This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
Light, white, friable masses, or a light, white powder, odorless and tasteless, insoluble in alcohol, and almost insoluble in water, to which, however, it imparts a feebly alkaline reaction. When strongly heated, it loses water and carbonic acid gas, and is converted into magnesia. It ia soluble in diluted hydrochloric acid, with copious effervescence. Magnesium carbonate for the purpose of manufacturing artificial mineral waters is, as a rule, produced by mutual decomposition of a soluble magnesia salt with an alkali carbonate within the mixture in fountain, whereby carbonate of magnesium precipitate is produced, which is soluble in carbonated water, particularly under pressure. But where this process, on account of its by-products, is not possible, the magnesium carbonate hydrate must be applied where magnesium carbonate is required.