Of other metals first detected by the spectroscope mention is to be made of indium, determiped by F.
Rubidium, caesium, thallium, indium and gallium were first discovered by means of this instrument; the study of the rare earths is greatly facilitated, and the composition of the heavenly bodies alone determinable by it.
To take an example: 38 parts of indium combine with 35.4 parts of chlorine; hence, if the formula of the chloride be InCI, InC1 2 or InC1 3, indium has the atomic weights 38, 76 or 114.
The specific heat of indium is o 057; and the atomic heats corresponding to the atomic weights 38, 76 and 114 are 3.2, 4.3, 6.5.
The elements gallium and indium were discovered in blende.
INDIUM (symbol In, atomic weight 114.8), a metallic chemical element, included in the sub-group of the periodic classification of the elements containing aluminium, gallium and thallium.
, P 444) It occurs naturally in very small quantities in zinc blende, and is best obtained from metallic zinc (which contains a small quantity of indium) by treating it with such an amount of hydrochloric acid that a little of the zinc remains undissolved; when on standing for some time the indium is precipitated on the undissolved zinc. The crude product is freed from basic zinc salts, dissolved in nitric acid and the nitric acid removed by evaporation with sulphuric acid, after which it is precipitated by addition of ammonia.
The precipitated indium hydroxide is converted into a basic sulphite by boiling with excess of sodium bisulphite, and then into the normal sulphite by dissolving in hot sulphurous acid.
Indium is a soft malleable metal, melting at 155° C. Its specific gravity is 7.421 and its specific heat 0.05695 (R.
Indium oxide, In203, is a yellow powder which is formed on ignition of the hydroxide.
The hydroxide, In(OH) 3j is prepared, as a gelatinous precipitate, by adding ammonia to any soluble indium salt.
Three chlorides of indium are known: the trichloride, InC13j a deliquescent salt, formed by heating a mixture of the oxide and carbon in a current of chlorine; the dichloride, InCl2, obtained by heating the metal in hydrochloric acid gas; and the monochloride, InCl, which is prepared by distilling the vapour of the dichloride over metallic indium.
Indium Sulphate, Ine(SO 4) 3, is obtained as a white powder very soluble in water by evaporating the trioxide with sulphuric acid.
An indium ammonium alum, In2(S04)3 (NH4)2S04.24H20 is known.
The atomic weight of indium has been determined by C. Winkler and by R.
Indium salts can be recognized by the dark blue colour they give in the flame of the Bunsen burner; and by the white beads of metal and the yellow incrustation formed when heated on charcoal with sodium carbonate.
We must refer to Kayser and Runge's Handbuch for further details, as well as for information on other spectra such as those of silver, thallium, indium and manganese, in which series lines have been found.