Notes for students in chemistry : being a syllabus of chemistry compiled mainly from the manuals of Fownes-Watts, Miller, Wurz, and Schorlemmer / by Albert James Bernays.

  • Bernays, Albert James, 1823-1892.
Date:
1878
Catalogue details

Licence: Public Domain Mark

Credit: Notes for students in chemistry : being a syllabus of chemistry compiled mainly from the manuals of Fownes-Watts, Miller, Wurz, and Schorlemmer / by Albert James Bernays. Source: Wellcome Collection.

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    only one-Lalf it-< atomic weight; but.when potassium do( s so the equivaleiits are in tlie same jiroportioTi as their atomic weigHts Chemical reactions may bo rejiresentcd symbolically m the form of equations, the symbols of the reagents being placed to tlie left and those of the results on the same line to the right, only separated by =. Thus: + OH, = OK., + H^. Jn thi.s case, the molecule of kalitjm (potassium) decomposes the molecule of water, into Ihe molecule of totassoxide, and tlie molecule of i-nDROCEN. Multivalent elements often exhibit varying degrees of equivalency. Thus Carbon is quadrivalent in Cn! and bivalent in CO. Nitrcgen is univalent m JsoO, triv.leit in N^O^ and quinquivalent in N,0,. The variation mostly takes place by two units of equivalency. The atomic weights of those elements which are known to exist as o-as or vapor, are, as a rule, proportional to their spe- cific gravities. Taking the specific gravity of hydrogen as i, then are the sp. grs. of Oxygen, Nitrogen, Chlorine and Fluorine^ and of the vapors of Bromine, Iodine, Sulphur, &clemiim and Tellurium (compared under the same conditions of teraperatoe and pressure), identical with their atomic weights. Exceptions to this rule are exhibited by arsenieum and phosphorus, who^e vapor-den.sities are twice their atomic weights, and by Cad- mium and Mei-curv, who.se vnpoi-deusities equal only halt tlieir respective atomic'weights. With these exceptions, the com- bining volumes of all elementary gases are equal. The mole- cules of compound bodies in the gaseous state occupy the space of two volumes of hydrogen. As the molecule ol an elenientaiT oas is made up of two atoms, it may be said that equal volumes of all gases contain equal numbers of molecules, or that the molecules of all gases occupy equal volumes (Law ot Avogadro). Thus is afforded a sure mode of fixing the molecular constitu- tion of all compounds obtainable as gasrs, and of ascertaining the atomic weights of the elements. When it is said that the sp. gr. of any compound gas or vapor, referred to hydrogen as unity, is equal to half its atomic or molecular weight, it must be remembered that a lew excep- tions are Icuown, Thus ammonthm chlokide C1H,N, occupies, as vapor, four times the space of an atom of hydrogen. The same exceplions we have in the cases of phosphoric chloride CI; OIL OF VITRIOL SO,(OH).,; MEROrRCIIS CHLORIDE Hg.CU : AMMO- NIUM HYDROGEN .SULPHIDE SH(H,N) &c. &c . ^1^^^, ^ - tan extent, the explanation may he m the supposition, that the high temperature to whiph they are subjected bungs about a partial decomposition or dissociation. , , i If olie or more of llie atoms of a fully saturated molecule he removed, it is obvious that the resi.h.e will be no longer satu- rated • such residues arc called Kadicles. In the case ot the