Philosophical transactions, Vol. L. Part I. For the year 1757. / Giving some account of the present undertakings, studies, and labours, of the ingenious, in many considerable parts of the world.

by Various; Royal Society

It appears from the 11th experiment, that an addition of common water causes the mineral water to precipitate its ochre; and the reason of this is obvious: for if these ochrous parts be altogether terrene, as they appear to be, and exist in the water unconnected with any other principle, then it must happen, that as these parts are uniformly diffused thro' the water, in which they are suspended as in a menstruum; by the addition of common water, this menstruum being diluted, the cohesion of these terrene parts must be thereby weakened, and their contact destroyed; so that their menstrual equilibrium being thus taken off, they can be no longer supported in the fluid, but must be precipitated by the force of their own gravity.

Exp. 12. When the water was exposed for some days to the air, there was a cremor separated from it of a shining chalybeat colour. This, like other kinds of cremor, takes a considerable time to compleat its intire separation from the fluid, out of which it is expelled: for when it was despumated, a new cremor always succeeded, until the whole quantity, which the water contained, was exhausted.

13. When this cremor first appeared on the water, it was of a faint blueish colour; but as it increased, it changed into a deeper and more bright shining blue: and, after longer standing, it became blotched with various colours, as red, orange, yellow, green, blue, purple, and violet.

14. A quantity of the water being put in a gentle heat, this cremor was quickly separated from it, and appeared on the surface of the water. A like quantity of the water, with its cremor already upon its surface, was put over a gentle heat, which by degrees broke the cremor into very small parts; but whether they did evaporate, or precipitate in the water, I could not be certain. But, by other trials, this cremor was found to have a great degree of fixity, bearing a considerable heat without avolation; yet not without the appearance of some of its parts flying off, altho' most of them were fixed; because what remained lost its fine colours, and was changed into a shining chalybeat colour.

15. The water of the lower spring afforded a much less quantity of the cremor, than the water of the upper spring. It took also a longer time to separate, was of a blueish colour, and had not the vivid colours, which the water of the upper spring shewed.

16. When ol. tart. p.d. and spirit of sal ammoniac were added to the water, it did not separate its cremor.

This cremor, which is separated from the water, is the same with that, which appears on the surface of a solution of vitriolum Martis, when exposed for some time to the air; and an infusion of iron in common water also emits a cremor of the same kind. I remember, as I was once carefully observing a large glass full of chalybeat water, which contained much of this cremor; soon after it was exposed to the air, I observed a tenuious blueish vapour rising in the parts of the water next the surface, which very much diminished its transparency; and by degrees this vapour was emitted by the lowest parts of the water: but as the cremor increased on its surface, the water became gradually deprived of the blueish tincture, which it received from this halituous body; which was apparently nothing else but the parts of the cremor separating from the water, and ascending upwards. From whence we may conclude, that this cremor consists of the very finest part of iron attenuated to the highest degree.

It has been the opinion of most naturalists, that these kind of mineral waters do abound in sulphureous parts. This they have conjectured from the foetor, that often attends them. But in what quantity or form these parts exist in the fluid, or by what means they can be rendered conspicuous, has not as yet been sufficiently determined. Yet, I think, we may suspect some of the parts of this cremor to be sulphureous. They are volatile, and, being heated, do fly off from the pure metalline parts, which being more fixed, are thereby left destitute of those vivid colours, which they enjoyed from the sulphureous parts. These are evident marks of sulphur, and are altogether analogous to some other appearances of that mineral. Another observation tending to support this is the want of those vivid colours in the cremor, which appears on an infusion of iron; the reason of which seems to be the loss of the sulphureous parts of the chalybeat minerals by avolation, during the operations of the fire, which they undergo in refining.

It appears from the fifteenth experiment, that the water of these two springs contains a very different proportion of this cremor: and from the last, that it is precipitated along with the ochrous parts, which happens upon the affusion of these alkaline liquors.

The next trials were in quest of alum.