Element Argon Ar, Noble Gas. obtained from chemical compounds, in having a somewhat greater density.

Element Chlorine, Cl, Hallogen.

Element Iodine, I, Halogene. Is allied to chlorine and bromine, and forms a third similar element. Of the three, it has the highest combining weight, amounting to 126. 86, and its properties show deviations from those of bromine chiefly in the same direction as those of bromine deviate from chlorine. Vapour is very considerable, being about nine times as great as that of air. The molar weight is 254 and the vapour has, therefore, the formula I.

Element Krypton, Kr, Noble Gas. From Greek κρυπτον, krypton. Abundance in air is about 1. Of air contains 1 sm.

Element Selenium, Se, Non Metal. Whereas the amorphous selenium does not conduct the electric current to a measurable extent, the property of conductivity is possessed by the crystalline form. Hydrogen selenide is the hydrogen acid of selenium in the same sense as hydrogen sulphide is the hydrogen acid of sulphur; its aqueous solution contains the ions Se. By heating selenium with iron filings, and to treat this with hydrochloric acid. In a manner perfectly analogous to the prep.

Element Tellurium, Te, Metalloid. While iodine is very similar to bromine, if not in external appearance, at least in the nature of the corresponding compounds, the differences between selenium and tellurium are more pronounced, so that it has repeatedly been regarded as doubtful whether these two elements ought to be regarded as members of the same family. The combining weight of tellurium, Te. Combines with the metals to form tellurides; these correspond to the sulphides.

From a Greek word meaning strange one or stranger; it was a stranger indeed in krypton fraction. Abundance in atmosphere is 0. By volume; deposits are estimated as 1.