Chemical Properties of Germanium

Germanium resembles tin in behaving both as a bivalent and a quadrivalent element. Both oxides, GeO and GeO₂, are slightly soluble in water, forming faintly acid solutions; they also dissolve in acids, but form no oxy-salts. The sulphides are well known, and they resemble those of tin in forming thio-salts with alkali sulphides. Germanium resembles silicon in forming the hydride GeH₄ and the chloroform GeHCl₂, whilst the complex fluoride K₂GeF₆ resembles potassium silicifluoride, K₂SiF₆. The existence of germanium tetra-ethyl, Ge(C₂H₅)₄, is in accord with the position the element occupies at the head of Subgroup IV B in the Periodic Table.

Germanium compounds do not colour the Bunsen flame, but the spark spectrum of the element shows a number of bright lines, especially in the blue and violet.

From germanous solutions alkalis precipitate the yellow hydroxide, potassium ferrocyanide the white ferrocyanide, hydrogen sulphide the brown sulphide GeS; germanous solutions reduce chromate and permanganate and precipitate gold from the chloride.

Alkalis yield no precipitate with germanic solutions, since hydrated germanic oxide becomes colloidal and excess of alkali forms germanate. Ammonia and ammonium and sodium carbonates partially precipitate the hydrated dioxide. The most characteristic reaction is the formation of the white sulphide, soluble in excess of ammonium sulphide; this compound serves for the gravimetric estimation of germanium.