Page:Text-book of Electrochemistry.djvu/37

 ��OLDER ELECTROCHEMICAL VIEWS.

��CHAP.

��After oxygen followed sulphur, chlorine, bromine, iodine, etc., which are all separated from their compounds at the positive pole. With oxygen, these negative substances form strong acids, which likewise separate at the positive pole. Close to the negative substances Berzelius set in the series those elements (all positive bodies) which could form acids with oxygen, and the stronger the acid which was formed, the nearer did these elements stand to the negative substances. Further, he placed those bodies which give difficultly reducible compounds with oxygen at the positive end of the series, on the assumption that compounds are the more stable the greater the charge possessed by the positive component.

Metals capable of separating others from their compounds were regarded as more positive, and substances with similar chemical properties were placed together. If an element lay between two others as far as chemical properties were con- cerned, it was placed between them also in the series — for example, bromine between chlorine and iodine.

In this way Berzelius, after many alterations, set up the following so-called elect rochemicai series, beginning with the negative elements : —

��Oxygen

�Boron

�Palladium

�Thorium

�Sulphur

�Carbon

�Silver

�Zirconium

�Selenium

�Antimony

�Copper

�Aluminium

�Nitrogen

�Tellurium

�Uranium

�Yttrium

�Fluorine

�Tantalum

�Bismuth

�Beryllium

�Chlorine

�Titanium

�Tin

�Magnesium

�Bromine

�Silicon

�Lead

�Calcium

�Iodine

�Hydrogen

�Cadmium

�Strontium

�Phosphorus

�Gold

�Cobalt

�Barium

�Arsenic

�Osmium

�Nickel

�Lithium

�Chromium

�Iridium

�Iron

�Sodium

�Vanadium

�Platinum

�Zinc

�Potassium

�Molybdenum

�Mercury

�Manganese

� �Tungsten

�Khodiiim

�Cerium

� ��From what has been said, it is evident that this series was really only a chemical scheme, and that it is incomplete and arbitrary, may be gathered from the number of alterations

�� �