Milks be suffer’d to stand unstirr’d for a convenient while, they are wont to let fall to the bottome a Resinous Substance, which the Spirit of Wine Diluted and Weakned by the Water pour’d into it was unable to support any longer.  And something of Kin to this change of Colour in Vegetables is that, which Chymists are wont to observe upon the pouring of Acid Spirits upon the Red Solution of Sulphur, dissolv’d in an Infusion of Pot-ashes, or in some other sharp Lixivium, the Praecipitated Sulphur before it subsides, immediately turning the Red Liquor into a White one.  And other Examples might be added of this way of producing Whiteness in Bodyes by Praecipitating them out of the Liquors wherein they have been Dissolv’d; but I think it may be more usefull to admonish you, Pyrophilus, that this observation admits of Restrictions, and is not so Universal, as by this time perhaps you have begun to think it; For though most Praecipitated Bodyes are White, yet I know some that are not; For Gold Dissolv’d in Aqua Regis, whether you Praecipitate it with Oyl of Tartar, or with Spirit of Sal Armoniack, will not afford a White but a Yellow Calx. Mercury also though reduc’d into Sublimate, and Praecipitated with Liquors abounding with Volatile Salts, as the Spirits drawn from Urine, Harts-horn, and other Animal substances, yet will afford, as we Noted in our first Experiment about Whiteness and Blackness, a White Praecipitate, yet with some Solutions hereafter to be mentioned, it will let fall an Orange-Tawny Powder.  And so will Crude Antimony, if, being dissolv’d in a strong Lye, you pour (as farr as I remember) any Acid Liquor upon the Solution newly Filtrated, whilst it is yet Warm.  And if upon the Filtrated Solution of Vitriol, you pour a Solution of one of these fix’d Salts, there will subside a Copious substance, very farr from having any Whiteness, which the Chymists are pleas’d to call, how properly I have elsewhere examin’d, the Sulphur of Vitriol.  So that most part of Dissolv’d Bodyes being by Praecipitation brought to White Powders, and yet some affording Praecipitates of other Colours, the reason of both the Phaenomena may deserve to be enquir’d into.

EXPERIMENT XIII.

Some Learned Modern Writers[15] are of Opinion, that the Account upon which Whiteness and Blackness ought to be call’d, as they commonly are, the two Extreme Colours, is, That Blackness (by which I presume is meant the Bodyes endow’d with it) receives no other Colours; but Whiteness very easily receives them all; whence some of them compare Whiteness to the Aristotelian Materia prima, that being capable of any sort of Forms, as they suppose White Bodyes to be of every kind of Colour.  But not to Dispute about Names or Expressions, the thing it self that is affirm’d as Matter of Fact, seems to be True enough in most Cases, not in all, or so, as to hold Universally.  For though it be a common