In ascertaining the quantities of the different com pounds in mineral waters, the steps to be followed must, of course, vary in every different case, according to the substances contained in the water. A few ex amples will suffice to illustrate the methods employed.
In fixing the quantities of the different compounds, we may state them either in their crystallized condi tion, in which case they generally contain water ; but it is better, if possible, to reduce them to dryness. This is done by exposing them to a red heat for some time, by which the whole of the water is driven off. Some of the salts which we procure undergo decomposition when subjected to a strong heat ; such is the case with the carbonates and some others. We cannot, therefore, in this way, ascertain their quantity in the dry, or, as it is called, real state. NVe may do this, however, by de composing them, ascertaining the quantity of the pro duct, and finding how much of the decomposed salts is necessary to form these products.
78. Nitrate of Potassa. To ascertain the quantity of nitrate of potassa, suppose it exists in water, along with sulphates, and muriatcs of the alkalies, decom pose these by the acetates of baryta and silver. After filtration, evaporate to dryness, and digest the residue in alcohol, which will dissolve the acetates formed, and will leave the nitrate.
79. Nitrate of lime. Suppose this contained in the water along with muriates of soda and lime, evaporate to dryness, and digest the residue in alcohol, which will dissolve the earthy salts, and leave the muriate of soda. Evaporate the alcoholic solution to dryness, and weigh the residue, after being dried ; then dissolve it in water, and ascertain the quantity of muriatic acid, by precipi tation with nitrate of silver, (43.); this will give the quantity of the muriate of lime, which, subtracted from the weight of the residue, leaves that of the nitrate of lime.
80 Carbonates. By boiling the fluid after it has been deprived of its sulphuretted hydrogen, (56.) the carbonates are precipitated, probably mixed with sul phate of lime. The carbonates may be that of lime, magnesia, alumina, or iron ; the precipitate must there fore be digested in diluted muriatic acid, which will dis solve them all, except the alumina and the sulphate of lime. if any thing be left undissolved, it must be ex
posed to a red heat, and weighed ; it is then to be boiled in the solution of subcarbonate of soda, and muriatic acid added, to saturate the alkali. By boiling the fluid, carbonate of lime, and alumina, if present, will be pre cipitated. Digest the precipitate in acetic acid, by which the alumina will be left ; this, after being dried, will give the weight of the earth, and its weight, sub tracted from that of the residue, the quantity of the sul phate of lime.
81. Carbonate of iron. The muriatic solution may contain lime, magnesia, and iron. By the addition of ammonia, the iron and part of the magnesia will be pre cipitated. By digesting the precipitate in acetic acid, the magnesia will be dissolved, and the iron will be left. It must be dissolved in muriatic acid, and precipitated by the addition of sub-carbonate of soda. The precipitate, after boiling the fluid, must be washed, dried, and weighed, which gives the weight of the carbonate of iron.
82. Carbonate of Lime. The acetic solution of the magnesia must be mixed with the rnuriatic solution ; to this, sulphuric acid must be added, and the fluid evapo rated, and the sulphate of lime will be deposited. Alter being dried, it must be weighed, and its equivalent of carhcnate of lime ascertained.
83. Carbonate of Magnesia. By the addition of sub carbo.arte of soda to the solution, the carbonate of mag nesia will he precipitated. It must be dried and weigh ed The solution, however, still contains sulphate of lime, and carbonate of magnesia. Jt must therefore be evaporated to dryness, and the residue washed with wa ter, which will dissolve the sulphate, and leave the car bonate. The weight of the latter of these must he added to that of the carbonate formerly procured. The solu tion of the sulphate must be evaporated to dryness, and the residue ignited, and the equivalent of carbonate of lime added to that already mentioned.