CHAP. II.
In which is shewed, that by the Solution of Salts in Water, some certain space, more or less, is gained. That the space is different according to the Nature of the Salt. And what the just space is, which is gained.
HE Fifth Enquiry is, Whether by dissolving of a Salt in Water, there be any space gained, or not. That is, whether the Bulk of the Water be greater before the Salt lying in it be fully dissolved, than afterwards. For tryal whereof, I took a Bolt-head with a slender Neck, holding somewhat more than a pint; and filling it up to a certain place in the Neck; I then put in an Ounce or two of Salt. And observing the hight of the Water, both before it was dissolved, and afterwards; It plainly appeared, that there was some, and that a considerable space, gained by the Dissolution; the Water thereby sinking several Inches below the place, where it stood after the Salt was first put into it.
2. §. From this Experiment it is plain, that there are Vacuities in Water. That is to say, that all the parts of Water are not contiguous, but that either betwixt, or in the Atomes of the Water themselves, there are certain Pores, either absolutely void, or at least filled up with another more subtile body which is easily excluded by the particles of Salt: by possessing the room of which the above said space is gained.
3. §. The Sixth Enquiry is, Whether the space be equally gained, by an equal encrease of the same Salt.
4. §. For this I made two tryals; the first was this. Two half Ounces of Salt Armoniac, being successively dissolved in the same Water; both of them raised up the Water in the Neck of the Bolt-head, equally; the first 3 Inches ⅝, and so the second.
5. §. The other was this. Four half Ounces of Nitre, being successively dissolved in the same Water, they all of them raised up the Water in the Neck of the Bolt-head, equally; the first a little above two Inches, and the 2ᵈ, 3ᵈ, and 4ᵗʰ, just as much.
6. §. The Seventh Enquiry is, Whether upon the Dissolution of several kinds of Salts, be gained so many several quantities of space. For this I made tryal upon Eleven several Salts, sc. Salt of Tartar, Common Salt, Sal Gemmeus, Roman Vitriol, Nitre, White Vitriol, Green Vitriol, Alum, Borax, Loaf-Sugar, and Sal Armoniac; of all which, I dissolved an equal quantity sc. two Ounces, in an equal quantity of Water, severally; that is, taking fresh Water for every Solution. The success was, That the Sal Armoniac raised the Water 15 Inches. The Loaf-Sugar, 13 Inches and ⅜ᵗʰˢ· The Borax, a Foot. The Alum 11 Inches, and ⅝ᵗʰˢ. Green Vitriol, 9 Inches and ⅝ᵗʰˢ· White Vitriol, 9 Inches and ⅛ᵗʰ. Nitre, 8 Inches, and ⅜ᵗʰˢ· Roman Vitriol, 7 Inches and ⅝ᵗʰˢ· Sal Gemmæ, 6 Inches, and ⅝ᵗʰˢ· Common Salt, 6 Inches and ⅜ᵗʰˢ· Salt of Tartar, not above 4 Inches and ⅛ᵗʰ. All which differences are plain, and most of them very remarquable: Two Ounces of Sal Armoniac raising the Water near four times as high, as the same quantity of Salt of Tartar.
7. §. From this and the fourth Experiment, compared, it also appears, That the several spaces gained by the several Salts, though sometimes they do, yet do not always answer to the Solubility of the said Salts. As to give some Instances; Loaf-Sugar is the most dissoluble of any other Salt; yet it gaineth less space than all the rest, save only Sal Armoniac. So Green Vitriol is more dissoluble then either Nitre or Common Salt; yet gaineth less space than either, especially than the latter. And Sal Armoniac, which is more dissoluble than Alum or Borax, yet gaineth less space than either of them. The Cause whereof is not easily assigned.
8. §. Note also, that by the same Experiment, as well as by the Taste and other Circumstances, it is plain, That Sal Gemmæ is nothing else but Common Salt, coagulated or Crystalliz’d under Ground.
9. §. Again, as the Fifth Experiment sheweth, That there are Vacuities in Water: so doth this Last, that those Vacuities, are of differing kinds. Because, otherwise, it should seem, That the Bulk of the Water would increase, more or less, according to the Solubilitie of every Salt, and not be alternately differenced as it is; Some Salts, more dissoluble, increasing the Bulk of the Water less, and others less dissoluble, increasing it more. I say, that this difference dependeth not only upon the different Figures of the Atomes of Salt; because then every Salt which is more dissoluble, would (quantity for quantity) take up less room in the Water: which is contrary to the Experiment.
10. §. From the same Experiment, howsoever paradoxical it may seem, yet is it also manifest, That although Water be a Fluid, yet the Particles thereof are hard and consistent, and unalterable in their Figure. Otherwise it is plain, That all manner of Salts would be dissolved in the same manner, and take up the same room in the Water. For let the Figures of the Salts be never so various, yet if the Particles of Water were themselves Fluid or Inconsistent and Alterable, they would always so conforme to those Figures, as to fill up all Vacuities; and so upon the Solution of several Salts, if of equal quantity, the Water would still retein an equal Bulk. As suppose an Ounce of Iron were drawn into Wyer, another beaten into Plates, a third made into Hooks, a fourth into Needles, a fifth into Nails; every one of these five Ounces, being put severally into Water will encrease its Bulk equally. I conclude therefore, That the Atomes of Water are hard and unalterable.
11. §. The Eighth Enquiry was this, What that just space might be, which any Salt gaineth upon Dissolution, with respect to its own Bulk, or the Bulk of the Water? For the making of this Experiment, Water will not serve, nor yet Spirit of Wine; because they both of them dissolve more or less of those Salts which are put into them; whereby the observation of the true Bulk of the Salt, and consequently of the just space it gaineth by Dissolution is lost. I took therefore Oyl of Turpentine, and pouring it into a Bolt-head, marked the place of its ascent in the Neck. Then pouring likewise into it two Ounces of Common Salt, I marked the second ascent of the Oyl; and found it to be 10 Inches and 6 eighths. Repeating the Experiment in like manner with two Ounces of Nitre, I found the ascent of the Oyl to be 11 Inches and ⅛ᵗʰ. Repeating it again with two Ounces of Alum, the ascent of the Oyl was 13 Inches and 2/8ᵗʰˢ· And making it once more with Sal Armoniac, the Oyl ascended to 15 Inches: the said several ascents of the Oyl being the true spaces which the Four abovesaid Salts take. From which, the space which the same Salts take up upon Dissolution, being deducted; the remainder is the space gained by that Dissolution. And so it appears, first, that Sal Armoniac gaineth nothing; being the only Salt of all I have tryed, which causeth the equal ascent both of the Water and the Oyl sc. just 15 Inches in both. Alum causeth the ascent of the Oyl to 13-2/8ᵗʰˢ, of the Water, to 11 Inches and ⅝ᵗʰˢ: So that it gains about 1 Inch and ½ out of 13. Nitre causeth the ascent of the Oyl, to 11 Inches and ⅛ᵗʰ; of the Water, to 8 Inches and ⅜ᵗʰˢ· So that Nitre by Dissolution gets almost the space of 3 Inches in 11. Common Salt causeth the ascent of the Oyl, to 10 Inches and 6/8ᵗʰˢ; of the Water, 6 Inches and ⅜ᵗʰˢ· So that Common Salt gains by Dissolution 4 Inches in 10, which is very considerable.
12. §. By this way the Specifick Gravity of all kinds of Salts may be easily taken, and the difference betwixt them is somewhat surprizing. For it appears by the Ascent of the Oyl, that Nitre, quantity for quantity, is about a 22ᵗʰ part lighter than Common Salt. Alum about a 6ᵗʰ part lighter. And Salt Armoniac, almost a 4ᵗʰ part lighter than Common Salt. The like estimate may be made of the Gravity of all other Salts.
13. §. By the same Experiment it also appears, That according to the Specifick Gravity of Salts they are many times at least more or less Volatile; as in the four last Salts is plain. For Common Salt which of all the four is the most fixed, is also the heavyest. Nitre which is somewhat less fixed is somewhat lighter. But Alum which is still less fixed is much lighter. And Sal Armoniac which is wholly Volatile, is the lightest of all the Salts above mentioned.