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On the influence of the air in determining the crystallization of saline solutions
OIL [hc I,bJl~~cc
J58
id I/lc :lir itr Ct*ysCdli=Uiion.
(2) ~1105~ radius is ol’ the Sam length as that of one of the IIIOVCis attached to the platform, and nmy slide along its edge able ph~cs, ]~orieontdly, so RY in every situulioil to adjust 1t9 cfntr; precisely to the pivot of Lhe lower hillgC of that plaue to WhlCll lt 1s applied. Tllc pivot of the middle hinge will then correspond to some point on the cm, nrd if the latter be divided into dcgrces and parts, the requisite data are immcdiatcly obtained, and the calculation is lyade with the utmost facility, by means of a table of tanwnts. Or a tangent rod T, as represented in the figure, may be a (fde4 having, on one side, lines drawn through the several divisions of the rluadrant as far as convenient, and on the other, a scale of crlual parts. The force P, then, is to one of the forces, K, as twice th tangent of the angle of elevation is to radius. The machine which I have employed for this purpose, and which is rcprescnted in the figure, is about four feet in length by three feet and a half high; the movcable planes are about 10; inches in length, by 1: in breadth, and the sliding plants 1 S iilclles in hgth by
2:
in
width.
The earliest account which I have seen of any mechanical implcmxlt constructed on the principle prcscnteil by this apparatus, is one contained in an old work by Ven Mandy, published near the beginning of tlic last century, where it is called aI1 “ augnicnting pnwcr or force,” and is mcrcly dcscribcd, without a11 invcsti+ion of its principle of action. It is there prescnteJ as a 1Tcvicc alluptctl by a baker to facilitate the process of kneatlin r his dough. It has been applied to a variety of USCaul purposes, such as of late years tlic construction of oil and printing presses, the cuttug and perforating of mctnls, and other operations in which intense action through n very limited space is required to be produced by mcnns of a small lnovin= force. u#I ereI1 t names have been l~roposcd for this kind of mechanical ~OWW, but IIOIIC has yet obtnioctl, I bclicvc, a gcncrsl adoption. The term 6‘lo@ join/, ” is ncithcr good Knglish, nor in auy way appropriate lo the subject. The name of “ prgreasivc IevcP has StnlletilllCS bccll applieli to it; but from what has ~JrCC~lh~, it will be SW11 that it llils nothing ill commim with the ordiu:iry lever, and thou4 the latter may somctimcs bc cmploycil ns the metliunl through Whlc .‘I 1 lh moving force is appliell, yet it constitutes no csscntlal part or lllc machinr, any more than if applied to tlic rnidd]r “f a cord to iIlCIW%e the tCllsil~l1 ill the ITl]JC ?rluuhke. II1 rCfCrCnCe to tllc mode of uniting lh ~~latlcs by hixp, OKother equivalent means, I have proposed the term cortfitiril~ power, ntd to the lla&ulsr a~pnrAus above described, have1given the name of fric&o. 011 the ktflrience Of llre Air in determining tlic C~y.nt(&&ioj, of Saline Solutions. BIJ 'lhow.~s Gnnn~~,Es~. A. M. F. 12. s. ~..r ‘Tn_Ephenomenon rcfcrrcd to has long been known, and popularly enlnbWl in tlte cast of Glaubcr’s salt, without auy adcquatc es_
planation. A phial, or flask, is filled with a boiling AirtHtd y&; tion of sulphate of soda or Glauher’s salt, and its mouth immerKtfe$ stopped by a cork, or a piece of bladder is tied tightly over it, iphj < still hot. The solution, thus protected from the atmosphere, &e& rally cools without cr)stallizing, although it contains a great exeeae of salt, and continues Entirely liquid for hours, and even days. B& upon withdrawin g the stopper, or puncturing the bladder, and at& mitting air to the solution, it is immediately resolved into a spongy crystalline mass, with the evolution of much heat. The crystallization was attributed to the pressure of the atmosphere suddenly n& mitted, till it was shown that the same phenomenon occurred, whew air was admitted to a solution already subject to the atmospheric pressure. Recourse was likewise had to the supposed agency of solid particles floatin,.m in the air, and brought by means of it into contact with the solution; or it was supposed that the contact of gaseous molecules thcmselvrs might determine crystallization, as well as solid particles. But although the phenomenon has been the subject of much speculation among chemists, it is generally allowed that no satisfactory csplanation of it has yet been proposed. In experimenting upon this subject, it was found that hot concentrated solutions, in phials, or other receivers, might beinverted over mercury in the pneumatic trough, and still remain liquid on cooling; and thus the causes which determine crystallizatiou, were more readily examined. For this purpose, it was absolutely necessary that the mercury in the trough should be previously heated to llO” or 120’; for otherwise, that part of the solution in contact with the mercury cooled so rapidly, as to determine crystallization in .Phe lower part of the receiver, Ion* before the upper part had fallen30 In such cases, crystallization the temperature of the atmosp Piere. be inning on the surface of the mercury, advanced slowly and reAbove, there always remained a rgufarlp through the solution. tion o ’the solution too weak to crystallize, being impoveri$e (p”by It was also necessary to. the dense formation of crystals below. clean the lower and external part of the receivers, ,when’ .pl&e&%r the trough, from any adhering solution,, as a communicatioti sf @a& line matter was sometimes formed between the solution -in thb’F& When these precautions”“were ceiver and the atmosphere without. attended to, saline solutions over mercury remained as long wifho‘ut crystallizing, as when separated from the atmosphere in the usual mode. Solutions which completely filled the receivers when placed in the trough, allowed a portion of mercury to enter, by contracting materially as they cooled. A bubble of air could thus be thrown u without expelling any of the solution from the receiver, and t Re crystallizatron determined, without exposing the solution directly to the atmosphere. The first observation made, was, that solutions of sulphate of sodo sometimes did not crystallize at all upon the introduction of a hubThis irregularity was ble of air, or at least for a considerable time. chiefly observed in solutions formed at tcmperaturcs not exceedrng
360
Ofa the InJEuelzce of the Air in CrJjsluEEization.
1500 or ITO”, although water dissolves more of the sulphate of soda at, these inferior temperatures, than at a boiling heat. Brisk ebulli_ tion for a few seconds, however, rendered the solution upon cooling amendable to the usual influence of the air. In all successful cases, crystallization commenced in the upper part of. the receiver around the bubble of air, but pervaded the whole soj’utlon In a very few se_ A light glass bead was thrown up into a solution without conds. disturbing it. It occurred to me, that, since the effect of air could not he ac_ counted for on mechanical principles, it might arise from a certain Water always holds in solution cl~emical action upon the solution. a certain portion of air at the temperature of the atmosphere, which Cooled in a close vessel after boilivg, it parts with upon boiling. and then exposed to the atmosphere, it re-absorbs its usual proportion Now, this absorbed air ap ears to affect of air with great avidity. in a minute degree, the power of water to dissolve otfler bodies; at least, a considerable part of it is extricated upon the solution of salts. When a bubble of air is thrown up into a soluqion of sulpbate of soda, which has previously been ‘boded and deprived of all its air, a small quantity of air will certainly-be absorbed by the solution around the bubble. A slight reduction in the solvent power of the menstruum, will ensue at the spot where the air is dissolved. But the menstruum is greatly overloaded with saline matter, and ready to deposit it; the shghtest diminution of its solvent. power may, therefore, decide the precipitation or crystallization of the unnatural exThe absorption of air may, in this way, cess of saline matter. commence and determine the precipitation of the excess of sulphate of soda in solution. Here, too, we have an explanation of the fact just mentioned, that solutions of sulphate of soda which have not been boiled, are less affected b exposure to the air than well boiled solutions; for the former stk*71 retain the most of their air, and do not absorb air SO eagerly on exposure, as solutions which have been boiled. But the theory was most powerfully confirmed by an experimental examination of tbc influence of other gases, besides atmospheric air, Z?%eij*injluence was found to be prein determining crystallization. cisely p~oportmzate to the degree in whicl~ they are ahorBed OTdissolved by water cm1 the dine solutions. To a solution of sulphate of soda over mercury, which Ilad not been affected by a bubble of atmospheric air, a bubble of carbonic acid gas was added. Crystallization was instantly determined around the bubble, and thence through the whole mass. Water is capable of dissolving its own volume of carbonic acid gas, and a solution of sulphate of soda as strong as could be employed, was found by Saussure to absorb more than half its volume. In a solution of sulphate of soda, which was rather weak, both common air and carbonic acid gas failed to destroy the equilibrium; but a small bubble of ammoniacal gas instantly.determined crystallization. When gases arc employed which water dissolves abundantly, such
On some new mocks of Forming
f’y@$,i$,$~
381
3s ammoniacal and. sulphurous acid gases, the c~y.eial~iz$tiun procc& most vigorously. It is not deferred till..tjle bubble.6$$aa reaches the top of t$ receiver, as always happens with common.a!r, and frequently with carbo!ic acid gas; but the .tfack of the bubble bec_onlcs the common axis of innumerable crystalline planes, upon which It appears to be .borne upwards; and sometimes before the ascent is completed, the bubble is entangled and arrested by crystalline arrangements which precede it. Tllc number of gases which are less soluble in water !had atmodpheric air, is not considerable; but of these, hydrogen r was found to be decidedly least influential in determininlr cryeta Ilzatlon. Minute quantities of foreign liquids, soluble in water, likewise disposed the saline solution to irnmcdiate crystallization, M. might It is known be expected, and none with greater et&t than alcohol. that alcohol can precipitate sulphatc of soda from its nqueous solutions. The soluble gases I suppose to possess a similnr property. These facts appear to warrant the conclusion, that air tlctermiqes the crystallization of supersaturated saline solutions, by dissolving in the water, and thereby giving a shock to the feeble power by which the excess of salt is held in solution. ‘** Since the foregoing observations were printed, the author has percciyed that M. Gay-Lussnc! in his paper on crystallizatipn, (&L de Cl&z. tom. lxrxvil.) had distinctly thrown out the same theory as a conjecture, although the circumstance is nnt noticed by any But as M. Gag-Lusksc briu- forward systcmatlc chemical_wrlter. no esperimcntal illustration of the theory, and, indeed, a&luces’one esprriment as unfavourablc to it, the esperimental contirmdtiorj’of [Phil. ~fug. the theory is novel, and was certainly required.
Oa some nets mdes 0J formif&
Pyroplrorrrs.
By
M_.(#AT-Lussati . :-*.
M. tiAv-Lussrc,,in forming this substance, ubed.~i~lc~djSi~, black instead of liooey,or ROW, osually employed.’ ‘$:PotlishSlu& hunted with this form nf cnrbon, gave at first carbonic@id:sn phurous has, and nearly. in equal volumes; was obtalned nearly pure, and at last it was mixed withOosidd:of carbon, and this eventually prevailed. .‘rhe pytophorus B$ormed, burnt readily. M. tiay-Lussac is of ppinion, that carbon IS not necessary tv the combustion: he made a mixture of nearly 75 parts of alum, and 5.~5 of lamp-black, or 1 atom of the former and 5.5 atoms of the latter; and this mixture, when cslcined, at nearly a white heat, gave a reddish-brown product, contiiillillg, no traces of carbon, but it burnt very rfadily, and left ngrayiAwhttc Sulphate of is not cssentinl tci the preparation.
residuum.
Alum
riragnesia producc~ the same effect; sulphurct of l)otasGurn alone does nnt, hnwever, inllame spoofaneously in mass; and it occurred to M. Gil!-LUSsaC, that alumina, or magnesia, acted nw.rcl~ by llividing the s\\IllIlllret; that this WRS the C;ISC, was l~rovcd by sul>~~ltufin~ c\rarcorrl few them, 41; Vol.. ITI.--No. 5.-hlns, 1SZ).
J58
id I/lc :lir itr Ct*ysCdli=Uiion.
(2) ~1105~ radius is ol’ the Sam length as that of one of the IIIOVCis attached to the platform, and nmy slide along its edge able ph~cs, ]~orieontdly, so RY in every situulioil to adjust 1t9 cfntr; precisely to the pivot of Lhe lower hillgC of that plaue to WhlCll lt 1s applied. Tllc pivot of the middle hinge will then correspond to some point on the cm, nrd if the latter be divided into dcgrces and parts, the requisite data are immcdiatcly obtained, and the calculation is lyade with the utmost facility, by means of a table of tanwnts. Or a tangent rod T, as represented in the figure, may be a (fde4 having, on one side, lines drawn through the several divisions of the rluadrant as far as convenient, and on the other, a scale of crlual parts. The force P, then, is to one of the forces, K, as twice th tangent of the angle of elevation is to radius. The machine which I have employed for this purpose, and which is rcprescnted in the figure, is about four feet in length by three feet and a half high; the movcable planes are about 10; inches in length, by 1: in breadth, and the sliding plants 1 S iilclles in hgth by
2:
in
width.
The earliest account which I have seen of any mechanical implcmxlt constructed on the principle prcscnteil by this apparatus, is one contained in an old work by Ven Mandy, published near the beginning of tlic last century, where it is called aI1 “ augnicnting pnwcr or force,” and is mcrcly dcscribcd, without a11 invcsti+ion of its principle of action. It is there prescnteJ as a 1Tcvicc alluptctl by a baker to facilitate the process of kneatlin r his dough. It has been applied to a variety of USCaul purposes, such as of late years tlic construction of oil and printing presses, the cuttug and perforating of mctnls, and other operations in which intense action through n very limited space is required to be produced by mcnns of a small lnovin= force. u#I ereI1 t names have been l~roposcd for this kind of mechanical ~OWW, but IIOIIC has yet obtnioctl, I bclicvc, a gcncrsl adoption. The term 6‘lo@ join/, ” is ncithcr good Knglish, nor in auy way appropriate lo the subject. The name of “ prgreasivc IevcP has StnlletilllCS bccll applieli to it; but from what has ~JrCC~lh~, it will be SW11 that it llils nothing ill commim with the ordiu:iry lever, and thou4 the latter may somctimcs bc cmploycil ns the metliunl through Whlc .‘I 1 lh moving force is appliell, yet it constitutes no csscntlal part or lllc machinr, any more than if applied to tlic rnidd]r “f a cord to iIlCIW%e the tCllsil~l1 ill the ITl]JC ?rluuhke. II1 rCfCrCnCe to tllc mode of uniting lh ~~latlcs by hixp, OKother equivalent means, I have proposed the term cortfitiril~ power, ntd to the lla&ulsr a~pnrAus above described, have1given the name of fric&o. 011 the ktflrience Of llre Air in determining tlic C~y.nt(&&ioj, of Saline Solutions. BIJ 'lhow.~s Gnnn~~,Es~. A. M. F. 12. s. ~..r ‘Tn_Ephenomenon rcfcrrcd to has long been known, and popularly enlnbWl in tlte cast of Glaubcr’s salt, without auy adcquatc es_
planation. A phial, or flask, is filled with a boiling AirtHtd y&; tion of sulphate of soda or Glauher’s salt, and its mouth immerKtfe$ stopped by a cork, or a piece of bladder is tied tightly over it, iphj < still hot. The solution, thus protected from the atmosphere, &e& rally cools without cr)stallizing, although it contains a great exeeae of salt, and continues Entirely liquid for hours, and even days. B& upon withdrawin g the stopper, or puncturing the bladder, and at& mitting air to the solution, it is immediately resolved into a spongy crystalline mass, with the evolution of much heat. The crystallization was attributed to the pressure of the atmosphere suddenly n& mitted, till it was shown that the same phenomenon occurred, whew air was admitted to a solution already subject to the atmospheric pressure. Recourse was likewise had to the supposed agency of solid particles floatin,.m in the air, and brought by means of it into contact with the solution; or it was supposed that the contact of gaseous molecules thcmselvrs might determine crystallization, as well as solid particles. But although the phenomenon has been the subject of much speculation among chemists, it is generally allowed that no satisfactory csplanation of it has yet been proposed. In experimenting upon this subject, it was found that hot concentrated solutions, in phials, or other receivers, might beinverted over mercury in the pneumatic trough, and still remain liquid on cooling; and thus the causes which determine crystallizatiou, were more readily examined. For this purpose, it was absolutely necessary that the mercury in the trough should be previously heated to llO” or 120’; for otherwise, that part of the solution in contact with the mercury cooled so rapidly, as to determine crystallization in .Phe lower part of the receiver, Ion* before the upper part had fallen30 In such cases, crystallization the temperature of the atmosp Piere. be inning on the surface of the mercury, advanced slowly and reAbove, there always remained a rgufarlp through the solution. tion o ’the solution too weak to crystallize, being impoveri$e (p”by It was also necessary to. the dense formation of crystals below. clean the lower and external part of the receivers, ,when’ .pl&e&%r the trough, from any adhering solution,, as a communicatioti sf @a& line matter was sometimes formed between the solution -in thb’F& When these precautions”“were ceiver and the atmosphere without. attended to, saline solutions over mercury remained as long wifho‘ut crystallizing, as when separated from the atmosphere in the usual mode. Solutions which completely filled the receivers when placed in the trough, allowed a portion of mercury to enter, by contracting materially as they cooled. A bubble of air could thus be thrown u without expelling any of the solution from the receiver, and t Re crystallizatron determined, without exposing the solution directly to the atmosphere. The first observation made, was, that solutions of sulphate of sodo sometimes did not crystallize at all upon the introduction of a hubThis irregularity was ble of air, or at least for a considerable time. chiefly observed in solutions formed at tcmperaturcs not exceedrng
360
Ofa the InJEuelzce of the Air in CrJjsluEEization.
1500 or ITO”, although water dissolves more of the sulphate of soda at, these inferior temperatures, than at a boiling heat. Brisk ebulli_ tion for a few seconds, however, rendered the solution upon cooling amendable to the usual influence of the air. In all successful cases, crystallization commenced in the upper part of. the receiver around the bubble of air, but pervaded the whole soj’utlon In a very few se_ A light glass bead was thrown up into a solution without conds. disturbing it. It occurred to me, that, since the effect of air could not he ac_ counted for on mechanical principles, it might arise from a certain Water always holds in solution cl~emical action upon the solution. a certain portion of air at the temperature of the atmosphere, which Cooled in a close vessel after boilivg, it parts with upon boiling. and then exposed to the atmosphere, it re-absorbs its usual proportion Now, this absorbed air ap ears to affect of air with great avidity. in a minute degree, the power of water to dissolve otfler bodies; at least, a considerable part of it is extricated upon the solution of salts. When a bubble of air is thrown up into a soluqion of sulpbate of soda, which has previously been ‘boded and deprived of all its air, a small quantity of air will certainly-be absorbed by the solution around the bubble. A slight reduction in the solvent power of the menstruum, will ensue at the spot where the air is dissolved. But the menstruum is greatly overloaded with saline matter, and ready to deposit it; the shghtest diminution of its solvent. power may, therefore, decide the precipitation or crystallization of the unnatural exThe absorption of air may, in this way, cess of saline matter. commence and determine the precipitation of the excess of sulphate of soda in solution. Here, too, we have an explanation of the fact just mentioned, that solutions of sulphate of soda which have not been boiled, are less affected b exposure to the air than well boiled solutions; for the former stk*71 retain the most of their air, and do not absorb air SO eagerly on exposure, as solutions which have been boiled. But the theory was most powerfully confirmed by an experimental examination of tbc influence of other gases, besides atmospheric air, Z?%eij*injluence was found to be prein determining crystallization. cisely p~oportmzate to the degree in whicl~ they are ahorBed OTdissolved by water cm1 the dine solutions. To a solution of sulphate of soda over mercury, which Ilad not been affected by a bubble of atmospheric air, a bubble of carbonic acid gas was added. Crystallization was instantly determined around the bubble, and thence through the whole mass. Water is capable of dissolving its own volume of carbonic acid gas, and a solution of sulphate of soda as strong as could be employed, was found by Saussure to absorb more than half its volume. In a solution of sulphate of soda, which was rather weak, both common air and carbonic acid gas failed to destroy the equilibrium; but a small bubble of ammoniacal gas instantly.determined crystallization. When gases arc employed which water dissolves abundantly, such
On some new mocks of Forming
f’y@$,i$,$~
381
3s ammoniacal and. sulphurous acid gases, the c~y.eial~iz$tiun procc& most vigorously. It is not deferred till..tjle bubble.6$$aa reaches the top of t$ receiver, as always happens with common.a!r, and frequently with carbo!ic acid gas; but the .tfack of the bubble bec_onlcs the common axis of innumerable crystalline planes, upon which It appears to be .borne upwards; and sometimes before the ascent is completed, the bubble is entangled and arrested by crystalline arrangements which precede it. Tllc number of gases which are less soluble in water !had atmodpheric air, is not considerable; but of these, hydrogen r was found to be decidedly least influential in determininlr cryeta Ilzatlon. Minute quantities of foreign liquids, soluble in water, likewise disposed the saline solution to irnmcdiate crystallization, M. might It is known be expected, and none with greater et&t than alcohol. that alcohol can precipitate sulphatc of soda from its nqueous solutions. The soluble gases I suppose to possess a similnr property. These facts appear to warrant the conclusion, that air tlctermiqes the crystallization of supersaturated saline solutions, by dissolving in the water, and thereby giving a shock to the feeble power by which the excess of salt is held in solution. ‘** Since the foregoing observations were printed, the author has percciyed that M. Gay-Lussnc! in his paper on crystallizatipn, (&L de Cl&z. tom. lxrxvil.) had distinctly thrown out the same theory as a conjecture, although the circumstance is nnt noticed by any But as M. Gag-Lusksc briu- forward systcmatlc chemical_wrlter. no esperimcntal illustration of the theory, and, indeed, a&luces’one esprriment as unfavourablc to it, the esperimental contirmdtiorj’of [Phil. ~fug. the theory is novel, and was certainly required.
Oa some nets mdes 0J formif&
Pyroplrorrrs.
By
M_.(#AT-Lussati . :-*.
M. tiAv-Lussrc,,in forming this substance, ubed.~i~lc~djSi~, black instead of liooey,or ROW, osually employed.’ ‘$:PotlishSlu& hunted with this form nf cnrbon, gave at first carbonic@id:sn phurous has, and nearly. in equal volumes; was obtalned nearly pure, and at last it was mixed withOosidd:of carbon, and this eventually prevailed. .‘rhe pytophorus B$ormed, burnt readily. M. tiay-Lussac is of ppinion, that carbon IS not necessary tv the combustion: he made a mixture of nearly 75 parts of alum, and 5.~5 of lamp-black, or 1 atom of the former and 5.5 atoms of the latter; and this mixture, when cslcined, at nearly a white heat, gave a reddish-brown product, contiiillillg, no traces of carbon, but it burnt very rfadily, and left ngrayiAwhttc Sulphate of is not cssentinl tci the preparation.
residuum.
Alum
riragnesia producc~ the same effect; sulphurct of l)otasGurn alone does nnt, hnwever, inllame spoofaneously in mass; and it occurred to M. Gil!-LUSsaC, that alumina, or magnesia, acted nw.rcl~ by llividing the s\\IllIlllret; that this WRS the C;ISC, was l~rovcd by sul>~~ltufin~ c\rarcorrl few them, 41; Vol.. ITI.--No. 5.-hlns, 1SZ).