WATER, in physiology, a clear insipid and colourless fluid, coagulable into a transparent solid substance at 32° of Fahrenheit's thermometer, and volatile in every degree of heat above that. Many different kinds of waters are commonly spoken of, such as Chalybeate waters, sulphureous, saline, putrid waters, &c. but all these differ from one another only in having various substances mixed with them, from which when perfectly freed, the water is always the same; so that it has not improperly been reckoned one of the four elements.
The general and most effectual method of freeing water from any heterogeneous substance is distillation. Thus it may be perfectly purified from almost every saline substance whatever; and thus sea-water may be rendered perfectly fresh and wholesome. It must be observed, however, that all distilled water acquires an empyreumatic smell and taste by this operation; so that it makes but disagreeable drink until it has stood for some time. Another disadvantage which attends water when newly distilled, is its want of fixed air; which, however, it soon recovers by exposure to the air for some time. If water is actually putrid, it cannot be made fit for use by simple distillation. In this case a quantity of lime is necessary, which extracts a volatile alkali, but destroys the putrid substance. After the water is once distilled in this manner, it may be more fully purified by adding some vitriolic or other acid to neutralise the alkali, and redistilling it with this addition. The substance from which it is most difficult to free water is any volatile oil. This rises in distillation, and will also pass through every kind of strainer. The only cure in this case therefore is to expose the fluid for a considerable time to the air, when the oil will fly off or become effete and fixed, so that it cannot rise in distillation; after which the water may easily be purified.
Whether or not it is possible to convert water into earth, is a question which has much engaged the attention of philosophers. Mr Boyle relates, that a friend of his, by distilling a quantity of water an hundred times, found at length, that he had got six-tenths of the first quantity in earth: whence he concludes, that the whole water, by further prosecuting the operation, might be converted into earth. Others have made experiments to the same purpose, and seemingly with the same success; but the deception is now found out. Water has the power of corroding the hardest bodies, even glass itself, by long digestion, especially when assisted by heat; and hence those who have made the experiments just mentioned have been themselves deceived, by supposing the earth which really came from the containing vessel to come from the water.
It is surprising to consider the plenteous stock of water which even dry bodies afford. Hartshorn kept forty years, and turned as hard and dry as any metal, so that if struck against a flint it will yield sparks of fire; yet being put into a vessel, and distilled, will afford one-eighth part of its quantity of water. Bones dead and dried 25 years, and thus become almost as hard as iron; yet, by distillation, have afforded half their weight of water. And the hardest stones, ground and distilled, do always discover a portion thereof.
From considerations of this kind, Thales, and some other philosophers, have been led to hold, that all things were made of water; which opinion, probably, had its rise from the writings of Moses, where he speaks of the spirit of God moving upon the face of the waters: But Mr Boyle does not conceive the water here mentioned by Moses as the universal matter, to be our elementary water: we need only suppose it an agitated congeries of a great variety of seminal principles, and of other corpulesces fit to be subduced and fashioned by them; and it may yet be a body fluid like water, in case the corpulesces it was made up of were by their
Creator made small enough, and put into such an actual motion as might make them roll and glide easily over one another. However, Basil Valentine, Paracelsus, Van Helmont, Sendivogius, and others, have maintained the same principle, viz. that water is the elemental matter or flamen of all things, and suffices alone for the production of all the visible creation. Thus Sir Isaac Newton, "All birds, beasts, and fishes, insects, trees, and vegetables, with their several parts, do grow out of water, and watery tinctures, and salts; and, by putrefaction, return again to watery substances."
Helmont endeavours to prove this doctrine from an experiment; wherein, burning a quantity of earth till all the oil was consumed, and then mixing it up with water to draw out all the salt; and putting this earth, thus prepared, into an earthen pot, which nothing but rain-water could enter; yet a willow, planted therein, grew up to a considerable height and bulk, without any sensible diminution of the earth: whence he concluded, that the water was the only nutriment of the vegetable kind, as vegetables are of the animal. The same thing is inferred by Mr Boyle, from a parallel experiment: and the whole is countenanced by Sir Isaac Newton, who observes, that water, standing a few days in the open air, yields a tincture, which, like that of malt, by standing longer, yields a sediment, and a spirit; but before putrefaction, is fit nourishment for animals and vegetables.
But Dr Woodward endeavours to show the whole a mistake: water containing extraneous corpulesces, some of these, he shows, are the proper matter of nutrition; the water being still found to afford so much the less nourishment the more it is purified by distillation. Thus a plant in distilled water will not grow so fast as in water not distilled; and if the water be distilled three or four times over, the plant will scarce grow at all, or receive any nourishment from it. So that water, as such, does not seem the proper nutriment of vegetables, but only the vehicle thereof, which contains the nutritious particles, and carries them along with it through all the parts of the plant. See AGRICULTURE, sect. i. ii.
No standard for the weight and purity of water.—Water scarce ever continues two moments exactly of the same weight, by reason of the air and fire contained therein. Thus, a piece of pure limpid ice, laid in a nice balance, never continues in equilibrio. In effect, the expansion of water in boiling, shows what effect the different degree of fire has, on the gravity of water. This makes it difficult to fix the specific gravity of water, in order to settle its degree of purity; but this we may say in the general, that the purest water we can procure, is that which is 880 times as heavy as air. However, neither have we any tolerable standard in air: for, water being so much heavier than air, the more water is contained in the air, the heavier of course must it be; as, in effect, the principal part of the weight of the atmosphere seems to arise from the water.
Property and effects of water.—Water is found the most penetrative of all bodies, after fire, and the most difficult to confine; so that a vessel through which water cannot pass may retain any thing. Nor is it any objection, that syrups and oils will sometimes pass through
through bodies which will hold water; this not being owing to the greater subtlety and penetration of their particles, but to the resin wherewith the wood of such vessels abounds, to which oils and syrups are as menstrua; so that, dissolving the resin, they make their way through the spaces left thereby: whereas water, not acting on resin, is retained.
And yet water gradually makes its way even through all woods, and is only retainable in glass and metals; nay, it was found by experiment at Florence, that when shut up in a spherical vessel of gold, and then violently pressed with a huge force, it made its way through the pores even of the gold: so that the most solid body in nature is permeable to water.
Water has been supposed more fluid than air; a body being reputed more fluid than another, when its parts will find way through smaller pores: now air, it is known, will not pass through leather, as is evident in the case of an exhausted receiver covered therewith; whereas water passes with ease. Again, air may be retained in a bladder, but water oozes through. In effect, it is found, that water will pass through pores ten times smaller than air will. M. Homberg, however accounts for this passage of water through the narrow pores of animal substances which will not admit the air, on another principle, viz. its moistening and dissolving the glutinous matter of the fine fibres of the membranes, and rendering them more pliable and distensible; which the air, for want of a wetting property, cannot do. As a proof of this doctrine, he filled a bladder, and compressed it with a stone, and found no air to come out; but placing the bladder thus compressed in water, the air easily escaped.
This property of water, joined with its smoothness and lubricity, fits it to serve as a vehicle for the commodious and easy conveyance of the nutritious matter of all bodies: being so fluid, and passing and repassing so readily, it never stops up the pores, but leaves room for the following water to bring on a new supply of nutritious matter. And yet the same water, as little cohesive as it is, and as easily separated from most bodies, according to some is the principle of union in a great number of bodies, and binds them together into the most solid masses. Water, we see, mixed up with earth or ashes, gives them the utmost firmness and fixity. The ashes, e. gr. of an animal, incorporated with pure water into a paste, and baked with a vehement fire, grow into a coppel; which is a body remarkable for this, that it will bear the utmost effort of a refiner's furnace. It is, in effect, upon the glutinous nature of water alone that our houses stand: for take but this out of wood, and it becomes ashes; or out of tiles, and they become dust. Thus, a little clay dried in the sun, becomes a powder, which, mixed with water, sticks together again, and may be fashioned at pleasure; and this dried again by a gentle fire, or in the sun, and then baked in a potter's oven by an intense fire, becomes little other than a stone. It cannot however be proved that the small quantity of water supposed to remain in bricks, &c. is the cause of their cohesion. It seems more probable that an incipient vitrification is the reason why bricks and earthen ware of all kinds stick together. Some of these, porcelain and stone ware in particular, are evidently vitrified.
For a long time water was supposed to be incompressible, or incapable of being, by any force whatever, reduced into a less compass. This was thought to be demonstrated by the famous experiment above-mentioned, made by order of the great duke of Tuscany. The water being incapable of condensation, rather than yield, translated through the pores of the metal, so that the ball was found wet all over the outside; till at length making a cleft in the gold, it sprung out with great vehemence. From this last circumstance, indeed, some have weakly concluded it was elastic. For the impetus wherewith the water darted forth, was more probably owing to the elasticity of the gold, which communicated that impression to the water.—Of late, however, the contrary opinion has been adopted; and Mr Canton has made some experiments to show, that water not only may be, but actually is, compressed, by the weight of the atmosphere. These we shall relate in his own words. "Having procured a small glass-tube of about two feet in length, with a ball at one end of it of an inch and a quarter in diameter, I filled the ball and part of the tube with mercury; and keeping it with a Fahrenheit's thermometer in water which was frequently stirred, it was brought exactly to the heat of ; and the place where the mercury stood in the tube, which was about inches above the ball, was carefully marked. I then raised the mercury by heat to the top of the tube, and sealed the tube hermetically; and when the mercury was brought to the same degree of heat as before, it stood in the tube of an inch higher than the mark.
"The same ball, and part of the tube, being filled with water exhausted of air instead of the mercury, and the place where the water stood in the tube when it came to rest in the heat of being marked, which being sealed six inches above the ball, the water was then raised by heat till it filled the tube; which being sealed again, and the water brought to the heat of as before, it stood in the tube of an inch above the mark.
"Now the weight of the atmosphere (or about 73 pounds averdupois) pressing on the outside of the ball and not on the inside, will squeeze it into less compass. And by this compression of the ball the mercury and water will be equally raised in the tube: but the water is found, by the experiments above related, to rise of an inch more than the mercury, by removing the weight of the atmosphere.
"In order to determine how much water is compressed by this or a greater weight, I took a glass ball of about an inch and in diameter, which was joined to a cylindrical tube of four inches and in length, and diameter about of an inch; and by weighing the quantity of mercury that exactly filled the whole length of the tube, I found that the mercury in of an inch of the tube, was the 100,000th part of that contained in the ball; and with the edge of a file I divided the tube accordingly.
"This being done, I filled the ball and part of the tube with water exhausted of air; and left the tube open, that the ball, whether in rarefied or condensed air, might always be equally pressed within and without, and therefore not altered in its dimensions. Now by placing this ball and tube under the receiver of an air-pump, I could see the degree of expansion of the water
Water. water answering to any degree of rarefaction of the air; and by putting it into a glass receiver of a condensing engine, I could see the degrees of compression of the water answering to any degree of condensation of the air. But great care must be taken in making these experiments, that the heat of the glass ball be not altered, either by the coming on of moisture, or its going off by evaporation; which may easily be prevented by keeping the ball under water, or by using oil only in working the pump and condenser.
"In this manner, I have found by repeated trials, when the heat of the air has been above 50°, and the mercury at a mean height in the barometer, that the water will expand and rise in the tube by removing the weight of the atmosphere four divisions and ; or one part in 21,740; and will be as much compressed under the weight of an additional atmosphere. Therefore the compression of water by twice the weight of the atmosphere, is one part in 10,870 of its whole bulk.
"The famous Florentine experiment, which so many philosophical writers have mentioned as a proof of the incompressibility of water, will not, when carefully considered, appear sufficient for that purpose: for in forcing any part of the water contained in a hollow globe of gold through its pores by pressure, the figure of the gold must be altered, and consequently the internal space containing the water diminished; but it was impossible for the gentlemen of the academy del Cimento to determine, that the water which was forced into the pores and through the gold, was exactly equal to the diminution of the internal space by the pressure."
An easy confirmation of this doctrine of Mr Canton's would be, to fill a vial exactly with water taken up at a great depth, by a person in a diving bell. If the water at that depth was really compressed by what lay above it, it must expand during its ascent to the surface, and either break the vial, or drive out the stopper.