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.
Asbestos is an article which the bottling and carbonating industry has more or less use for, especially in the construction of filters. It is a fibrous variety of hornblende and serpentine, produced by the decomposition of these minerals. Its composition varies somewhat according to its origin. The mass of the material consists essentially of magnesium silicate, but in most cases also contains lime, and in many -cases oxides of iron and alumina.
Good asbestos has the following properties: It resists the action of the most powerful flame (white heat); it is fire-proof. Acids (dilute) and alkalies produce no effect, even under a high pressure, but it is decomposed by hot concentrated sulphuric acid. It is a poor conductor of heat. It has lubricating properties. Asbestos is generally divided into three classes: 1. Asbestos without fibrous structure; this is generally used for making asbestos powder. 2. Asbestos with fibrous structure, characterized by a yellowish cinnamon brown color, and containing many foreign bodies; this is very fragile. 3. Fibrous asbestos, adapted for the manufacture of woven goods.
Besides many practical employments of asbestos, which is also applicable to the machinery of bottling establishments, its use as a filtering medium is becoming recognized. Several water filters in which asbestos is an important part are known in the trade, and have given good results in the way of mechanical filtration.
In Germany the asbestos is very finely divided by a patented process. The asbestos is first coarsely ground, and then mixed with some granular crystalline carbonate which must be soluble in acids. The carbonate should possess a hardness between 3 and 4.5 according to the mineralogi-cal scale. The mixture is intimately ground together in a mill. Afterwards the mass is treated with an acid until the carbonate has been dissolved out. The escaping carbonic acid gas causes the asbestos fibres to be loosened and disintegrated from each other so as to render the mass porous. Of course, it must be thoroughly washed with water before being used.