A treatise on chemistry. Vol. 1, The non-metallic elements / by Sir H.E. Roscoe & C. Schorlemmer ...

  • Henry Enfield Roscoe
Date:
1881
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Licence: Public Domain Mark

Credit: A treatise on chemistry. Vol. 1, The non-metallic elements / by Sir H.E. Roscoe & C. Schorlemmer ... Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

    51/792 page 35
    THE ATOMIC THEORY. 36 Daltou was a man to whom original work was a necessity.^ In the preface to the second part of his New System of Chemical Fldl- osophy, published in 1810, he clearly shows his independence and even disregard of the labours of others, for he says— Having been in my progress so often misled by taking for granted the results of othei'S, I have determined to write as little as possible but what I can attest by my own exjjerience. As early as 1802, in an experimental inquiry into the pro]3or- tions in which the several gases constituting the atmosphere occur, Dalton clearly points out that the elements of oxygen may combine with a certain portion of nitrous gas (our nitric oxide) or with twice that portion, but with no intermediate quantity, and this observation was clearly the first which led to the possibility of drawing np the table already given.^ In that table, it will be seen that the relative weights of the smallest particle of nitrous gas is given as 9 3, that of Azot (nitrogen) being 4*2, and that of oxygen 5'5. Da-lton clearly intending by this to express that the gas is a compound of one atom of nitro- gen with one atom of oxygen, whilst the substance to which he gives the name of hypo-nitric acid (now called nitrogen peroxide), is a compound in which one atom of nitrogen is combined with two of oxygen, and therefore having the rela- tive atomic weight of 152.^ The first public announcement of the atomic theory, and of the law of combination in multiple proportions upon which it was founded, was, singularly enough, not made by Dalton himself, but by his friend. Professor Thomas Thomson, of Glasgow, who pul)- lished in 1807 an accoiuit of Dalton's discovery in the third edition of his System of CJmnistry. In the following year (1808) Dal- ton made known his own views in the remarkable book entitled A Neiv System of Chemical Philosophy, m which (Part i. \). 213) he says— It is one great object of tliis woi'k to ,show the importance and advantage of ascertaining the relati\e weights of the ultimate particles, both of simple and compound bodies, the number of simple elementary particles which constitute one compound particle, and tiic number of less compound particles 1 TiOn.sdale's Zt/c q/ Ballon. 'Longmans, 1874. Manchester Memoirs, 2nil Series, vol. i. pi. 250. ^ Certain inaccuracies in the values of the weights of some of the coniponnd.= occur in this table; thu.s, 4-2 + 5-S = 97, whilst 9-3 ajipcars ojijw.site nitrons oxide. Whether these are merely printei-'s errois or are to be c.xiiliiined in some other way can now only bo conjectured. See l?o.scoc on Diilton's First Table of .'\toniic Weights. Manchester Lit. and J'hil Son Mcvi. 3rd Seric.s, vol. v. ii. 1^09 ia74-5. 3—2
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