which has this Peculiarity, that in Cold weather it loſes its Fluidity and the greateſt part of its Tranſparency, and looks like a White or Whitiſh Oyntment, and near at hand ſeems to conſiſt of a Multitude of little ſoft Scales: Of this Coagulated Stuff we ſpread a little with a Knife upon a piece of White Paper, and letting fall on it, and mixing with it a drop or two of Oyl of Vitriol, immediately (as we fore-ſaw) there emerg'd together with ſome Heat and Smoak, a Blood-Red Colour, which therefore was in a trice produc'd by two Bodies, whereof the one had but a Whitiſh Colour, and the other (if carefully rectify'd) had no Colour at all.
EXPERIMENT XXXVI.
But on this Occaſion (Pyrophilus) we muſt add once for all, that in many of the above-recited Experiments, though the changes of Colour happen'd as we have mention'd them: yet the emergent or produc'd Colour is oft times very ſubject to Degenerate, both quickly and much. Notwithſtanding which, ſince the Changes, we have ſet down, do happen preſently upon the Operation of the Bodies upon each other, or at the times by us ſpecify'd;
that is ſufficient both to juſtifie our Veracity, and to ſhew what we Intend; it not being Eſſential to the Genuineneſs of a Colour to be Durable. For a fading Leaf, that is ready to Rot, and moulder into Duſt, may have as true a Yellow, as a Wedge of Gold, which ſo obſtinately reſiſts both Time and Fire. And the reaſon, why I take occaſion from the former Experiment to ſubjoyn this general Advertiſement, is, that I have ſeveral times obſerv'd, that the Mixture reſulting from the Oyls of Vitriol, and of Anniſeeds, though it acquire a thicker conſiſtence than either of the Ingredients had, has quickly loſt its Colour, turning in a very ſhort time into a dirty Gray, at leaſt in the Superficial parts, where 'tis expos'd to the Air; which laſt Circumſtance I therefore mention, becauſe that, though it ſeem probable, that this Degeneration of Colours may oft times and in divers caſes proceed from the further Action of the Saline Corpuſcles, and the other Ingredients upon one another, yet in many caſes much of the Quick change of Colours ſeems aſcribeable to the Air, as may be made probable by ſeveral reaſons: The firſt whereof may be fetcht from the newly recited Example of the two Oyls; The next may be, that we have ſometimes obſerv'd
long Window-Curtains of light Colours, to have that part of them, which was expos'd to the Air, when the Window was open, of one Colour, and the lower part, that was ſheltred from the Air by the Wall, of another Colour: And the third Argument may be fetch'd from divers Obſervations, both of others, and our own; For of that Pigment ſo well known in Painters Shops, by the name of Turnſol, our Induſtrious Parkinſon, in the particular account he gives of the Plant that bears it, tells us alſo, That the Berries when they are at their full Maturity, have within them between the outer Skin and the inward Kirnel or Seed, a certain Juice or Moiſture, which being rubb'd upon Paper or Cloath, at the first appears of a freſh and lovely Green Colour, but preſently changeth into a kind of Blewiſh Purple, upon the Cloath or Paper, and the ſame Cloath afterwards wet in Water, and wrung forth, will Colour the Water into a Claret Wine Colour, and theſe (concludes he) are thoſe Raggs of Cloath, which are uſually call'd Turnſol in the Druggiſts or Grocers Shops[a]21]. And to this Obſervation of our Botanist we will add an Experiment of our own, (made before we met with That) which, though in many Circumſtances, very
differing, ſerves to prove the ſame thing; for having taken of the deeply Red Juice of Buckthorn Berries, which I bought of the Man that uſes to ſell it to the Apothecaries, to make their Syrrup de Spina Cervina, I let ſome of it drop upon a piece of White Paper, and having left it there for many hours, till the Paper was grown dry again, I found what I was inclin'd to ſuſpect, namely, That this Juice was degenerated from a deep Red to a dirty kind of Greyiſh Colour, which, in a great part of the ſtain'd Paper ſeem'd not to have ſo much as an Eye of Red: Though a little Spirit of Salt or diſſolv'd Alcaly would turn this unpleaſant Colour (as formerly I told you it would change the not yet alter'd Juice) into a Red or Green. And to ſatisfie my ſelf, that this Degeneration of Colour did not proceed from the Paper, I drop'd ſome of the deep Red or Crimſon Juice upon a White glaz'd Tile, and ſuffering it to dry on there, I found that ev'n in that Body, on which it could not Soak, and by which it could not be Wrought, it nevertheleſs loſt its Colour. And theſe Inſtances (Pyrophilus) I am the more carefull to mention to you, that you may not be much Surpris'd or Diſcourag'd, if you ſhould ſometimes miſs of performing
punctually what I affirm my ſelf to have done in point of changing Colours; ſince in theſe Experiments the over-ſight or neglect of ſuch little Circumſtances, as in many others would not be perhaps conſiderable, may occaſion the mis-carrying of a Trial. And I was willing alſo to take this occaſion of Advertiſing you in the repeating of the Experiments mention'd in this Treatiſe, to make uſe of the Juices of Vegetables, and other things prepar'd for your Trials, as ſoon as ever they are ready, leſt one or other of them grow leſs fit, if not quite unfit by delay; and to eſtimate the Event of the Trials by the Change, that is produc'd preſently upon the due and ſufficient Application of Actives to Paſſives, (as they ſpeak) becauſe in many caſes the effects of ſuch Mixtures may not be laſting, and the newly produc'd Colour may in a little time degenerate. But, (Pyrophilus) I forgot to add to the two former Obſervations lately made about Vegetables, a third of the ſame Import, made in Mineral ſubſtances, by telling you, That the better to ſatisfie a Friend or two in this particular, I ſometimes made, according to ſome Conjectures of mine, this Experiment; That having diſſolv'd good Silver in Aqua-fortis, and Precipitated it with Spirit of Salt, upon
the firſt Decanting of the Liquor, the remaining Matter would be purely White; but after it had lain a while uncover'd, that part of it, that was Contiguous to the Air, would not only loſe its Whiteneſs, but appear of a very Dark and almoſt Blackiſh Colour, I ſay that part that was Contiguous to the Air, becauſe if that were gently taken off, the Subjacent part of the ſame Maſs would appear very White, till that alſo, having continu'd a while expos'd to the Air, would likewiſe Degenerate. Now whether the Air perform theſe things by the means of a Subtile Salt, which we elſewhere ſhow it not to be deſtitute of, or by a peircing Moiſture, that is apt eaſily to inſinuate it ſelf into the Pores of ſome Bodies, and thereby change their Texture, and ſo their Colour; Or by ſolliciting the Avolation of certain parts of the Bodies, to which 'tis Contiguous; or by ſome other way, (which poſſibly I may elſewhere propoſe and conſider) I have not now the leiſure to diſcourſe. And for the ſame reaſon, though I could add many other Inſtances, of what I formerly noted touching the emergency of Redneſs upon the Digeſtion of many Bodies, inſomuch that I have often ſeen upon the Borders of France (and probably we may have the like in
England) a ſort of Pears, which digeſted for ſome time with a little Wine, in a Veſſel exactly clos'd, will in not many hours appear throughout of a deep Red Colour, (as alſo that of the Juice, wherein they are Stew'd, becomes) but ev'n on pure and white Salt of Tartar, pure Spirit of Wine, as clear as Rock-water, will (as we elſewhere declare) by long Digeſtion acquire a Redneſs; Though I ſay ſuch Inſtances might be Multiply'd, and though there be ſome other Obvious changes of Colours, which happen ſo frequently, that they cannot but be as well Conſiderable as Notorious; ſuch as is the Blackneſs of almoſt all Bodies burn'd in the open Air: yet our haſte invites us to reſign you the Exerciſe of enquiring into the Cauſes of theſe Changes. And certainly, the reaſon both why the Soots of ſuch differing Bodies are almoſt all of them all Black, why ſo much the greater part of Vegetables ſhould be rather Green than of any other Colour, and particularly (which more directly concerns this place) why gentle Heats do ſo frequently in Chymical Operations produce rather a Redneſs than another Colour in digeſted Menſtruums, not only Sulphureous, as Spirit of Wine, but Saline, as Spirit of Vinegar, may be very well worth
a ſerious Inquiry; which I ſhall therefore recommend to Pyrophilus and his Ingenious Friends.