then, whereas it has been already ſaid, that the Cæruleous Colour was by Acid Salts aboliſhed, this Yellowiſh one ſurviv'd without any conſiderable Alteration, ſo that unleſs our Author's Words be taken in a very Limited Senſe, we muſt conclude, that either his Memory mis-inform'd him, or that his White Nephritick Wood, and the Sadder Colour'd one which we employ'd, were not altogether of the ſame Nature: What he mentions of the Cup made of Lignum Nephriticum, we have not had Opportunity to try, not having been able to procure pieces of that Wood great enough, and otherwiſe fit to be turned into Cups; but as for what he ſays in the Title of his Experiment, that this Wood tinges the Water with all Sorts of Colours, that is much more than any of thoſe pieces of Nephritick Wood that we have hitherto employ'd, was able to make good; The change of Colours diſcernable in a Vial full of Water, Impregnated by any of them, as it is directed towards a place more Lightſome or Obſcure, being far from affording a Variety anſwerable to ſo promiſing a Title. And as for what he tells us, that in the Dark the Infuſion of our Wood will reſume a Cæruleous Colour, I wiſh he had Inform'd us how he Try'd it.
But this brings into my mind, that having ſometimes for Curioſity ſake, brought a round Vial with a long Neck fill'd with the Tincture of Lignum Nephriticum into the Darken'd Room already often mention'd, and holding it ſometimes in, ſometimes near the Sun-beams that enter'd at the hole, and ſometimes partly in them, and partly out of them, the Glaſs being held in ſeveral poſtures, and look'd upon from ſeveral Neighbouring parts of the Room, diſclos'd a much greater Variety of Colours than in ordinary inlightn'd Rooms it is wont to do; exhibiting, beſides the uſual Colours, a Red in ſome parts, and a Green in others, beſides Intermediate Colours produc'd by the differing Degrees, and odd mixtures of Light and Shade.
By all this You may ſee, Pyrophilus, the reaſonableneſs of what we elſewhere had occaſion to mention, when we have divers times told you, that it is uſefull to have New Experiments try'd over again, though they were, at firſt, made by Knowing and Candid Men, ſuch Reiterations of Experiments commonly exhibiting ſome New Phænomena, detecting ſome Miſtake or hinting ſome Truth, in reference to them, that was not formerly taken notice of. And ſome of our friends have been pleas'd to
think, that we have made no unuſefull addition to this Experiment, by ſhewing a way, how in a moment our Liquor may be depriv'd of its Blewneſs, and reſtor'd to it again by the affuſion of a very few drops of Liquors, which have neither of them any Colour at all of their own. And that which deſerves ſome particular wonder, is, that the Cæruleous Tincture of our Wood is ſubject by the former Method to be Deſtroy'd or Reſtor'd, the Yellowiſh or Reddiſh Tincture continuing what it was. And that you may ſee, that Salts are of a conſiderable uſe in the ſtriking of Colours, let me add to the many Experiments which may be afforded us to this purpoſe by the Dyers Trade, this Obſervation; That as far as we have hitherto try'd, thoſe Liquors in general that are ſtrong of Acid Salts have the Power of Deſtroying the Blewneſs of the Infuſion of our Wood, and thoſe Liquors indiſcriminatly that abound with Sulphureous Salts, (under which I comprehend the Urinous and Volatile Salts of Animal Subſtances, and the Alcaliſate or fixed Salts that are made by Incineration) have the vertue of Reſtoring it.
A Corollary of the Tenth Experiment.
That this Experiment, Pyrophilus, may be as well Uſefull as Delightfull to You, I muſt mind You, Pyrophilus, that in the newly mention'd Obſervation, I have hinted to You a New and Eaſie way of Diſcovering in many Liquors (for I dare not ſay in all) whether it be an Acid or Sulphureous Salt, that is Predominant; and that ſuch a Diſcovery is oftentimes of great Difficulty, and may frequently be of great Uſe, he that is not a Stranger to the various Properties and Effects of Salts, and of how great moment it is to be able to diſtinguiſh their Tribes, may readily conceive. But to proceed to the way of trying other Liquors by an Infuſion of our Wood, take it briefly thus. Suppoſe I have a mind to try whether I conjecture aright, when I imagine that Allom, though it be plainly a Mixt Body, does abound rather with Acid than Sulphureous Salt. To ſatisfie my ſelf herein, I turn my back to the Light, and holding a ſmall Vial full of the Tincture of Lignum Nephriticum, which look'd upon in that Poſition, appears Cæruleous, I drop into it a little of a ſtrong Solution of Allom made in Fair Water, and finding upon the
Affuſion and ſhaking of this New liquor, that the Blewneſs formerly conſpicuous in our Tincture does preſently vaniſh, I am thereby incited to ſuppoſe, that the Salt Prædominant in Allom belongs to the Family of Sour Salts; but if on the other ſide I have a mind to examine whether or no I rightly conceive that Salt of Urine, or of Harts-horn is rather of a Saline Sulphureous (if I may ſo ſpeak) than of an Acid Nature, I drop a little of the Saline Spirit of either into the Nephritick Tincture, and finding that the Cæruleous Colour is rather thereby Deepned than Deſtroy'd, I collect that the Salts, which conſtitute theſe Spirits, are rather Sulphureous than Acid. And to ſatisfie my ſelf yet farther in this particular, I take a ſmall Vial of freſh Tincture, and placing both it and my ſelf in reference to the Light as formerly, I drop into the Infuſion juſt as much Diſtill'd Vinegar, or other Acid liquor as will ſerve to Deprive it of its Blewneſs (which a few drops, if the Sour Liquor be ſtrong, and the Vial ſmall will ſuffice to do) then without changing my Poſture, I drop and ſhake into the ſame Vial a ſmall proportion of Spirit of Hartſhorn or Urine, and finding that upon this affuſion, the Tincture immediately recovers its Cæruleous Colour, I am thereby confirm'd
firm'd in my former Opinion, of the Sulphureous Nature of theſe Salts. And ſo, whereas it is much doubted by Some Modern Chymiſts to what ſort of Salt, that which is Prædominant in Quick-lime belongs, we have been perſwaded to referr it rather to Lixiviate than Acid Salts, by having obſerv'd, that though an Evaporated Infuſion of it will ſcarce yield ſuch a Salt, as Aſhes and other Alcalizate Bodyes are wont to do, yet if we deprive our Nephritick Tincture of its Blewneſs by juſt ſo much Diſtill'd Vinegar as is requiſite to make that Colour Vaniſh, the Lixivium of Quick-lime will immediately upon its Affuſion recall the Baniſhed Colour; but not ſo Powerfully as either of the Sulphureous Liquors formerly mention'd. And therefore I allow my ſelf to gueſs at the Strength of the Liquors examin'd by this Experiment, by the Quantity of them which is ſufficient to Deſtroy or Reſtore the Cæruleous Colour of our Tincture. But whether concerning Liquors, wherein neither Acid nor Alcaliſate Salts are Eminently Prædominant, our Tincture will enable us to conjecture any thing more than that ſuch Salts are not Prædominant in them, I take not upon me to determine here, but leave to further Tryal; For I find not that Spirit of