Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 3, 1802).djvu/236

214] rest for two, three, or more hours, or even as many days. At the end of this period, the investigation must be repeated; the fluid compared with water newly drawn from the spring; and, if any separation of parts take place, any scum arise, or sediment be formed at the bottom of the glass, they ought to be carefully collected for future examination.

IV. These glasses should next be deposited in a warm place; till, the watery parts being totally exhaled, a dry substance only reniains; which ought to be compared with the sediment obtained from the same water by evaporation over the fire, in order that the real difference between both dry substances, may be more precisely ascertained.

V. It will next be requisite to analyze the water chemically: for this purpose, a certain porfion of it ought to be taken from the spring, and poured into a retort with a wide neck, to which a clean glass receiver, well luted, should be affixed. The whole must now be placed over a moderate fire, so as to simmer the water till all the aqueous particles are come over; when the vessels should be suffered to cool, the distilled water carefully drawn off, and deposited in a well-closed glass: then the dry substance must be separated from the bottom of the retort, weighed, and likewise preserved in a glass.

VI. The distilled water must next be examined by various tests, to ascertain whether it materially differ from distilled common water; or whether it be impregnated with any saline or mineral particles, similar to those observed in the natural fluid, when first drawn from the well. In this process, if the water contain any common salt, it will, with a solution of silver, assume a white colour: if vitriol of iron be one of its ingredients, it will become black, on being mixed with pulverized galls.

VII. In case the water be suspected to contain any salts, it will be advisable gently to boil a quantity of the dry substance obtained by distillation, in five or six times its weight of pure common distilled water, such as is totally divested of all mineral particles. By this process, the saline matter will be dissolved or suspended in such water, in the form of a solution, which, on being filtred, and evaporated to dryness, will re-produce its salt. And, if there should be other salts in the same solution, they may all be obtained, by repeating the filtration and evaporation.

VIII. After the different salts are thus evolved, it will perhaps be attended with some difficulty to ascertain those species which are denominated neutral. This may be effected by observing the appearances assumed by such salts, on being mixed with other matters. Thus, marine or sea-salt may be known by the white vapour which it emits when in contact with oil of vitriol, and also by its taste, as well as by its cubical figure, on being crystallized. Another distinguishing characteristic of neutral salts is, their property of producing or regenerating sulphur, when mixed and liquefied with salt of tartar, and pulverized charcoal. If, therefore, two parts of such salt be mixed with one part of salt of tartar, and a similar portion of carbon in powder, and the whole be melted in a crucible, a reddish mass will be formed, possessing an alkaline sulphureous taste, and which will