A dictionary of chemistry, on the basis of Mr. Nicholson's: in which the principles of the science are investigated anew, and its applications to the phenomena of nature, medicine, mineralogy, agriculture, and manufactures, detailed (Volume 2).

  • Andrew Ure
Date:
1821
Catalogue details

Licence: Public Domain Mark

Credit: A dictionary of chemistry, on the basis of Mr. Nicholson's: in which the principles of the science are investigated anew, and its applications to the phenomena of nature, medicine, mineralogy, agriculture, and manufactures, detailed (Volume 2). 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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    a«id tha» in the straw-coloured; and the lat- ter acid retains it wiih less force than the red nitrous acid; and niirous gas holds it with still more force than the red nitrous acid. This accounts for the separation of oxygen gas from the colourless nitrous acid (nitric acid) when exposed to the sun, at the same time that the acid becomes coloured. Nitrous acid in any other state will afford no oxygen, when exposed to the sun. Why the gaseous oxide should be more soluble in water than the nitrous gas, is what 1 cannot account for, unless it be occasioned by the smaller size of its calorific atmos- pheres, which may admit its atoms to come within the gravitating influence of that fluid. It is impossible to deny the praise of sin- gular ingenuity, and justness, to the above passages; and every one must be struck with their analogy, both as to atomical doctrnus, and the calorific atmospheres of gases, single and compound, with the language and views expanded at full length in Mr Dalton's new system of Chemical Philosophy, first framed about the year 1803, and published in 1808. It appears that this philosopher, after medita- ting on the definite proportions, in which oxy- gen was shown by M. Proust to exist in the two oxides of the same metal, on the suc- cessive combinations of oxygen and azote, and the proportions of various other chemi- cal compounds, was finally led to conclude, that the uniformity which obtains in corpus- cular combinations, results from the circum- stance, that they consist of one atom of the one constituent, united generally with one atom of the other, or with two or three a- toms. Ana he further inferred, t^at the re- lative weights of these ultimate atoms might be ascertained from the proportion of the two constituents in a neutral compound. Chemistry is unquestionably under great ebligations to Mr. Dalton, for the pains with which he collated the various analyses of chemical bodies, by different investigators; and for establishing, in opposition to the doctrine of indefinite affinity, taught by the illustrious Bt-rthollet, that the different com- pounds of the same principles did not pass into each other by imperceptible gradations, but proceeded, per saltttm. in successive pro- portions, each a multiple of the first. By correcting and extending Kichter's scale of reciprocal saturation, and reviving Mr. Hig- giiis's long neglected discovery of multiple proportion, Mr Dalton has been no mean contributor to the advancement of the sci- ence. It is difficult to say how far his figur- ed groups of spherical atoms have been be- neficial or not. They may have had some ]use in aiding the conception of learners, and perhaps in giving a novel and imposing air I to the atomical fabric. But their arrange- { nient, aiid even their existence, are alto ■5 01 gcther hypothetical, and therefore ought to have no place in physical demonstrations. That water is a compound of an atom oxvgen and an atom of hydrogen, is assum- ed by Mr. Dalton as the basis of his system. But two volumes of hydrogen here combine with one of oxygen. He therefore infers, that an atom of hydrogen occupies double the bulk, in its gaseous state, of an atom of oxvgen. These assumptions are obviously gratuitous. I agree with Dr. Prout in think- ing that Sir H. Davy has taken a more phi- losophical view of this subject. Guided by the strict logic of chemistry, he places no hvpodiesis at the foundation of his fabric. Experiment shows, 1st, That in equal vo- lumes, oxygen Weigh 16 times more than hy- drogen; and 2dly, That water is formed by the union of one volume of the former, and two volumes of the latter gas, or by weight of 8 to 1. We are not in the least authori- zed to infer from this that an atom of oxy- gen weighs 8 times as much as an atom of hydrogen. For aught we know, water may! be a compound of 2 atoms of hydrogen, and 1 of oxygen; in which case we should have the proportion of the weights of the atoms, as given by equal volumes, namely, I to 16. There is no good reason for fixing on one compound of hydrogen, more than on an- other, in the determination of the basis of the equivalent scale. If we deliberate on that combination of hydrogen in which its agency is apparently most energetic, name- ly, that with chlorine, we would surely never think of pi'chi ng on two volumes as its unity or least proportion of combination; tor it is one volume of hydrogen which unites with one volume of chlorine, producing two vo- lumes of muriatic gas. Here, therefore, we see that one volume of hydrogen is quite ade- quate to effect, in an active gaseous body of equal bulk, and 36 times i's weight, an en- tire change of properties. Should we as- sume in gaseous chemistry, 2 volumes of hydrogen, as the combining unit, or as re- presenting an atom; then it should never unite in 3 volumes, or an atom and a half with another gas. Ammonite, however, is a compound of 3 volumes of'hydrogen with 1 of azoic; and if 2 volumes of hydrogen to 1 of oxygen be called an atom to an atom, sure- ly 3 volumes of hydrogen to 1 of azote should be called an atom and a half to an atom. Yet the Daltonian Commentator, on the second occasion, counts one volume an atom of hydrogen, and on the first, two vo- lumes an atom. We would steer clear of all these gratui- tous assumptions and contradictions, by ma- king a single volume of hydrogen represent its atom, or prime equivalent. There is an advantage, says Dr. Prout, in considering the volume of hydrogen equal to the atom, as, in this case, tUe specific gravities of most,
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