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.
Should these operations be carried on in the cylinder or condenser of a continuous apparatus, English plan, it is necessary to work it intermittently and to disconnect the pump from the fly-wheel, while agitating the charged cylinder. However, this course is followed but very seldom, and impossible to pursue where the continuous apparatus has a small cylinder or globular condenser attached The general practice is to use slate tanks, Fig. 246; they should be covered with glass plates or fine muslin to keep dust and dirt out. The desired quantity of water is poured in, the necessary salt solutions are added and mixed, time being allowed to settle, then the tank is connected with the pump by means of a tin pipe or flexible rubber hose, and the liquid continuously drawn through a lawn sieve in the solution pan, pumped through the machine to be impregnated with the carbonic acid gas, and then immediately bottled. This process is very defective, as will be readily seen.
The readily soluble components only enter into the beverage, while those chemical combinations which are produced within the mixture itself upon combining of the different solutions, and form precipitates, or those components which have to be added in their hydrated state, and are but soluble under prolonged pressure of carbonic acid gas, remain undissolved at the bottom of the tank, or, if they are left out, there is no imitation of the natural water. Also, the atmospheric air cannot be properly excluded when the continuous process is followed; therefore no proper water in which iron or manganese enters can be made, and reduced iron or carbonate of manganese could not enter at all. The most important operation in preparing such mineral waters is the removal of atmospheric air from the apparatus and water. As all the oxidulated iron and man-ganesium salts easily absorb oxygen, they would quickly get oxidized by the air absorbed by the water, and soon cause turbidity of the beverages.
It is decidedly wrong to leave out the troublesome or difficultly-soluble minerals, as is done so frequently to ease the manufacture, except in cases specified later on. An alteration in the composition changes the charader and nearly always the physiological action and medicinal value of a mineral water. We therefore prefer the intermittent system or the connection of special fountains with continuous apparatus, where mineral waters are to be made, to allow the proper method of working.