Among the Experiments that tend to ſhew that the change of Colours in Bodies may proceed from the Vary'd Texture of their Parts, and the conſequent change of their Diſpoſition to Reflect or Refract the Light, that ſort of Experiments muſt not be left unmention'd, which is afforded us by Chymical Digeſtions. For, if Chymiſts will believe ſeveral famous Writers about what they call the Philoſophers Stone, they muſt acknowledge that the ſame Matter, ſeald up Hermetically in a Philoſophical Egg, will by the continuance of Digeſtion, or if they will have it ſo (for it is not Material in our caſe which of the two it be)
of Decoction, run through a great Variety of differing Colours, before it come to that of the Nobleſt Elixir; whether that be Scarlet, or Purple, or what ever other Kind of Red. But without building any thing on ſo Obtruſe and Queſtionable an Operation, (which yet may be pertinently repreſented to thoſe that believe the thing) we may obſerve, that divers Bodies digeſted in carefully-clos'd Veſſels, will in tract of time, change their Colour: As I have elſewhere mention'd my having obſerv'd ev'n in Rectify'd Spirit of Harts-horn, and as is evident in the Precipitations of Amalgams of Gold, and Mercury, without Addition, where by the continuance of a due Heat the Silver-Colour'd Amalgam is reduc'd into a ſhining Red Powder. Further Inſtances of this Kind you may find here and there in divers places of my other Eſſays. And indeed it has been a thing, that has much contributed to deceive many Chymiſts, that there are more Bodies than one, which by Digeſtion will be brought to exhibit that Variety and Succeſſion of Colours, which they imagine to be Peculiar to what they call the True matter of the Philoſophers. But concerning this, I ſhall referr you to what you may elſewhere find in the Diſcourſe written touching the
paſſive Deceptions of Chymiſts, and more about the Production of Colours by Digeſtion you will meet with preſently. Wherefore I ſhall now make only this Obſervation from what has been deliver'd, That in theſe Operations there appears not any cauſe to attribute the new Colours emergent to the Action of a new Subſtantial form, nor to any Increaſe or Decrement of either the Salt, Sulphur, or Mercury of the Matter that acquires new Colours: For the Veſſels are clos'd, and theſe Principles according to the Chymiſts are Ingenerable and Incorruptible; ſo that the Effect ſeems to proceed from hence, that the Heat agitating and ſhuffling the Corpuſcles of the Body expos'd to it, does in proceſs of time ſo change its Texture, as that the Tranſpoſed parts do Modifie the incident Light otherwiſe, than they did when the Matter appear'd of another Colour.
EXPERIMENT XXXI.
Among the ſeveral changes of Colour, which Bodies acquire or diſcloſe by Digeſtion, it it very remarkable, that Chymiſts find a Redneſs rather than any other Colour in moſt of the Tinctures they Draw, and ev'n in the more Groſs Solutions they
make of almoſt all Concretes, that abound either with Mineral or Vegetable Sulphur, though the Menſtruum imploy'd about theſe Solutions or Tinctures be never ſo Limpid or Colourleſs.
This we have obſerv'd in I know not how many Tinctures drawn with Spirit of Wine from Jalap, Guaicum, and ſeveral other Vegetables; and not only in the Solutions of Amber, Benzoin, and divers other Concretes made with the ſame Menſtruum, but alſo in divers Mineral Tinctures. And, not to urge that familiar Inſtance of the Ruby of Sulphur, as Chymiſts upon the ſcore of its Colour, call the Solution of Flowers of Brimſtone, made with the Spirit of Turpentine, nor to take notice of other more known Examples of the aptneſs of Chymical Oyls, to produce a Red Colour with the Sulphur they extract, or diſſolve; not to inſiſt (I ſay) upon Inſtances of this nature, I ſhall further repreſent to you, as a thing remarkable, that, both Acid and Alcalizate Salts, though in moſt other caſes of ſuch contrary Operations, in reference to Colours, will with many Bodies that abound with Sulphureous, or with Oyly parts, produce a Red; as is manifeſt partly in the more Vulgar Inſtances of the Tinctures, or Solutions of
Sulphur made with Lixiviums, either of Calcin'd Tartar or Pot-aſhes, and other Obvious examples, partly by this, that the true Glaſs of Antimony extracted with ſome Acid Spirits, with or without Wine, will yield a Red Tincture, and that I know an Acid Liquor, which in a moment will turn Oyl of Turpentine into a deep Red. But among the many Inſtances I could give you of the eaſie Production of Redneſs by the Operation of Saline Spirit, as well as of Spirit of Wine; I remember two or three of thoſe I have tried, which ſeem remarkable enough to deſerve to be mention'd to you apart.
EXPERIMENT XXXII.
But before we ſet them down, it will not perhaps appear impertinent to premiſe;