Chemical compound

“ He thus arrived at his dualistic theory of chemical compounds, which attained great prominence and prevailed for a long time in chemical theory. According to this idea, each compound was supposed to be made up of a positive and a 304negative atom or group of atoms. For example, the formulas for potassium nitrate, calcium carbonate, and sulphuric acid corresponded to K2O.N2O5, CaO.CO2 and H2O.SO3 where we now write KNO3, CaCO3 and H2SO4, and the theory was extended to embrace organic compounds also. ”

“ Care should be exercised to distinguish chemical compounds from simple mixtures. Air is not a compound, but a mixture of oxygen, hydrogen and nitrogen gases. Water, however, is a compound of oxygen and hydrogen. Both salt and [30] sugar are compounds, but if we grind them together, we do not have a new compound, but a mixture of two compounds. Most of the common things around us are mixtures of different compounds or substances. Rocks are mixtures of many different compounds. Wood is, likewise, formed of many different substances. ”

“ This explains why salts are usually inactive and neutral in character, while acids and bases are active agents. Thus we see why the most positive or the most negative elements in general have the strongest affinities, while those intermediate in the list are inactive, and have weak affinities; why alloys of the metals are weak compounds; why a neutral substance, like water, has such a weak affinity for the salts which it holds in solution; and why an aqueous solution is regarded as a mechanical mixture rather than a chemical compound. ”

“ Chemical affinity is a well recognized force. Under the action of this force chemical compounds are produced and different compounds formed under different conditions. The properties of the different compounds differ with their composition, and the more complex are the compounds the more varied their properties. Now it might be assumed as an hypothesis that there could be a chemical compound so complex as to possess, among other properties, that of causing the oxidation of food to occur in such a way as to produce assimilation and growth. ”

“ In organic as in inorganic chemistry, atoms are bound together by chemical affinity, though it was formerly supposed that an additional or vital force was instrumental in forming organic compounds. For this reason none of these substances, it was thought, could be built up in the laboratory, although many had been analyzed. In 1828 the first organic compound, urea, was artificially prepared, and since then thousands have been synthesized. They are not necessarily manufactured from organic products, but can be made from mineral matter. ”

“ Compare CO and CO2. (3) In the arrangement of atoms, i.e. the molecular structure. Ethyl alcohol and methyl ether have the same number of the same elements, C2H6O, but their molecular structure is not the same, and hence their properties differ.
Qualitative analysis shows what elements enter into a compound; quantitative analysis shows the proportion of these elements; structural analysis exhibits molecular structure, and is the branch to which organic chemists are now giving particular attention. `
A specialist often works for years to synthesize a series of compounds in the laboratory. ”

“ The molecule of an element usually contains two atoms; that of a compound may have two, or it may have hundreds. For a given compound the number is always definite.
Chemism is the force that binds atoms together to form molecules. The sugar molecule contains atoms, forty-five in all, of three different elements: carbon, hydrogen, and oxygen. That of salt has two atoms: one of sodium, one of chlorine. Should we say "an atom of sugar"? Why? Of what is a mass of sugar made up? A molecule? A mass of carbon? A molecule? Did the chemical affinity of the acid break up masses or molecules? ”

“ 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. ”

“ The higher the molecular tower, or the more atoms it contains, the greater its liability to fall. Some organic compounds contain hundreds of atoms, and hence are easily broken down, or, as we say, are unstable. Inorganic compounds are, as a rule, much more stable than organic ones. It is not always true, however, that the compound with the least number of atoms is the most stable. SO2 is more stable than SO3, but H2SO3 is less so than H2SO4. Chapter XXXIV.
VAPOR DENSITY AND MOLECULAR WEIGHT. Examine a liter measure, in the form of a cube,—cubic decimeter, —and a cubic centimeter. ”

“ It will still help to make iron rust; and salt will be salty, whether or not it is dissolved in water. That is why [pg 310] solutions are only mixtures and are not chemical compounds.
Everything in the world is made of atoms. Everything in the world is either an element or a compound or a mixture. Most plant and animal matter is made of very complicated compounds, or mixtures of compounds. ”

“ Test for a Carbonate.—To test for a carbonate, treat the substance with an acid; CO2 is formed; pour the gas into a solution of lime-water, and a white insoluble precipitate is formed, CaCO3.
[883]
TABLE OF ALL THE KNOWN CHEMICAL ELEMENTS The Chemical Elements are the simplest known constituents of all compound substances. Chemists regard them as elements or elementary substances only when they have been proved to be not compound. The elements are somewhat arbitrarily divided into metals and non-metals, the former constituting by far the larger class. ”

“ The view long maintained—until late in the nineteenth century, in fact—that organic and inorganic chemistry are separated from each other by a wide gap, is no longer held. Hundreds of organic substances, some of them of great complexity, have been made in the chemist’s laboratory, and can now be classed as properly with inorganic as with organic substances. The gap has been closed, and there is now but one chemistry. Only the most intricate chemical compounds still lie beyond the chemist’s grasp, and the isolation of these may be at any time overthrown. ”

“ So the synthesis of a single organic compound sufficed at a blow to break down the chemical barrier which the imagination of the fathers of the science had erected between animate and inanimate nature. Thenceforth the philosophical chemist would regard the plant and animal organisms as chemical laboratories in which conditions are peculiarly favorable for building up complex compounds of a few familiar elements, under the operation of universal chemical laws. ”

“ The fundamental distinction supposed to be at the basis of all chemical study, that between elements and compounds, is found to be inapplicable when we study such bodies as cyanogen, a compound of the two elements carbon and nitrogen, that behaves like an element. ”

“ The chemical combination of two substances produces, as is well known, a third substance, with properties different from those of either of the two substances separately, or of both of them taken together. Not a trace of the properties of hydrogen or of oxygen is observable in those of their compound, water. The taste of sugar of lead is not the sum of the tastes of its component elements, acetic acid and lead or its oxide ”

“ 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. ”

“ A compound is a substance which is made up of elements united in exact proportions by a force called chemism, or chemical affinity.
A mixture is composed of two or more elements or compounds blended together, but not held by any chemical attraction.
To which of these three classes does sugar belong? Carbon? The solution of sugar in water?
Carbon is an element; we call its smallest particle an atom.
An atom is the smallest particle of an element that can enter into combination. Atoms are indivisible and usually do not exist alone. Both elements and compounds have molecules. ”

“ ACID-AMIDES, chemical compounds which may be considered as derived from ammonia by replacement of its hydrogen with acidyl residues, the substances produced being known as primary, secondary or tertiary amides, according to the number of hydrogen atoms replaced. ”

“ The attempt is historically interesting as being the first systematic endeavour to gain an insight into the constitution of chemical compounds—that is, to determine the manner in which the constituent atoms are grouped or arranged with respect to one another, or, in other words, to distinguish between the empirical and the rational composition of substances, which is the ultimate aim of modern chemistry. ”

“ Its affinity for H2O is so great that it takes the latter from the air, if exposed.
Experiment 65.—Saturate some unslaked lime with water, in an e.d., and look for the results stated above, leaving it as long as may be necessary.
105. Resume.—From the experiments in the last few chapters on the three divisions of chemical compounds, acids, bases and salts, we have seen (1) that acids and bases are the chemical opposites of each other; (2) that salts are formed by the union of acids and bases; (3) that some acids can be obtained from their salts by the action of a stronger acid ”

“ Their complexity is indicated by the fact that the molecule of sugar contains 45, and that of stearine no less than 173, constituent atoms. The chemical compounds of carbon are far more numerous than those of all the other chemical elements combined ”

“ Besides the characteristic substances of these three classes, protoplasm contains certain other chemical compounds, like the various salts of sodium, chlorine, magnesium and potassium, and a few others, which bring the list of chemical elements to the number twelve. We have already noted how strikingly small and restricted is the list of elements composing living matter as compared with the long array of eighty-odd different kinds of chemical atoms existing in the world as a whole. ”

“ The synthesis of other so-called organic compounds followed, and at present it is known that the same chemical laws apply to all substances whether formed in the living organism or prepared in the laboratory from inorganic constituents. ”

“ The first class includes such substances as iodine, mercury, iron, carbon, and their various compounds, and such bodies as alcohol, chloroform and chloral, all of which are found in nature or can be prepared by ordinary chemical processes of manufacture. From plants many substances are obtained which at the present time we are unable to make in the chemical laboratory, and of the constitution or composition of which we are in many cases ignorant. ”

“ The fundamental task of inorganic chemistry is still connected with the classification of elements and compounds. The investigation of the classification of carbon compounds forms the field of organic chemistry; while general or physical chemistry deals with the laws of reaction, and the influence of various forms of energy in furthering or hindering chemical change. ”

“ Of which is the sugar experiment an example? Metathesis is an exchange of atoms in two different compounds; it gives rise to still other compounds.
A chemical change may add something to a substance, or subtract something from it, or it may both subtract and add, making a new substance with entirely different properties. Sulphur and carbon are two stable solids. The chemical union of the two forms a volatile liquid. A substance may be at one time a solid, at another a liquid, at another a gas, and yet not undergo any chemical change, because in each case the chemical composition is identical. ”

“ Organic compounds, on which our life and living depend, consist chiefly of four elements: carbon, hydrogen, oxygen and nitrogen. These compounds are sometimes hard to analyze, but when once the chemist has ascertained their constitution he can usually make them out of their elements—if he wants to. He will not want to do it as a business unless it pays and it will not pay unless the manufacturing process is cheaper than the natural process. ”

“ For, even the preachers have begun to tell us that God is radium, or ether or some scientific compound, and that the worst we wicked ones may expect is a chemical reaction. ”

“ In the lectures and recitations a systematic study of the aliphatic and aromatic compounds is undertaken. In the laboratory certain selected experiments in the analysis and synthesis of organic compounds is carried out as well as exercises in the study of the chemical properties of various classes of compounds. The course is conducted with special reference to the industrial applications of organic chemistry. Some of the newer physico-chemical tools used in the study of the science will be considered. ”

“ Instead of acids uniting with bases to give rise to a third kind of bodies, salts, we have carburets, bases, uniting by twos or by threes, with or without the loss of one of their elements, and forming double or triple molecules of compounds, which may still be of the same chemical type. ”