These require the aid of the powerful machine employed by soda-water manufacturers, to charge the waters strongly with carbonic acid gas. The gas is made from whiting and diluted sulphuric acid, and is forced by a pump into the watery solution. Sometimes the gas is produced by the mutual action of the ingredients introduced into the bottle of water, which must be instantly closed; but this method is found practically inconvenient, and is only adopted in the absence of proper apparatus. The quantity of gas introduced is directed, in the French and American pharmacopoeias, in most cases, to be 5 times the volume of liquid. For chalybeate and sulphuretted waters, the water should be previously deprived of the air it naturally contains, by boiling, and allowing it to cool in a closed vessel.

There are various manufacturers of aerated-water machines, and of syphon bottles for holding these waters when made. The names and addresses of these makers may be found in any trade directory.

Simple Aerated Water. Carbonic acid gas mater. Water charged with five or more volumes of carbonic acid gas, as above.

Alkaline Aerated Waters. Aerated soda and potash waters should be made by dissolving a drachm of the carbonated alkali in each pint of water, and charging it strongly with carbonic acid gas. But the soda water of the shops generally contains but little (or no) soda.

Aerated Magnesia Water. This is made of various strengths

Murray's and Dinneford's Fluid Magnesia may be thus made: - To a bailing solution of 16 oz. of sulphate of magnesia in 6 pints of water, add a solution of 19 oz. of crystallized carbonate of soda in the same quantity of water; boil the mixture till gas ceases to escape, stirring constantly; then set it aside to settle; pour off the liquid, and wash the precipitate on a cotton or linen cloth, with warm water, till the latter passes tasteless. Mix the precipitate, without drying it, with a gallon of water, and force carbonic acid gas into the mixture under strong pressure, till a complete solution is effected. The Eau Magnesienne of the French codex is about a third of this strength; and we have met with some prepared in this country not much stronger. See Liquor MagnesiAe Carbonatis, B. P.

Carbonated Lime Water. Carrara Water. Lime water (prepared from lime made by calcining Carrara marble) is supersaturated by strong pressure, with carbonic acid; so that the carbonate of lime at first thrown down is re-dissolved. It contains 8 grains of carbonate of lime in 10 fluid oz. of water.

Aerated Lithia Water. This may be conveniently made from the fresh precipitated carbonate, dissolved in carbonated water, as directed for fluid magnesia. Its antacid and antilithic properties promise to be useful. See Liquor LithiAe Effervescens, B. P.