New conversations on chemistry : adapted to the present state of that science, wherein its elements are clearly and familiarly explained : with one hundred and eighteen engravings illustrative of the subject, appropriate questions, a list of experiments, and a glossary : on the foundations of Mrs. Marcet's "Conversations on chemistry" / by Thomas P. Jones.

  • Jones, Thomas P., 1774-1848.
Date:
1833
Catalogue details

Licence: Public Domain Mark

Credit: New conversations on chemistry : adapted to the present state of that science, wherein its elements are clearly and familiarly explained : with one hundred and eighteen engravings illustrative of the subject, appropriate questions, a list of experiments, and a glossary : on the foundations of Mrs. Marcet's "Conversations on chemistry" / by Thomas P. Jones. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    mical(20). You will find, therefore, Caroline, that chemistry is no narrow or confined science, but that it comprehends every thing material within our sphere of observation. Caroline. It must indeed be inexhaustible, and I am now at a loss to conceive how any proficiency can be made in a science whose objects are so numerous. •Mrs B. If every individual substance were formed of different materials, the study of chemistry would, indeed, be endless; but you must observe that the various bodies in nature are composed of certain simple substances, or elementary principles, which are not very numerous(21). Caroline. Yes; I know that all bodies are composed of fire, air, earth and water; I learnt that many years ago(22). Mrs B. But you must now endeavour to forget it. I have already in-» formed you how great a change chemistry has undergone since it has become a regular science. Within these forty years especially, it has ex- perienced an entire revolution, and it is now proved that neither fire, air, earth, or waiter, can be called elementary bodies. An elementary body is one that has never been decomposed, that is to say, separated into other substanccs(23). Air, earth, and water, are all of them susceptible of decom- position, and the same may probably be asserted of fire(2i). Emily. I thought that decomposing a body was dividing it into its mi- nutest parts. And if so, I do not understand why an elementary substance is not capable of being decomposed, as well as any other. J\Trs B. You have misconceived the idea of decomposition; it is very different from mere division. The latter simply reduces a body into parts, but the former separates it into the various ingredients, or materials, of which it is composed(25). If we were to take a loaf of bread, and separate the several ingredients of which it is made, the flour, the yeast, the salt, and the water, it would be very different from cutting or crumbling the loaf into pieces(26). Emily. I understand you now very well. To decompose a body is to separate from each other the various simple or elementary substances of which it consists. Caroline. But flour, water, and the other materials of bread, according to your definition, are not elementary substances. Mrs B. No, my dear; this separation of the ingredients of bread would be only a partial decomposition; but it may serve to give you a familiar idea of what is intended. The elementary substances of which a body is composed are called the constituent parts of that body; in decomposing it, therefore, we separate its constituent parls(27). If, on the contrary, we divide a body by chopping it to pieces, or even by grinding or reducing it to the finest powder, each of these small particles will still consist of a portion of the several constituent parts of the whole body: these are called the integrant parts(28); do you un- derstand the difference? 20. How would you discover whether a body had been acted upon me- chanically or chemically? 21. Are all substances which differ formed of different materials* 22. Of what elements does Caroline suppose all bodies to be formed? 23. What is meant by an elementary substance? 24. What is said respecting what were once called the four elements? 25. What is the difference between mere division and decomposition!1 26. Give the example. 27. What is meant by the constituent parts of a body? 28. What by integrant parts}