as to investigate the Mechanical Causes of Precipitation OF THE MECHANICAL CAUSES OF CHYMICAL PRECIPITATION CHAP. I. BY Precipitation is here meant such an agitation or motion of a heterogeneous liquor as in no long time makes the parts of it subside and that usually in the form of a powder or other consistent body As on many occasions Chymists call the substance that is made to fall to the bottom of the liquor the Precipitate so for brevity sake we shall call the body that is put into the liquor to procure that subsiding the Precipitant as also that which is to be struck down the Precipitable substance or matter and the liquor wherein it swims before the separation the Menstruum or Solvent When a hasty fall of a heterogeneous body is procured by a Precipitant the Operation is called Precipitation in the proper or strict sense But when the separation is made without any such addition or the substance separated from the fluid part of the liquor instead of subsiding emerges then the word is used in a more comprehensive but less proper acceptation As for the Causes of Precipitation the very name it self in its Chymical sense having been scarce heard of in the Peripatetic Schools it is not to be expected that they should have given an account of the Reasons of the thing And 't is like that those few Aristotelians that have by their converse with the laboratories or writings of Chymists taken notice of this Operation would according to their custom on such occasions have recourse for the explication of it to some secret sympathy or antipathy between the bodies whose action and reaction intervenes in this Operation But if this be the way proposed of accounting for it I shall quickly have occasion to say somewhat to it in considering the ways proposed by the Chymists who were wont to refer Precipitation either as is most usual to a sympathy betwixt the Precipitating body and the Menstruum which makes the Solvent run to the embraces of the Precipitant and so let fall the particles of the body sustained before or with others to a great antipathy or contrariety between the acid salt of the Menstruum and the fixed salt of the Oil or solution of calcined Tartar which is the most general and usual Precipitant they imploy But I see not how either of these causes will either reach to all the Phaenomena that have been exhibited or give a true account even of some of those to which it seems applicable For first in Precipitations wherein what they call a sympathy between the liquors is supposed to produce the effect this admired sympathy does not in my apprehension evince such a mysterious occult Quality as is presumed but rather consists in a greater congruity as to bigness shape motion and pores of the minute parts between the Menstruum and the Precipitant than between the same Solvent and the body it kept before dissolved And though this sympathy rightly explained may be allowed to have an interest in some such Precipitations as let fall the dissolved body in its pristine nature and form and only reduced into minute powder yet I find not that in the generality of Precipitations this Doctrine will hold For in some that we have made of Gold and Silver in proper Menstruums after the subsiding matter had been well washed and dried several Precipitates of Gold made some with oil of Tartar which abounds with a fixed salt and is the usual Precipitant and some with an Urinous Spirit which works by Vertue of a salt highly fugitive or Volatile I found the powder to exceed the weight of the Gold and Silver I had put to dissolve and the Eye it self sufficiently discovers such Precipitates not to be meer metalline powders but Compositions whose consisting not as hath been by some body suspected of the combined Salts alone but of the metalline parts also may be strongly concluded not only from the ponderousness of divers of them in reference to their bulk but also manifestly from the reduction of true malleable metals from several of them CHAP. II. THE other Chymical way of explicating Precipitations may in a right sence be made use of by a Naturalist on some particular occasions But I think it much too narrow and defective as 't is in a general way proposed to be fit to be acquiesced in For first 't is plain that 't is not only Salt of Tartar and other fixed Alcalies that precipitate most bodies that are dissolved in acid Menstruums as in making of Aurum fulminans oil of Tartar precipitates the Gold out of Aqua Regis But acid liquors themselves do on many occasions no less powerfully precipitate metals and other bodies out of one another Thus spirit of Salt as I have often tried precipitates Silver out of Aqua fortis The corrosive Spirit of Nitre copiously precipitates that white powder whereof they make Bezoardicum Minerale Spirit or oil of Sulphur made by a glass-bell precipitates Corals Pearls c. dissolved in Spirit of Vinegar as is known to many Chymists who now use this Oleum Sulphuris per Campanam to make the Magistery of Pearls c. for which vulgar Chymists imploy Oleum Tartari per deliquium I have sometimes made a Menstruum wherein though there were both Acid and Alcalizate Salts yet I did not find that either acid Spirits or oil of Tartar or even Spirit of Urine would precipitate the dissolved substances And I have observed both that Salts of a contrary nature will precipitate bodies out of the same Menstruum as not only Salt of Tartar but Sea-salt being dissolved will precipitate each other and each of them apart will precipitate Silver out of Aqua fortis and that even where there is a confessed contrariety betwixt two liquors it may be so ordered that neither of them shall precipitate what is dissolved by the other of which I shall have occasion to give ere long a remarkable instance But it will best appear that the abovementioned Theories of the Peripateticks and Chymists are at least insufficient to solve the Phaenomena many of which were probably not known to most of them and perhaps not weigh'd by any if we proceed to observe the Mechanical ways by which Precipitations may be accounted for whereof I shall at present propose some Number and say somewhat of each of them apart not that I think all of them to be equally important and comprehensive or that I absolutely deny that any one of them may be reduced to some of the other but that I think it may better elucidate the subject to treat of them severally when I shall have premised that I would not thence infer that though for the most part Nature does principally effect Precipitations by one or other of these ways yet in divers cases she may not imploy two or more of them about performing the operation To precipitate the Corpuscles of a metal out of a Menstruum wherein being once throughly dissolved
if it be well ground with near an equal weight of Quicksilver and be a few times sublimed to mix them the more exactly it will become so mild that 't will not so much as taste sharp upon the tongue so that Chymists are wont to call it Mercurius dulcis And yet this Dulcification seems to be performed in a Mechanical way For most part of the Salts that made the Sublimate so Corrosive abide in the Mercurius dulcis but by being compounded with more Quicksilver they are diluted by it and which is more considerable acquire a new Texture which renders them unfit to operate as they did before when the fretting Salts were not joyn'd with a sufficient quantity of the Mercury to inhibit their corrosive activity It may perhaps somewhat help us to conceive how this change may be made if we imagine that a company of meer Knife-blades be first fitted with Hafts which will in some regard lessen their wounding power by covering or casing them at that end which is design'd for the handle though their insertion into those Hafts turning them into Knives makes them otherwise the fitter to cut and pierce and that each of them be afterwards sheathed which is as it were a hafting of the Blades too for then they become unfit to cut or stab as before though the Blades be not destroyed Or else we may conceive these Blades without Hafts or Sheaths to be tied up in bundles or as it were in little faggots with pieces of wood somewhat longer than themselves opportunely placed between them For neither in this new Constitution would they be fit to cut and stab as before And by conceiving the edges of more or fewer of the Blades to be turn'd inwards and those that are not to have more or less of their points and edges to be sheath'd or otherwise cover'd by interpos'd bodies one may be help'd to imagine how the genuine effects of the Blades may be variously lessen'd or diversifi'd But whether these or any other like changes of Disposition be fancy'd it may by Mechanical Illustrations become intelligible how the Corrosive Salts of common Sublimate may lose their efficacy when they are united with a sufficient quantity of Quicksilver in Mercurius dulcis In which new state the Salts may indeed in a Chymical phrase be said to be satiated but this Chymical phrase does not explicate how this Saturation takes away the Corrosiveness from Salts that are still actually present in the sweet Mercury And by Analogy to some such Explications as the above propos'd a possible Account may be render'd why fretting Salts do either quite lose their sharpness as Alkalies whilst they are imbodied with Sand in common Glass or lose much of their Corrosive Acidity as Oyl of Vitriol does when with Steel it composes Vitriolum Martis or else are transmuted or disguis'd by conjunction with some corroded bodies of a peculiar Texture as when Aqua Fortis does with Silver make an extreamly bitter Salt or Vitriol and with Lead one that is positively sweet almost like common Saccharum Saturni EXPER. XX. TO shew how much the Efficacy of a Menstruum may depend even upon such seemingly slight Mechanical Circumstances as one would not easily suspect any necessity of I shall employ an Experiment which though the unpractis'd may easily fail of making well yet when I tried it after the best manner I did it with good success I put then upon Lead a good quantity of well rectified Aqua Fortis in which the Metal as I expected continued undissolved though if the Chymists say truly that the dissolving power of the Menstruum consists onely in the acid Salts that it abounds with it seems naturally to follow that the more abundance of them there is in a determinate quantity of the Liquor it should be the more powerfully able to dissolve Metalline and Mineral bodies And in effect we see that if Corrosive Menstruums be not sufficiently dephlegmed they will not work on divers of them But notwithstanding this plausible Doctrine of the Chymists conjecturing that the Saline Particles that swam in our Aqua Fortis might be more throng'd together than was convenient for a body of such a Texture of Saline parts and such intervals between them I diluted the Menstruum by adding to it what I thought fit of fair water and then found that the desired Congruity betwixt the Agent and the Patient emerged and the Liquor quickly began to fall upon the Metal and dissolve it And if you would try an Experiment to the same purpose that needs much less circumspection to make it succeed you may instead of employing Lead reiterate what I elsewhere mention my self to have tried with Silver which would not dissolve in too strong Aqua fortis but would be readily fallen upon by that Liquor when I had weaken'd it with common water And this it may suffice to have said at present of the power or faculty that is found in some bodies of Corroding or Dissolving others Whereof I have not found among the Aristotelians I have met with so much as an Offer at an Intelligible account And I the less expect the vulgar Chymists will from their Hypostatical Principles afford us a Satisfactory one when besides the Particulars that from the nature of the things and Helmont's Writings have been lately alledg'd against their Hypothesis I consider how slight accounts they are wont to give us even of the familiar Phaenomena of Corrosive Liquors For if for example you ask a vulgar Chymist why Aqua fortis dissolves Silver and Copper 't is great odds but he will tell you 't is because of the abundance of fretting Salt that is in it and has a cognation with the Salts of the Metal And if you ask him why Spirit of Salt dissolves Copper he will tell you 't is for the same reason and yet if you put Spirit of Salt though very strong to Aqua fortis this Liquor will not dissolve Silver because upon the mixture the Liquors acquire a new Gonstitution as to the Saline Particles by vertue of which the mixture will dissolve instead of Silver Gold Whence we may argue against the Chymists that the Inability of this compounded Liquor to work on Silver does not proceed from its being weaken'd by the Spirit of Salt as well because according to them Gold is far the more compact metal of the two and requires a more potent Menstruum to work upon it as because this same compounded Liquor will readily dissolve Copper And to the same purpose with this Experiment I should alledge divers others if I thought this the fittest place wherein I could propose them SECT II. About the Mechanicall Origine of CORROSIBILITY COrrosibility being the quality that answers Corrosiveness he that has taken notice of the Advertisement I formerly gave about my use of the Term Corrosiveness in these Notes may easily judge in what sense I employ the name of the other Quality which whether you will stile it
Electric as soon as we could to settle notwithstanding its hanging freely at the bottom of the string This course of rubbing on the edge of the Amber we pitch'd upon for more than one reason for if we had chafed the flat side the Amber could not have approached the body it had been rub'd on without making a change of place in the whole Electric and which is worse without making it move contrary to the nature of heavy bodies somewhat upwards whereas the Amber having by reason of its suspension its parts counterpoised by one another to make the excited edge approach to another body that edge needed not at all ascend but onely be moved horizontally to which way of moving the gravity of the Electric which the string kept from moving downwards could be but little or no hinderance And agreeably to this we found that if as soon as the suspended and well rubb'd Electric was brought to settle freely we applied to the chafed edge but without touching it the lately mention'd Cushion which by reason of its rough Superficies and porosity was fit for the Electrical Effluvia to fasten upon the edge would manifestly be drawn aside by the Cushion steadily held and if this were slowly removed would follow it a good way and when this body no longer detain'd it would return to the posture wherein it had settled before And this power of approaching the Cushion by vertue of the operation of its own steams was so durable in our vigorous piece of Amber that by once chafing it I was able to make it follow the Cushion no less than ten or eleven times Whether from such Experiments one may argue that 't is but as 't were by accident that Amber attracts another body and not this the Amber and whether these ought to make us question if Electricks may with so much propriety as has been hitherto generally supposed be said to Attract are doubts that my Design does not here oblige me to examine Some other Phaenomena might be added of the same Tendency with those already mention'd as the advantage that Electrical Bodies usually get by having well polish'd or at least smooth Surfaces but the Title of this Paper promising some Experiments about the Production of Electricity I must not omit to recite how I have been sometimes able to produce or destroy this Quality in certain bodies by means of alterations that appear'd not to be other than Mechanical EXPER. I. ANd first having with a very mild heat slowly evaporated about a fourth part of good Turpentine I found that the remaining body would not when cold continue a Liquor but harden'd into a transparent Gum almost like Amber which as I look'd for proved Electrical EXPER. II. SEcondly by mixing two such liquid Bodies as Petroleum and strong Spirit of Nitre in a certain proportion and then distilling them till there remained a dry mass I obtain'd a brittle substance as black as Jet and whose Superficies where it was contiguous to the Retort was glossie like that Mineral when polished and as I expected I found it also to resemble Jet in being endowed with an Electrical Faculty EXPER. III. THirdly Having burnt Antimony to ashes and of those ashes without any addition made a transparent Glass I found that when rubb'd as Electrical Bodies ought to be to excite them it answer'd my expectation by manifesting a not inconsiderable Electricity And this is the worthier of notice because that as a Vitrum Antimonii that is said to be purer than ordinary may be made of the Regulus of the same Mineral in whose preparation you know a great part of the Antimonial Sulphur is separated and left among the Scoriae so Glass of Antimony made without additament may easily as experience has inform'd us be in part reduc'd to a Regulus a Body not reckon'd amongst Electrical ones And that you may not think that 't is onely some peculiar and fixt part of the Antimony that is capable of Vitrification let me assure you that even with the other part that is wont to flye away namely the Flowers an Antimonial Glass may without an addition of other Ingredients be made EXPER. IV. FOurthly The mention of a Vitrified Body brings into my mind that I more than once made some Glass of Lead per se which I found no very easie work that also was not wholly destitute of an Electrical Vertue though it had but a very languid one And it is not here to be overlook'd that this Glass might easily be brought to afford again malleable Lead which was never reckon'd that I know of among Electrical Bodies EXPER. V. FIfthly Having taken some Amber and warily distill'd it not with Sand or powder'd Brick or some such additament as Chymists are wont to use for fear it should boyl over or break their Vessels but by its self that I might have an unmixed Caput mortuum Having made this Distillation I say and continued it till it had afforded a good proportion of phlegm Spirit Volatile Salt and Oyl the Retort was warily broken and the remaining matter was taken out in a lump which though it had quite lost its colour being burnt quite black and though it were grown strangely brittle in comparison of Amber so that they who believe the vertue of attracting light Bodies to flow from the substantial form of Amber would not expect it in a Body so changed and deprived of its noblest parts Yet this Caput mortuum was so far from having lost its Electrical Faculty that it seemed to attract more vigorously than Amber it self is wont to do before it be committed to Distillation And from the foregoing Instances afforded us by the Glass of Antimony we may learn that when the form of a Body seems to be destroyed by a fiery Analysis that dissipates the parts of it the remaining substance may yet be endowed with Electricity as the Caput mortuum of Amber â—ay acquire it as in the case of the Glass of Antimony made of the Calx and of the Flowers And from the second Example above-mentioned and from common Glass which is Electrical we may also learn that Bodies that are neither of them apart observed to be endowed with Electricity may have that Vertue result in the compounded substance that they constitute though it be but a factitious Body To the foregoing Experiments whose Success is wont to be uniform enough I shall adde the Recital of a surprising Phaenomenon which though not constant may help to make it probable that Electrical Attractions need not be suppos'd still to proceed from the substantial or even from the essential Form of the Attrahent but may be the effects of unheeded and as it were fortuitous Causes And however I dare not suppress so strange an Observation and therefore shall relate that which I had the luck to make of an odd sort of Electrical Attraction as it seem'd not taken notice of that I know of by any either Naturalist or other Writer and