Philosophical transactions, Vol. L. Part I. For the year 1757. · Various
II.
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. _Exp._ 17. A quantity of the water being kept for some time in a boiling heat, and after it was cool being filtred quite clear from its ochrous matter, it still retained a subacid and aluminous taste in a very strong degree. 18. To an ounce of common spring-water there was added two gutts of fresh sweet milk. This mixture being shaken, the milk mixed intimately with the water, without any kind of coagulation. 19. The same experiment being made with the mineral water, the milk, upon its affusion, was so curdled, or separated into clouds, that the greatest shaking could not mix or incorporate it with the water. 20. This experiment being also made with a weak solution of alum in spring-water, its effects upon the milk were not in the least different from those of the mineral water. 21. And the same trial being again repeated with the water, when boiled and filtred from its ochrous parts, the milk was in the same manner coagulated as before elixation. 22. One part of sweet milk being added to four parts of the mineral water, the milk subsided, and formed a cloud in the bottom of the glass, leaving the upper parts of the water clear. This mixture being heartily shaken, the milk mixed so well with the water, that it appeared to be but a very little curdled.
23. When a larger quantity of milk was added to a smaller quantity of water, and even when equal parts of the milk and mineral water were mixed and shaken together, there could be no curdling or coagulation observed. 24. An equal quantity of the water and milk being boiled together, the greatest part of the milk was coagulated into a thick white curd; and the remainder, with the mineral water, turned of a pure white milky colour, which drank like whey, and was very agreeable. 25. Eight gutts of sweet milk being added to four ounces of the water, and the mixture boiled, part of the milk was thereby curdled, and swam upon the top of the water. The ochrous parts of the water were likewise separated, and falling to the bottom, their colour did not appear of a clear yellow, as usual, but was something milky. All these experiments strongly indicate the existence of alum in this water. It retains its aluminous taste, and coagulates milk, after the chalybeat parts are almost all expelled by elixation. The coagulation of the milk demonstrates an acidity in the water, and the other appearances shew that acidity to be owing to an aluminous salt. It appears, that the milk requires a large quantity of the water, to make a sensible coagulation in it: for, in the 22d experiment, one part of the milk being added to four parts of the mineral water, the coagulation was scarcely discernible: and in the 23d, when an equal or larger quantity of milk was added to the water, the coagulation was not at all observable. I have heard it confidently averred, that this mineral water did not at all curdle milk; which, I suppose, has been thro’ a mistake in the experiment, in adding too large a proportion of milk to the water: for in this way the coagulation cannot be observed.
I imagined, that when the water was boiled with milk, the mixture would have become of a muddy yellow colour, by the separation of the ochre: but it did not even appear, that the ochre was at all separated from the mixture, as it is from the water when boiled by itself. On the contrary, not only the coagulum, but also the liquor, was of a pure white colour, and of a pleasant taste: and this makes me think it worth the inquiring into, whether or not the water does retain its medical qualities after it is prepared in this manner with milk? For, if it does, such a preparation might certainly be very serviceable in many cases. These experiments, which we next relate, do not only ascertain the existence of alum in the water with greater certainty, but also, that there is a particular kind of earth conjoined with this salt.
_Exp._ 26. An English quart of the water being kept boiling for a quarter of an hour, it turned thick, muddy, and yellow, by the separation of its ochrous parts; and, being set to cool in a clean bowl, the next day all the ochre was subsided to the bottom, from which the water was carefully filtred: whereby it became almost as clear and limpid as before the elixation, retaining a sharp aluminous taste, but was deprived of the strong ferrugineous taste, which it had at first. This water was again boiled; by which means it was again turned a little yellow, by the separation of some more ochre. It was therefore again filtred, and rendered clear, and its aluminous taste was stronger than before. After this filtration, the water was evaporated in a sand-heat to about a sixteenth part of the original quantity, and then it tasted like a strong solution of alum joined with a small degree of a chalybeat taste. And this being totally evaporated in a glass, there adhered upon its sides a pure white salt; and a larger quantity of the same salt remained in the bottom of the glass, which was not so white, but more impure than the former, and of a brown colour. 27. This salt, thus procured from the water, being mixed with distilled vinegar and spirit of vitriol, there was not the least effervescence produced.
28. Some of the brown-coloured salt being put upon a red-hot iron, it did neither sparkle nor decrepitate; but was turned into a blackish cineritious substance, which in a short time became a white calx. And tho’ some of the salt was put upon the iron finely powdered, yet it concreted, and run together in a cinder, whose cohesion was afterwards destroyed when calcined by a further degree of heat. 29. As I was accidentally deprived of the opportunity of obtaining crystals of this salt, which would have been the best means of knowing to what species it was to be referred; I dissolved the whole mass in a small quantity of spring-water, and, by filtrating this solution, I obtained a large proportion of fine earth of a brown colour. 30. This solution of the salt afforded a deep blue tincture with galls. 31. The same solution, being mixed with syrup of violets, became of a reddish colour. 32. Saccharum Saturni being added to the solution, precipitated a thick lactescent cloud. 33. Ol. tart. p.d. being also added to this solution, it caused no visible effervescence, yet raised some bubbles of air, and caused a coagulation of many small brown terrene nubeculæ in the water; which, after standing some time, subsided to the bottom, and left the water clear. These experiments do plainly evince, that this water contains an aluminous salt, conjoined with a fine terrene substance, which is probably a part of the matrix, from whence the salt has been formed.
This salt gives no signs of any alkaline principle; but, on the contrary, of an acidity, as its solution reddens with syrup of violets. With this salt there are also intimately conjoined some very subtile chalybeat parts, which are not separable from it by elixation or evaporation. Alum is distinguishable from all other mineral salts, by liquifying and bubbling upon a red-hot iron, and turning into a white calx. But this could not be well expected from this aluminous salt, which we had extracted from the water, because it was extremely foul, by being combined with so large a proportion of earth; which earthy parts were the occasion of turning the salt of a blackish colour upon the iron. However, we see it turns white by a further degree of heat. But if the salt had been dissolved, filtrated, and crystallized, till it had been purified and freed from this terrene matter, it would then certainly have had the same appearance upon the red-hot iron, as a pure aluminous salt. Again, as it is peculiar to an aluminous salt to liquify in some degree with fire, so we see, that this was evidently the case of this salt. Its eliquation indeed could not be so remarkable, as in pure alum, because of its being mixed with so much earth; but that it did liquify in some degree is plain, because the whole mass of salt and earth, even when reduced to a powder, ran all together like a cinder.
The experiment upon the solution of this salt with ol. tart. p.d. is also a further proof of what we have already asserted: for tho’ there was no visible effervescence, yet the bubbles of air shew, that there was an intestine conflict of the oil with the acid principle in the solution; which being absorbed by the alkali, the earth was precipitated, to which it formerly adhered. The two next experiments were made in order to discover, whether an acid or alkaline principle prevailed in the water. _Exp._ 34. Forty gutts of the syrup of violets being added to an ounce of the water, the mixture became of a bright sea-green colour. 35. A quantity of water being kept boiling for five minutes, and afterwards allowed to stand till it became clear, was carefully filtrated from its ochrous sediment: after which, upon its mixture with syrup of violets, it turned of a faint reddish colour. From these experiments we infer, that this mineral water contains both an alkaline and an acid principle; the former consisting of the ochrous and ferrugineous parts, which are separated from the water by elixation; and the latter of the aluminous salt, which remains in the water after elixation. The following trials were made in order to know what effects are produced in the water by being exposed to the air; and in what respects the waters of the two springs differed from each other.
_Exp._ 37. An English quart of the water of each of the springs being fully exposed to the air in two China bowls, the next day that of the under spring was neither altered in its taste, colour, or transparency, nor in any other shape whatever; but that of the upper spring appeared of a yellowish colour, altho’ it was clear and transparent as the other. On the second day the taste of the waters scarcely appeared to be any way diminished. No sensible change could be observed in the lower water; but the upper water was become more yellow than it was the day before, yet without any loss of its transparency. They both tinged of a deep blue colour with galls; which tinctures appeared equally deep and strong, as they did before the waters were exposed to the air. The third day the lower water appeared clear and colourless as before, only its surface was covered with a few small spots of cremor. The upper water appeared more yellowish than formerly, and its surface was almost wholly covered over with the cremor. They both afforded a tincture with galls, which was not sensibly different from what they gave before their exposure. On the fourteenth day the water of the under well had precipitated a yellow ochrous sediment, but the other water a more considerable quantity. A large quantity of cremor continued also to swim upon the surface of the upper water, but there was very little separated from the water of the under well. Both waters being now tried with galls, instead of the deep blue colour, which they did formerly exhibit, they now became only of a deep purple colour.
On the twentieth day the visible appearance of both waters was the same as when last observed. On the thirty-eighth day they both afforded as deep a purple colour with galls, as they did three weeks before; and during that time also they had not precipitated any more of their ochrous parts, nor suffered any other sensible alteration. The water of the upper well being filtrated from all the ferrugineous matter, which it had separated during these thirty-eight days, was rendered almost as limpid and clear as when newly taken from the well: but, being boiled for some time, it became of a turbid yellow colour; and being allowed to stand, it again precipitated abundance of an ochrous sediment; and being filtrated, and mixed with galls, it received a faint purple colour of a blueish hue. 38. A bottle of the water of each of these springs, being carefully sealed, carried to Moffat, and kept for two months, suffered not the least alteration during that time, but was as fresh as when immediately taken from the fountain. And I am informed, that after it is carried to Edinburgh, and to places at a greater distance, it will keep a much longer time without being any way spoiled.
I believe it will appear from these observations, that this mineral water continues longer intire, and particularly that it retains the quality of tinging with galls longer, than most others of the chalybeat kind: at least, of a great number, which I have seen described, I do not remember one, that retains it near so long, when exposed to the open air. Many of them lose this quality intirely in a few hours; and it is greatly impaired in the same time, even in those which retain it longest. But this water, we see, remains exposed to the open air for days, without almost any alteration. This may perhaps be owing either to the larger proportion of ferrugineous parts, with which it is impregnated; to their being attenuated to a greater degree; or to their more perfect commixture with the water, by means of the aluminous salt. The longer time, that any mineral water does remain intire, without any separation of its mineral parts; or the longer it retains the same form, which it has when newly taken from the spring; the more perfect is the commixture of these parts with their fluid vehicle: and I believe, upon that account, will be more effectual for medicinal uses: for which reason, I suppose, these waters may prove a more beneficial medicine, than any others of the ferrugineous kind, whose mineral contents are not so intimately commixed with the aqueous fluid.
As these waters are so long in separating their mineral contents, they appear particularly well adapted for being transported to distant places: for by this quality they are fitted to undergo a long carriage, and to be kept a considerable time, without any diminution of their medicinal virtues. It must also be noticed, that the water of the under well is by much the best of the two for carriage, or for being long kept, as it is longer in separating its mineral contents than the upper one. From these experiments it is evident, that there is a considerable difference betwixt the waters of the two springs. The upper one contains a much larger quantity of ochrous earth, and metalline cremor, than the under one; which is the reason, why it yields a deeper colour with galls, as may be observed in the first experiment. I suspected, on the other hand, that the under water contained a greater proportion of alum, than the water of the upper spring; but this I cannot affirm, as I find I had neglected to make the experiment, which would have determined whether it be so or not. Tho’ the mineral contents of these two waters be similar, yet, if they be thus mixed in them in different proportions, this must certainly create a difference between them, which deserves to be attended to, as it may be sufficient to disallow of their being used promiscuously, since their medicinal effects may be thereby different.
But now, to sum up the evidence, which these experiments, taken all together, do afford, concerning the mineral ingredients of this Spaw; I think they determine, with some degree of certainty, that it contains two different principles of iron, both of which are fixed. The one, which is the ochrous earth, is a true _minera ferri_, and, altho’ it be a crude mineral, exists in the water in a very fine and subtile form; the other, which is the cremor or pellicle, whose parts are also extremely attenuated in the water, appears to be iron, not in its mineral, but in its metalline form, and, when thrown up upon the surface of the water, shews itself like an extreme thin _lamina_ of that metal. There seems also to be some small proportion of sulphur joined with the metalline cremor. The other mineral ingredient, which enters into the composition of this Spaw, is a considerable proportion of an aluminous salt, which is conjoined with a small quantity of a light brown-coloured earth (probably a part of the matrix whence the salt is formed), and still more intimately connected with some of the chalybeat parts of the water, which are not separable from it either by elixation or evaporation. Whether these be saline or terrestrial, I cannot determine. Having thus endeavoured to discover, by some plain and simple experiments, the mineral principles, with which this medicinal water is impregnated; I shall now only add some observations, with respect to the origin of steel waters, and particularly of this Spaw, whose origin, I think, is thereby discovered and ascertained in a very obvious manner.
Among several things, that are still deficient in the history of mineral waters; an exact knowlege of their origin seems to be the chief; that is, from what fossils, and in what manner, these waters do acquire the mineral substances, with which they are impregnated. As this happens in the bowels of the earth, and is therefore far removed from our view, it is not surprising, that there has been so little discovered concerning it; tho’ indeed there have been many elaborate hypotheses framed in order to account for it. The writers on mineral waters have been of very different and opposite opinions concerning their origin. They have disagreed widely amongst themselves; and I very much suspect, that the accounts, which most of them give of this matter, are not agreeable to truth: particularly with respect to chalybeat waters, I have seen none, who have given a satisfactory account of their origin. They have all agreed, that iron, or the vitriol of that metal, does exist in mineral waters; but they have never yet agreed, how they came to exist in them, or in what manner mineral waters come to be imbued with these fossils.
Some of the more ancient writers cannot comprehend, how simple water should be intimately impregnated with so many different kinds of minerals, except by the means of some powerful agent. And as they thought nothing more proper for communicating and mixing mineral substances with water, than violent heat, they therefore termed all mineral waters, of whatever kind, by the name of _thermæ_. They saw some spring from the earth extremely hot, others moderately hot, others tepid, others excessively cold: they concluded from this, that all such various degrees of heat in these waters were owing either to the different degree of subterranean fire, which they had undergone; or else to the great distance, which some of them had run in the earth, after they had been sufficiently heated. They therefore maintained, that those waters particularly termed _acidulæ_ (the greatest part of which are impregnated with iron), or those, which, tho’ intensely cold, contained a large proportion of mineral matter, had in some part of the earth been impregnated with it, by means of an intense heat, which they had been gradually deprived of by a long passage thro’ the colder parts of the earth. Some naturalists again, of a later date, having exploded the former notion as chimerical, have thought, that a vapour rising from vitriolic minerals, and mixed with the neighbouring streams of water in the bowels of the earth, has imbued them with some of the parts, and with the properties, of vitriol.
Others are of opinion, that the exhalations of vitriolic minerals, passing thro’ the cavities of the earth, are there condensed by the subterraneous cold into a limpid fluid, containing the very finest parts of that mineral salt: which fluid, mixing with the præterlabent streams of water, and issuing out of the earth with them, produce those mineral springs called vitriolic. The last opinion I shall mention on this subject, and which indeed appears the most plausible, is of those, who think, that the iron is corroded and dissolved in these waters by means of an acid: for, as they imagine simple water incapable of doing this, they suppose, that it is first imbued with an acid in the bowels of the earth; and then, by the corrosion of the chalybeat minerals, thro’ which it runs, it comes to be impregnated with them. I once received this opinion, as the most probable I could then observe, concerning the origin of these springs: yet not as being satisfactory; for there are many objections against it, which it is difficult either to elude or to answer. The supposition of an acidity in ferrugineous waters, I thought but ill confirmed, because, upon trial, they discover no vestiges of it, but rather appear to be alkaline. Besides, in considering the causes of mineral waters, it seems more probable, that whatever minerals they contain, they must be such, as can be received or extracted by common water in its passage thro’ the earth, by solution, abrasion, or the like simple operations; and in this way alone I think we may come to account not only for the commixtion of the saline and terrene minerals, which are found in medical waters, but likewise of those, that are metalline or sulphureous; for which simple water, at first sight, may perhaps seem to be an insufficient solvent.
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