The works of the Honourable Robert Boyle, Esq., epitomiz'd by Richard Boulton ... ; illustrated with copper plates.

CHAP. VII. Of the Porousness of solid Bodies.

* 1.1THAT even solid Bodies are not desti∣tute of Pores, I am inclined to be∣lieve, because most solid Bodies, as Gems, &c. have once been in fluid Forms; and since Flu∣ids are generally made up of Particles of a determinate size and shape, they must needs leave some Pores betwixt them.

Another Reason why I am inclined to think most Bodies porous, is their specific gravity; which would not vary were the Parts of them equally compressed and closed

together, but since Copper is heavier than Iron and Gold, as nineteen to one to its pro∣portion of Water, and Copper only as nine to one, it must follow, that the matter of Iron possesses as much space again as Gold and more. And tho' hardness is urged by some as an Argument of their Substance being condensed, yet I have elsewhere shewn, that tho' Diamonds are the hardest Bodies, they are far from be∣ing the heaviest, which is the only sign whether they be condensed or not.

And since Metals themselves are made up of a Coalition of several Parts, it is impossi∣ble they should be so Physically adapted, as to∣tally implere spatium; since were Cubes made of Marble, it is impossible they should be so exactly Polished as every where to be con∣tiguous, since the Bodies employed to Polish them are observed to make little furrows up∣on them, and consequently leave little Inter∣vals or Pores.

And that Wood is not void of Pores will appear, since Quick-silver hath been observed to penetrate the sides of a hollow Cylindrical piece of Wood, and when the Air was drawn out of my Pneumatical Instrument, the exter∣nal pressed so hard upon the outside of a Board which covered it, that tho' it was of strong Wood, and of a considerable thickness, yet it made its way into the Cavity of the Re∣ceiver, through the Pores of the Wood; and to these Instances I shall add, that the fumes of a Smoaking Liquor tinged a Copper Half-penny, through a broad thin shaving of Deal, tho' we could not discover any sensible Per∣foration;

and the same Experiment being a∣gain repeated with two, and a third with three shavings, they tinged the Copper Half-penny, tho' not in so little time, nor quite so conspi∣cuously. And,

That baked Clay is not void of Pores is evident, since Oyl will soak through strong and well baked Earthen Vessels, and so will Solutions of Nitre and some other Salts; and very few except Hassian Crucibles will keep Salt of Tartar long in Fusion without being penetrated by them. And Vitriol and Salt-Petre have been observed to lose much of their weight when distilled in Earthen Vessels, the subtle and spirituous Parts flying away through their Pores. And I am told, that those Juggs that are made of Earth, hardened suffi∣ciently to strike fire with a good Stell, have their Pores pervaded by the most subtle Parts of Spirituous Liquors; and it hath been found by Experience, that Spirituous Cyder hath sweat through the sides of Stone Bottles; which manifested it self by its taste: And I have found, that Silver dissolved and turned into a horny Substance with Aqua Fortis, be∣ing kept in Fusion in an Hassian Crucible, se∣veral Particles penetrated the Pores of it, and appeared on the outside.

And to prove that natural Stones are po∣rous, I shall intimate, that I had a Vessel made of Stone sent from the West-Indies, through whose Pores Water would sweat; and if the Transparency or Opacity of Bodies proceeds from a rectitude or crookedness of Pores, which makes them fit or unfit to transmit the Rays

of Light, Oculus Mundi will be an Argument of the Porosity of Stones; since whilst it is dry and in the Air it is opacous, but when it hath lain a while in the Water it becomes trans∣parent like Amber, but soon loses its Diapha∣neity when exposed to the Air again, and so Paper wet with Water becomes more transpa∣rent, but loses of that Transparency when dry∣ed again; and to favour this explication, I shall add, that an Oculus Mundi having been weigh∣ed after it was taken out of the Water, it ap∣peared to be heavier than before. And since several Stones, as Granates, Emeri, &c. con∣tain Mineaal Parts, it is impossible they should be exactly contiguous without leaving some Pores betwixt them and the Parts of the Stone; and for the like Reason all artificial Gems made by Fusion, and tinged with Heteroge∣neous Pigments must be supposed to be fur∣nished with Pores; and since natural Gems are made up of Stony Ingredients, and Mine∣ral Parts, for the same Reason we must suppose them to be furnished with Pores likewise; and the like may be concluded in reference to all Heterogeneous and compound Substances; as Marcasites, Load-Stones, &c. And that white Marble is not void of pores may be argued not only from its easie Solution by Aqua For∣tis, Spirit of Salt, &c. but from its aptness to be tinged with Vapours, that are not fretting, so that red and other colours may be soaked into it as Oyl is into Wood. And having ce∣mented some clear Fragments of native Cry∣stal with a composition of some Volatile Mi∣nerals, together with a Salt or two, and hav∣ing

suffered the Crucibles to cool leisurely, se∣veral of the Fragments were stained here and there with different colours, some more and o∣thers less dull; but whether the Tincture these pieces of Crystal received proceeded from some of the finest of the Mineral Parts, imbi∣bed into the Stone when flawed with too much haste; and whether upon cooling those flaws did not grow too close to be discernable to the Eye, I shall not determine, but shall add, that it hath been observed, that Rubies when Po∣lished upon the Wheel, and very hot, have seemed full of cracks, which upon their cool∣ing wholly disappeared.

And that Metals themselves are porous may be argued, from their aptness to be dissolved in proper Menstruums. And especially by lay∣ing Sulphur and thin Plates of Copper SSS, in a Crucible upon which another was luted, to keep the Sulphur from taking fire; for having kept them thus about three hours in a heat, which was sufficient to melt the Sulphur, but not the Metal, when it was taken away from the fire and cooled, we found, that the Sulphur had so penetrated the Body of the Copper as to turn most of it into a brittle Substance, which would crumble away with ones fingers, being altered not only in Texture but colour, some being of a dirty dark colour, others of a violet, and many of the Plates when they were broken, seemed to have been divided into two Plates, and to have a manifest distance betwixt them, and we could likwise discern the fibers of the Metal, extend themselves from one side of the Copper Plates to the other. And that the Sul∣phur

penetrated into the Pores of the Cop∣per-Plates might not only be discerned by their increase of weight, and bulk, but a Blue Flame which would discover it self when they were laid upon quick Coles. And by a like Experiment, we found that the Body of Sil∣ver, Tin, and Lead, might be penetrated. And not only Sulphur, but Arsnick will pe∣netrate thus into the Body of Metals. And I know a Pigment which tinged the Body of Copper, so as to give it the Colour of Gold: And Perfumes do not only continue long in the Pores of Glasses; but I am told by one, that he had a Watch, whose Metal∣line Case was richly perfumed. And I re∣member I made a Substance much like Gold, which retained several Mercurial Particles in it, and being cast into a Ring, it was observed to have manifest Effects on the Eyes of several Persons. And I am told that the Off-spring of the Granadine Moors, had an Art of curiously perfuming the Weapons they forged; and the same Nobleman who told me this, acquainted me that he had a Fowling-piece whose Barrel was perfumed, but its smell was much fainter after it had been scou∣red.

And, Lastly, To shew that even common Glass is not void of Pores, I shall reduce what I have to say, and comprise it under the following Propositions.

PROP. I. It's very probable, that Glass may be pierced into, at some distance, even by visible and tangible Bodies.

And besides the Arguments already offered to evince the porosity of Bodies, I shall add, That a certain Spirit of Salt being kept in a Glass in a cool Place, it corroded some Parts so much as to leave them as thin as a piece of Paper; and lined with a white Substance, which seemed to be some of the Alkali of the Glass and Sand corroded by the Saline Spirits of the Menstruum, and coagulated with them into this odd kind of concrete; and this wrought no higher than the Liquor contained in the Glass. And besides this, I had another Vi∣al corroded by a distilled Liquor of Vitriol, which contained more Phlegm than Oyl; and to this Relation I shall add, That a Pound of Dantzick Vitriol, and a Pound of Sea-Salt, the one calcin'd lightly, and the other decrepita∣ted, being distilled in a well coated Retort, by degrees of Fire, giving at the last a very strong one; when the Vessel was taken off, we found that the Heat had here and there melted it; and that the Fluxed Caput Mor∣tuum had corroded the Glass, fetching off Films from it; and those Parts which did not appear to the Eye manifestly wasted; seem∣ed by their brittleness to have been penetra∣ted; so that their Texture was spoiled by the Saline and Vitriolate Particles.

PROP. II. Common Glass is not ordinarily permeable by Chymical Liquors, tho' strong and subtle, nor by the directly visible or odorable expirations of Bodies; tho' absolutely speaking, it is permea∣ble to some corporeal Substances.

And, First, It is manifest, not only that se∣veral Spirituous Liquors and Menstruums, may be kept in Glass Vessels without sweating through them, but even distilled in them; and I have found that neither Salt of Tartar would lent by being held in a Glass Bubble in the Water, nor would Sal-Armoniac penetrate it, so as to make its way out. But it is to be considered, that some Circumstances may vary these Ob∣servations, as when the Texture of Glass is too lax and open; or when the Bodies are vehe∣mently agitated with Heat, or are too subtile; and have a certain congruity with the Pores of the Glass. For I have seen a sort of Glass so soft, that not only hot Liquors, but moderate∣ly Corrosives would work upon it; and I have heard, that some sort of Glass is apt to be prejudiced by corrosive Liquors. And I was told by one, That he several times observ∣ed Gold to penetrate the Pores of Glass; and I have observ'd Fumes to make their way through the Pores of ordinary Glass, upon di∣stilling of Spirit of Harts-horn with a strong Fire.

And that the Pores of Glass are penetrated by some Substances, is evident, by the Effects

of Cold and Heat, on Bodies contained in seal∣ed Glasses; and that so gross a Body as the Ef∣fluviums of Earth will penetrate Glass, and work on Iron contained in it: And Light it self appears evidently to be contained in close∣ly sealed Glasses; and by a cantinued Heat, I have found the Parts of Fire to penetrate Glass, and add to the weight of Iron sealed up; and having tryed this Experiment with Filings of Copper, I found that their Colour was much altered, some of them being adorn∣ed with exceeding vivid Dyes; which they yet retain without being increased in weight, as if they were not able to stick themselves fast enough in the Pores of the Metal, to add to its Gravity. And I had a Liquor which would va∣ry its Colour, as if something in the Air was successively communicated to it, and receded again.

And to these, other Instances may be brought from what may be observed in painting Glass; for the Pigment being laid upon the Glass, and that placed upon a Bed of Lime, and then continued in a violent Heat, the Pores of the Class will be so opened, as either to im∣bibe the Parts of the Pigment, or to vitrifie and mix with it: And I have found, that by lay∣ing prepared Silver upon Glass, and placing that upon live Coals; when it was nealed a while, by giving it a sufficient degree of Heat, the Glass will acquire a Yellow, and almost a Golden Colour, which is not to be washed off; the way of preparing this Silver, is not al∣ways the same, the Glass-painters usually ad∣ding to it Antimony, Yellow Okre, or the like.

But since the Colour proceeds from the pene∣tration of the Silver into the Pores of the Glass; I usually make use of the Powder of Silver calcined, by burning Sulphur upon thin Plates; and I have often coloured Glass barely by the use of Leaves of Silver laid upon the surface of the Glass, and moistened with something to keep it from flying away. And I have often observed that tho' the Glass betwixt and the Light appeared Yellow, yet being held from it, it appeared Blue; which is a Confirmation of what we have inferred from the variation of Colours, in a Tincture of Lignum Nephri∣ticum; Viz. That they may be solved by Me∣charical Principles. And that the Colour of Glass tinged, proceeds from an Incorporation of the Parts of a Pigment with it, tho' they penetrate not the whole Substance, but tinge the superficies, (as I observed in Glass Plates, which were part of the Windows of St. Paul's Church before it was burnt) may be urged, since the Parts of the Silver may be wrought on by the fix'd Salts in the Glass, and afford different Colours, according to the difference of the Bo∣dies that work upon them, as Copper with Spi∣rit of Urine, give a deep Blue; with Spirit of Salt, a fair Green; and with Aqua Fortis, a Co∣lour partaking of both. And in making Glass of Lead, with Minium and White Sand, or Crystal, the Glass will be of an Amethystine Colour, but if you add a due proportion of calcin'd Copper, the Metal will give it a good Green; so as to pass for no bad E••ner••uld▪ and I remember, that distilling some Gold in a Retort, amalgamed with such Mercury as would

grow Hot with it in the Cold; the Matter did, before it flew away, perfectly stain an Inch in the Diameter of the bottom of the Glass, with a Colour, which, held from the Light, appeared like that of the better sort of Turquoises; but when interposed between the Window and the Eye, appeared of a some what Golden Colour. And Gold incorporated with Mercury, and kept in digestion, when the Fire was once very vehement, it burst the Vessel, and flew away, but tinged the lower part of the Glass quite through, with a glorious Red Colour, not inferior to that of Rubies.

Notes

• * 1.1

  Of the Po∣rousness of Solids.