The alloy with 12% of silicon is white, hard and brittle.
The eutectic alloy itself, fig.
Sometimes the whole alloy is a uniform solid solution.
The term "alloy" does not necessarily imply obedience to the laws of definite and multiple proportion or even uniformity throughout the material; but some alloys are homogeneous and some are chemical compounds.
From the alloy containing 25% of silicon, the excess of magnesium is removed by a mixture of ethyl iodide and ether and a residue consisting of slate-blue octahedral crystals of magnesium silicide is left.