Robert Boyle (1627-1691)

Tracts Written by the Honourable Robert Boyle, Containing New Experiments, Touching the Relation Between Flame and Air. And About Explosions ...

London, 1672 [from Henry Marshall Leicester and Herbert S. Klickstein, A Source Book in Chemistry 1400-1900 (New York: McGraw Hill, 1952)]

The First Title.

Of the Difficulty of Producing Flame without Aire.

Experiment I.

A Way of Kindling Brimstone in vacuo Boyliano Unsuccessfully Tried. We took a small earthen melting Pot, of an almost Cylindrical figure, and well glaz'd (when it was first bak'd) by the heat; and into this we put a small cylinder of Iron of about an inch in thickness, and half as much more in Diameter, made red hot in the fire; and having hastily pump'd out the Air, to prevent the breaking of the Glass; when this vessel seem'd to be well emptied, we let down, by a turning key, a piece of Paper, wherein was put a convenient quantity of flower of Brimstone, under which the iron had been carefully plac'd; so that, being let down, that vehement heat did, as we expected, presently destroy the contiguous paper; whence the included Sulphur fell immediately upon the iron, whose upper part was a little concave, that it might contain the flowers when melted. But all the heat of the iron, though it made the Paper and Sulphur smoke, would not actually kindle either of them that we could perceive.

Experiment II.

An Ineffectual Attempt to Kindle Sulphur in Our Vacuum Another Way

Another way I thought of to examine the inflammability of Sulphur without Air; which, though it may prove somewhat hazardous to put it in practice, I resolved to try, and did so after the following manner:

Into a glass-buble of a convenient size, and furnish'd with a neck fit for our purpose, we put a little flower of Brimstone (as likely to be more pure and inflammable than common Sulphur;) and having exhausted the Glass, and secured it against the return of the Air, we laid it upon burning coals, where it did not take fire, but rise all to the opposite part of the glass, in the form of a fine powder; and that part being turned downward and laid on coals, the Brimstone, without kindling, rose again in the form of an expanded substance, which (being removed from the fire) was, for the most part, transparent, not unlike a yellow varnish.

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Though these unsuccessful attempts to kindle Sulphur in our exhausted Receivers, were made more discouraging by some more, that were made another way; yet judging that last way to be rational enough, we persisted somewhat obstinately in our endeavours, and conjecturing that there might be some unperceived difference between Minerals, that do all of them pass, and are sold for common Sulphur, I made trial, according to the way hereafter to be mentioned, with another parcel of brimstone, which differ'd not so much from the former, as to make it worth while to set down a description o it, that probably would not be useful.

But in this place, it may suffice to have given a general intimation of the possibility of the thing. The proof of it you will meet with under the third Title, when I come to tell you what use I endeavour'd to make of our sulphureous Flames.

Experiment III.

Shewing the Efficacy of Air in the Production of Flame, without Any Actually Flaming or Burning Body.

Having hitherto examin'd by the presence of the Air, what interest it has in kindling of Flame; it will not be impertinent to add an Experiment or two, that we tried to shew the same interest of the Air by the effects of its admission into our Vacuum. For I thought, it might reasonably be supposed that if such dispositions were introduc'd into a body, as that there should not appear any thing wanting to turn it into Flame but the presence of the Air, an actual ascension of that body might be produced by the admitted Air, without the intervention of any actual Flame, or Fire, or even heated substance; the warrentableness of which supposition may be judged by the two following Experiments.

When we had made the Experiment, ere long to be related in its due place, (viz. Title II. Exper. the 2nd) to examine the presumption we had, that even when the Iron was not hot enough to keep the melted Brimstone in such a heat, as was requisite to make it burn without Air, or with very little, it would yet be hot enough to kindle the Sulphur, if the Air had access to it: to examine this (I say) we made two or three several Tryals, and found by them, that if some little while after the flame was extinguished, the Receiver were removed, the sulphur would Presently take fire again, and flame as vigorously as before. But I thought it might without absurdity be doubted, whether or no the agency of the Air in the production of the flame might not be somewhat less than these trials would perswade; because that, by taking off the Receiver, the Sulphur was not only exposed to fresh Air, but also advantaged with a free scope for the avolution of those fumes, which in a close Vessel might be presum'd to have been unfriendly to the Flame.

How far this doubt may, and how far it should, be admitted, we may be assisted to discern by the subjoined experiment, though made in great part for another purpose; which you will perceive by the beginning of the Memorial I made of it, that runs thus;

Experiment IV.

A Differing Experiment to the Same Purpose with the Former.

Having a mind to try, at how great a degree of rarefaction of the Air it was possible to make Sulphur lame by the assistance of an adventitious heat, we caused such an experiment as the above mention'd to be reiterated, and the pumping to be continued for some time after the flame of the melted flowers of Brimstone appeared to be quite extinguished, and the Receiver was judged by those that managed the Pump (and that upon probable signs) to be very well exhausted. Then, without stirring the Receiver, we let in at the stop-cock very warily a little Air, upon which we could perceive, though not a constant flame, yet divers little flashes, as it were, which disclosed themselves by their bleu [sic] colour to be sulphureous flames; and yet the Air, that had suffic'd to re-kindle the Sulphur, was so little, that two exsuctions more drew it out again, and quite depriv'd us of the mentioned flashes. And when a little Air was cautiously let in again at the stop-cock, the like flashes began again to appear, which, upon two exeuctions [sic] more did again quite vanish, though, upon the letting in a little fresh Air the third time, they did once more reappear.

Whether and how far such experiments as these may conduce to explicate what is related of Fires suddenly appearing in long undisclosed Vaults or Caves to those that first broke into them, I may perchance elsewhere consider; but shall not here, enquire, especially being not fully satisfied of the truth of the matter of fact. ...

The Second Title.

Of the Difficulty of Preserving Flame without Air

Since it is generally, and in most cases justly, esteemed to be more easie to preserve Flame in a body that is already actually kindled, than to produce it there at first; we thought fit to try, whether at least bodies already burning might not be kept in that state without the concurrence of Air. And though in some of our formerly published Physico-mechanical experiments it happen'd that actually Flame would scarce last a minute or two in our large Pneumatical Receiver; yet because it seem'd not improbable, that mineral bodies once kindled might afford a vigorous and very durable flame; we thought fit to devise and make the following tryals: Whence probably we might receive some new information about the Diversities, and some other Phenomena of Flame, and the various degrees, wherein the Air is necessary or helpful to them.

Experiment I.

Reciting an Attempt to Preserve the Flame of Brimstone without Air

We put upon a thick metalline place a convenient quantity of flowers of Sulphur; and having kindled them in the Air, we nimbly conveyed them into a Receiver, and made haste to pump out some of the included Air, partly for other reasons, and partly that the cavity of the Receiver might be the sooner freed from smok [sic], which would, if plentiful, both injure the flame, and hinder our sight. As soon as the Pump began to be plied, or to be lessen'd at every exsuction of the Air; and in effect, it expir'd before the Air was quite drawn out. Nor did it, upon the early removal of the Receiver, do any more than afford, for a very little while, somewhat more of the smoak in the open Air, than it appear'd to do before.

The reiteration of this experiment presently after, afforded us nothing new, worth mentioning in this place.

Experiment II.

Relating a Tryal about the Duration of the Flame of Sulphur in vacuo Boyliano.

To vary a little the foregoing Experiment, and try to save some moments of time, which on these occasions is to be husbanded with the utmost care; having provided a Cylinder of ion larger than the former, that it might be its bulk, being once heated, both contribute to the asccension [sic] of the Sulphur, and to the lasting of its flame, we made a tryal, that I find registred to this effect:

We took a pretty big lump of Brimstone, and tied it to the turning-key; and having got what else was necessary in a readiness, we caus'd the iron-plate to be hastily brought red-hot from the fire, and put upon a Pedestal, that the flame might be the more conspicuous; and, having nimbly cemented on the Receiver, we speedily let down the suspended Brimstone, till it rested upon the red-hot iron, by which being kindled, it sent up a Pump, till we had, as we conjectur'd, emptied the Receiver; which we could not do without withdrawing together with the Air much sulphureous smok, (that was offensive enough both to the eyes and nostrils.) But notwithstanding this pumping out of the Air, though the flame did seem gradually to be somewhat impaired; yet it manifestly continued burning much longer, than by the short duration of other flames in out Receivers (when diligence is us'd to withdraw the air from them) one could have expected. And especially one time, (for the experiment was made more than once) the flame lasted, till the Receiver was judg'd to be well exhausted; and some thought it did so survive the exhaustion, that it went not out so much for want of Air, as Fuel; the Brimstone appearing when we took off the Receiver, either to have been consum'd by the fire that fed on it, or to have casually run off from the Iron, whose heat had kept it constantly melted.

In case you should have a mind to prosecute Experiments of the nature of this and the precedent, it may not prove useless, if I intimate to you the following Advertisements.

1. For the red-hot iron above mentioned, we thought it not amiss to provide, instead of the melting-pot imploy'd in the first experiment, a Pedestal (if I may so call it) made of a lump of dryed Tobacco-pipe-clay, that the vehement heat of the iron might neither fill the Receiver with the smok of what it lean'd on, nor injure the engine, if it should rest immediately upon that; And this Pedestal should be so plac'd, that the iron may be as far, as you can, from the sides of the Receiver, which else the excessive heat would endanger.

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