Compound bodies

The difficulty in gaining useful compositional knowledge at this early stage was neatly expressed by Paul Walden. In the early days every new compound body represented a new riddle. The only method of analysis available was that by fire, and the products were necessarily assumed to be simpler than the body that had been heated and perhaps to be the actual components of that body. This has been the most naive assumption as we saw presented and argued by Beguin. 

A] change of properties, and a production of new properties, may be considered as criterions, by which compound bodies, chemically combined, may be distinguished from bodies formed merely by mixture or apposition of integrant parts in which latter kind of bodies, the properties are intermediate betwixt the properties of several component parts, and no new properties are produced. 

The key to this system lies in the recognition that components by which compound bodies are named must be simple bodies or considered as simple rather than elements in the ultimate meaning of that term. This was not the first time Guyton had made the distinction between the philosophical and operational components. Only a few years earlier in his Elemens de chemie, he had carefully identified the ultimate, metaphysical components, the earth, water, air, and fire, as the natural elements, and the more operational ones as chemical elements.The latter, though presumably composed of the natural elements, were still simple according to art for it has not yet been possible to separate their principles. Nor was Guyton the first to make this kind of distinction. In the late seventeenth century Nicholas Lemery had written... 

Daltons synthesis of the weights of the compound bodies from the weights of their atoms makes the pattern of multiple proportions quite... 

When these four elements combine to form the many substances that make up the material universe, their properties then blend into a composite in which the elements lose their identity. Aristotle makes it clear that he considers compound bodies homogeneous even in their smallest conceivable parts, so that the ultimate particle of flesh is still flesh. This is also the idea of Anaxagoras, already cited. To these simple substances of like particles Aristotle gives the name homoiomere. It logically follows that the con cept of the four elements of Aristotle differs fundamentally from that of Empedocles, for the smallest particle of a given substance would, by the theory of Empedocles, be... 

A firm believer in the atomic theory of Dalton, Berzelius made his new symbols stand for the relative atomic weights of the atoms. The initial letter capitalized represented one atom of the element. The symbols stood for definite quantitative measurements and enabled us to indicate without long periphrases the relative number of atoms of the different constituents present in each compound body. Thus they gave a clue to the chemical composition of substances. This was a tremendous step toward making chemistry a mathematical science. 

But I must confess I am jealous of the term atom for though it is very easy to talk of atoms, it is very difficult to form a clear idea of their nature, especially when compound bodies are under consideration. 

Memoir on Azot, and on the Question, Whether it be a simple or a compound Body (p. 353)... 

The element is a simple body which actually enters into the mixture [mixtion] of compound bodies [corps composes] and to which they can be finally... 

Stahl elaborated a more complex, hierarchical composition of bodies. All natural bodies were either simple or compound. Simple bodies were principles. Compound bodies had three levels of composition mix d, compound, and aggregate. Principles composed mixts directly. Mixts, in turn, composed compounds and aggregates. In other words, one had to make a distinction between the original mixts ( mixts consisting of principles ) and the secondary mixts ( bodies compounded of mixts ). Ideally, principles had to be simple substances that existed in the mixts before chemical analysis and to which mixts were resolved after the analysis, as had long been prescribed in the French didactic tradition ... 

Chemistry is almost the only Art, that seems suited to cultivate this second, and most valuable method of making physical Observations. Tis this that resolves compound Bodies into their simple parts, and know, what new appearances, and powers, will thence arise Tis this, that separates, or compounds various Bodies, and then examines them nicely with a determinate, and well observed degree of Heat, in order to find out if possible, what it is in them that nature is chiefly engaged about And lastly, Tis Chemistry that by these means discovering how it may exactly imitate the natural and common Phaenomena abovementioned, hence truly explains, and exhibits to us the instruments by which nature so efficaciously operates and thus pries into her most secret methods of working, and very often prudently directs and improves them to its own advantage. ... 

The nature, the number, the arrangement, and the distance of the atoms are the same. If this is the case what becomes of the definition of chemical species, so rigorous, so remarkable for the time at which it appeared, given by Chevreul in 1823 In compound bodies a species is a collection of individuals identical in the nature, the proportion, and the arrangement of their elements. 

If we examine even the most simple combinations of carbon, its oxides, niturets, hydrurets, and chlorides,—among all other compound bodies, we shall not find any at all resembling them. 

From these examples, we can begin to understand the aim of Boerhaave s chemistry and the function of the chemical instruments within it. For Boerhaave, chemical operations could not be deployed reliably to make claims regarding the composition of compound bodies. Because of this problem Boerhaave saw the need, as he stated in the Elementa, to fix some sure limits to our Art, which we must not exceed if we would avoid mistakes, and come at the truth. 37 First among these limits was determining in... 

Considering several kinds of solvents (also called menstruums), Boerhaave began to write about affinities. We easily perceive, he explained, that many [solvents] unite bodies together, as well as separate them into their minutest parts. It was, he noted, a common observation that when the particles of some solvents had dissolved their solvends, they then united themselves to the particles of the body dissolved and formed a new compound body, oftentimes... 

An acid is a compound of an electro-negaiim elemeni or residue with ky drogen xdhich hydrogen it can part wUh in exchange for an electro-positive Yemeni urithoui formation of a base. An acid may also be defined aa a compound body which evolves toater by its action upon pure caustic potash or soda. 

When simple compound bodies which are either wholly or in part capable of assuming the aeriform state are subjected to heat, they or their most volatile constituents, upon reaching the required temperature, rise in the form of vapor. If these vapors, in their transit, are intercepted by a surface of a lower temperature, they condense and take a solid or liquid form, according to their nature. If the product is a solid, it is termed sublimate, and the process by which it is obtained is auhiimation. If it is liquid or gas. it takes the name of distillate, and the operation which yields it that of distillation. 

The forms of matter with which we are most familiar, however, are not elementary. If we examine the matter of w hich a rock, a tree, an animal, the atmosphere, or the ocean are respectively composed, we shall find that all those objects may be proved to contain two or more distinct kinds of matter that is, two or more elements. Where this is the case, we c the substance a compound body. 

But when we call any substance elementary, or simple, we do not mean that it is certainly or essentially so we only say that hitherto, in our hands, and exposed to all the various agencies which we can bring to bear on it, it has yielded only one kind of matter, or element, and no more. In the early part of the present century, the alkalies and earths were believed to be elementary bodies, because only one kind of matter had ever been obtained from them but the new power of galvanism enabled Davy to discover that all these bodies were compound. It is far from being improbable that, in the progress of discovery, several, perhaps many, of the 55 elements which we are now compelled to admit, may, in like manner, prove to be really compound bodies,... 

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