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On the probable cause of those explosions of steam boilers called fulminating
Mechanics,
Phyeics,
and Chemistry.
steel, fitted closely together, and drawn still closer by the riveted bolt, which will not let them part till the cutting of the latter is completed. I shall have thus, I hope, e&ablished my two positions, that the catch cannot be disengaged by accident, and that it cannot fail being disen aged in a case of ,over-winding. I am happy to be able to add that P have not, secured the disengaging catch by patent.
Tmnalhd
for the Journal of the Franklin Iaatitute.
On the Probable Cause of those Explosions of Steam Boilers Eulminating. Academy of Sciences of Paris. Under this title, a note of which is as follows :-
was
presented
by M. Mangin,
called
the substance
It results from the admirable experiments of M. Dufour, that the temperature of water may, under certain circumstances, be brought to 17EV’Cent. (352.5’ Fah.), without the production of boiling. These circumstances are the insulation from contact with the vessel, and insulation from contact with the air. Ebullition is produced by contact with a solid, that is, by the disturbance of the molecular equilibrium, and there is then a sudden evolution of steam. Nevertheless, every solid contact is not equally efficient in producing this change of state, and it results from the experiments of M. Dufour that isolation from contact with the vessel is not absolutely necessary for the production of the phenomenon. What appears to be indispensable is that the water shall be deprived of air, that the operation shall be carried on slowly, and that the heated mass shall be withdrawn from external Having explained these preliminaries, let us see diaturbing causes. how the explosions called fdminating are to be explained. These explosions take place only when the machine has been for a greater or less time at rest, and generally at the moment when they are about to resume the movement of the machine; and the boiler by its complete quietness gives no indication of the event. It is enough to open the throttle-valve, or one of the gauge-cocks, or the door of the furnace or ash-pit, or, in fact, any disturbance of the unstable equilibrium which has been established, to decide the catastrophe. It has also been remarked that, before the explosion, the pressure in the boiler is rather low than high. What, then, has taken place? When the machine was stopped, the pumps were also stopped; the furnace and ash-pit doors were closed, as were all the escapea for steam The ebullition continued, the safety-valve acted, and the or water. water which had recently been pumped in, was purged from air. Then when the activity of the fire had fallen sufficiently, the valve fell into its seat, and the apparatus assumed a state of repose. If the atmosphere was calm, the draft null, and the escapes of water and steam hermetically closed, the apparatus (allow me to use the figure) has gone to sleep, and the molecules of water being at rest, the temperature has gradually been raised to a point notably above that of evagoration under the existing pressure. AB the water produces no steam,
h
th6 &&fi$eatiori
of CarbGc
Acid.
401
that preaeure m8y be xnd may keep below thst neceseary for the LQ tion of the s8f&y-V8lVe. Things being in this condition, let any o8nw whatever disturb the equilibrium of the molecules, and 811 the he8t stored up in the liquid mass is instantly employed in producing an enormous volume of steam, while the m8ss of water not evaporated falls to the temperrrture correspondiffg to its pressure. Figures will easily account for the violence of the explosion which takes place. Let us suppose, in fact, that the pressure in the boiler, before the explosion, was 4 atmospheres, and that the temperstnre, in the quiescent state of the water, was only 170’ Cent. (358’ Fah.) As at 4 atmospheres the temperature of the water and ste8m is.145” Cent. (29P Fah.), each kilogramme of water in the boiler contains 25 units of beet above its normal quantity. Therefore, the moment this heat wtl~s liberated, it must have converted into steam 606S5+o_3,$!X.145 - 1G or nearly &th of a kilogramme of water; that is, about one-twentieth of the mass of water in the boiler was suddenly converted into ateam. Now, if we suppose that the volume of water in the boiler was double that of the steam, a quantity of water equal to one-tenth of the volume of the stesm is suddenly vaporized; and as, at a pressure of 4 atmospheres, 1 volume of water produces 477 volumes of steam, the volume of the steam will be increased 47 times, and the pressure will be 188 atmospheres. It will be conceived that against such generations of steam, the safety-valves are of no effect, and that the explosions are really fulminating. This manner of looking at the phenomenon leads to the suggestion of the following preceutions. To prevent the torpor of the water, let the boiler be so arranged that there shall be a constant circulation kept up by the difference of temperatures of different parts. A second precaution easily taken is never to close a boiler when at rest, hermetically, but to keep the safety-valve slightly raised, or a steam-uook 8 little open, so that a small quantity of steam may always be forming. . On the Solidijicatioa
of Carbonic Acid.
By MM. A. Loxa 8nd Cn. DRION. Vrwm the londonCheai~lNOW, No.64. In 8 paper read before the Academy, June 2, 1860, we stated tl& atmospheric pressure liquefies csrbonic acid when-its tempersture $8 reduced to the point 8t which liquid ammoni8 evaporates in vacua. By slightly modifying the conditions of the experiment, we hsve sucaeeded in solidifying csrbonic acid with the aid of an apparatus 8s simple This hitherto danas those daily employed in chemical laboratories. gerous and costly operation may in future be easily repeated to a ohemica1 class. If liquid ammonin is introduced into a glass globe, and the interior of this put in communication with 8 good sir-pump, by the intervention of a vessel containing coke impregnated with sulphuric acid, t.he 34’
Phyeics,
and Chemistry.
steel, fitted closely together, and drawn still closer by the riveted bolt, which will not let them part till the cutting of the latter is completed. I shall have thus, I hope, e&ablished my two positions, that the catch cannot be disengaged by accident, and that it cannot fail being disen aged in a case of ,over-winding. I am happy to be able to add that P have not, secured the disengaging catch by patent.
Tmnalhd
for the Journal of the Franklin Iaatitute.
On the Probable Cause of those Explosions of Steam Boilers Eulminating. Academy of Sciences of Paris. Under this title, a note of which is as follows :-
was
presented
by M. Mangin,
called
the substance
It results from the admirable experiments of M. Dufour, that the temperature of water may, under certain circumstances, be brought to 17EV’Cent. (352.5’ Fah.), without the production of boiling. These circumstances are the insulation from contact with the vessel, and insulation from contact with the air. Ebullition is produced by contact with a solid, that is, by the disturbance of the molecular equilibrium, and there is then a sudden evolution of steam. Nevertheless, every solid contact is not equally efficient in producing this change of state, and it results from the experiments of M. Dufour that isolation from contact with the vessel is not absolutely necessary for the production of the phenomenon. What appears to be indispensable is that the water shall be deprived of air, that the operation shall be carried on slowly, and that the heated mass shall be withdrawn from external Having explained these preliminaries, let us see diaturbing causes. how the explosions called fdminating are to be explained. These explosions take place only when the machine has been for a greater or less time at rest, and generally at the moment when they are about to resume the movement of the machine; and the boiler by its complete quietness gives no indication of the event. It is enough to open the throttle-valve, or one of the gauge-cocks, or the door of the furnace or ash-pit, or, in fact, any disturbance of the unstable equilibrium which has been established, to decide the catastrophe. It has also been remarked that, before the explosion, the pressure in the boiler is rather low than high. What, then, has taken place? When the machine was stopped, the pumps were also stopped; the furnace and ash-pit doors were closed, as were all the escapea for steam The ebullition continued, the safety-valve acted, and the or water. water which had recently been pumped in, was purged from air. Then when the activity of the fire had fallen sufficiently, the valve fell into its seat, and the apparatus assumed a state of repose. If the atmosphere was calm, the draft null, and the escapes of water and steam hermetically closed, the apparatus (allow me to use the figure) has gone to sleep, and the molecules of water being at rest, the temperature has gradually been raised to a point notably above that of evagoration under the existing pressure. AB the water produces no steam,
h
th6 &&fi$eatiori
of CarbGc
Acid.
401
that preaeure m8y be xnd may keep below thst neceseary for the LQ tion of the s8f&y-V8lVe. Things being in this condition, let any o8nw whatever disturb the equilibrium of the molecules, and 811 the he8t stored up in the liquid mass is instantly employed in producing an enormous volume of steam, while the m8ss of water not evaporated falls to the temperrrture correspondiffg to its pressure. Figures will easily account for the violence of the explosion which takes place. Let us suppose, in fact, that the pressure in the boiler, before the explosion, was 4 atmospheres, and that the temperstnre, in the quiescent state of the water, was only 170’ Cent. (358’ Fah.) As at 4 atmospheres the temperature of the water and ste8m is.145” Cent. (29P Fah.), each kilogramme of water in the boiler contains 25 units of beet above its normal quantity. Therefore, the moment this heat wtl~s liberated, it must have converted into steam 606S5+o_3,$!X.145 - 1G or nearly &th of a kilogramme of water; that is, about one-twentieth of the mass of water in the boiler was suddenly converted into ateam. Now, if we suppose that the volume of water in the boiler was double that of the steam, a quantity of water equal to one-tenth of the volume of the stesm is suddenly vaporized; and as, at a pressure of 4 atmospheres, 1 volume of water produces 477 volumes of steam, the volume of the steam will be increased 47 times, and the pressure will be 188 atmospheres. It will be conceived that against such generations of steam, the safety-valves are of no effect, and that the explosions are really fulminating. This manner of looking at the phenomenon leads to the suggestion of the following preceutions. To prevent the torpor of the water, let the boiler be so arranged that there shall be a constant circulation kept up by the difference of temperatures of different parts. A second precaution easily taken is never to close a boiler when at rest, hermetically, but to keep the safety-valve slightly raised, or a steam-uook 8 little open, so that a small quantity of steam may always be forming. . On the Solidijicatioa
of Carbonic Acid.
By MM. A. Loxa 8nd Cn. DRION. Vrwm the londonCheai~lNOW, No.64. In 8 paper read before the Academy, June 2, 1860, we stated tl& atmospheric pressure liquefies csrbonic acid when-its tempersture $8 reduced to the point 8t which liquid ammoni8 evaporates in vacua. By slightly modifying the conditions of the experiment, we hsve sucaeeded in solidifying csrbonic acid with the aid of an apparatus 8s simple This hitherto danas those daily employed in chemical laboratories. gerous and costly operation may in future be easily repeated to a ohemica1 class. If liquid ammonin is introduced into a glass globe, and the interior of this put in communication with 8 good sir-pump, by the intervention of a vessel containing coke impregnated with sulphuric acid, t.he 34’