogen, carbon, and nitrogen, uncombined, present, for example, one state of material forces, which manifests one set of phenomena; water, formed by the combination of oxygen and hydrogen, is another state, less simple, and manifesting less simple phenomena; alcohol, resulting from the union of oxygen, hydrogen, and carbon, is another state, more complex, and manifesting more complex phenomena; carbonate of ammonia, consisting of oxygen, hydrogen, carbon, and nitrogen, is another state, more complex still, and manifesting phenomena of corresponding complexity ”

“ Of the four chief elements which, in various combinations, make up living bodies, three are gaseous under all ordinary conditions and the fourth is a solid. Oxygen, hydrogen, and nitrogen are gases which for many years defied all attempts to liquefy them, and carbon is a solid except perhaps at the extremely high temperature of the electric arc. Only by intense pressures joined with extreme refrigerations have the three gases been reduced to the liquid form. ”

“ The actual amount of dynamical energy set free by the union of this pound of charcoal with atmospheric oxygen is equivalent to the mechanical raising of eleven and a quarter million pounds one foot high. Let us further consider the dynamical forces inherent in the molecules of free gases, and look to a molecular explanation of the three states of matter, the solid, fluid, and gaseous. In solids the atoms are held together with a rigidity that develops the full strength of cohesive force. ”

“ As most gases are invisible, I shall exhibit gaseous diffusion to you by means of two gases, ammonia and hydrochloric acid, which, when they meet, form a solid product. The ammonia, being the lighter gas, is placed above the hydrochloric acid, with a stratum of air between, but you will soon see that the gases can diffuse through this stratum of air, and produce a cloud of white smoke when they meet. ”

“ From this it is evident that the analogy of substances forming a solution plays an important part, and as aqueous and all other solutions are liquids, there is good reason to believe that in the process of solution solid and gaseous substances change in a physical sense, passing into a liquid state. These considerations elucidate many points of solution—as, for instance, the variation of the co-efficient of solubility with the temperature and the evolution or absorption of heat in the formation of solutions. ”

“ Such a diffusion, of one mile in depth of chlorine, would be equal to lifting up to the hydrogen a shell of solid iron two feet thick. Whether we explain the distinguishing principle of the constitution of gases as a mutual repulsion of their molecules, or, according to a late theory, as an incessant motion and clashing of atoms, there is nothing in either to warrant the supposition of the lifting or overcoming any considerable weight in the diffusion of gases. ”

“ They have a tendency to penetrate each other, as it were; for instance, if you take a jar of heavy gas, such as carbonic gas, set it with its mouth upwards, then invert over it another jar containing hydrogen, a gas nearly twenty-two times lighter, in a very short time the two gases will have become thoroughly mixed, the heavy carbonic acid having risen, and the light hydrogen fallen, until the gases are thoroughly mixed, each jar containing an equal quantity of each gas. ”

“ The probability is that the hydrocarbons and carbo-hydrates which, in traversing the system, are transformed by communicated chemical action, evolve, during their transformation, not heat alone but also other kinds of force. ”

“ The importance of the fact that the velocity and therefore the energy of the corpuscles emitted from the metal is independent of the intensity of the incident light can hardly be overestimated. It raises the most fundamental questions as to the nature of light and the constitution of the molecules. What is the source of the energy possessed by these corpuscles? Is it the light, or in the stores of internal energy possessed by the molecule? Let us follow the consequences of supposing that the energy comes from the light. ”

“ The gases themselves are differentiated into what we call oxygen, nitrogen, carbonic acid, and aqueous vapor, each of which exerts its special influence in the economy of vital existence, and without any one form of which, so far as we can see, life would be impossible. Another portion of the matter composing the earth exists in the liquid state, the chief form of which is water, of which more than half the weight of all organized beings consists. ”

“ Solubility.—Some pairs of liquids are soluble in each other in all proportions, but, in general, when dealing with solutions of solids or gases in liquids, a definite limit is reached to the amount which will go into solution when the liquid is in contact with excess of the solid or gas. This limit depends on the nature of the two components, on the temperature and on the pressure. When the limit is reached the solution is said to be saturated, and the system is in equilibrium. ”

“ How is it to get into the plant?
When one liquid, say spirit, is poured into another, say water, the two gradually mix. If we suppose these liquids to consist of a number of molecules, then, mixture may be taken to be the result of the displacement say of one molecule of water by one molecule of spirit, and so, throughout the whole quantity of liquid, there is displacement and replacement till at length equilibrium is restored and a thorough diffusion results. This power of diffusion does not always exist. The molecules of water and of oil will not mix or diffuse freely through each other. ”