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REPORT OF EXPERIMENTS ON THE EXPLOSIONS OF STEAM-BOILERS. 119 A fact noticed during the experiments on kept from fusion by a protecting film of oxide fusible alloys was again verified in these ex- there formed. periments; namely, that the mixtures of me. 5th. The thickness of the plate is not imtals require a considerable time to change portant, provided only that it is sufficiently their state of solidity or of fluidity; so that in strong to resist the pressure of the steam at the former case they may be heated above the temperatures below its point of fusion. true temperatures of Huidity, and in the lat- 6th. The temperature at which the plates ter case they may be cooled much below this are cast, and the rate of cooling of the cast temperature, without solidifying. The alloy metal, do not affect the temperature at which used in these experiments appears to have put the plates give vent to steam. the apparatus very fully upon its trial in this 7th. The effect stated in conclusion 3d is respect, and the experiments were performed explained by the nature of the alloys used, so rapidly as to give a further severe test. On which are formed of portions of different the occasion devoted to the trials when the fluidities; the more fluid parts are forced out steam was not urged up with its greatest ra- by the pressure of the steam, leaving the less pidity, the stem was drawn out at 268°, when fusible. These latter in general are burst, more rapidly at 270°, and with the fire at its not melted. maximum intensity, when the water 8th. By pressure in a receptable provided raised in temperature 24° in three minutes, with small openings, this effect of separating the stem was drawn out at 274o. In other the differently fluid portions of an alloy may experiments it gave way at 256o. The range be imitated. is 180 Fah., corresponding at ten atmo- 9th. Fusible alloys, used to indicate the spheres, to less than two atmospheres, under temperature of any part of a steam-boiler, the test of very severe comparisons. There should not be exposed to the pressure of the appears no reason to doubt, that when tested steam; at leisi, not in such a way that the by no more rigid modes than practice would separation of the differently fusible constifurnish, this apparatus would not only apply tuents of the alloys may be effected. as an alarm to prevent undue heating of the parts of the boiler, but as a manageable and
Fusing Points of Alloys applicable to u-eful check, in ordinary cases, upon the
The Committee next proceed to give the
results of their trials to determine metallic Conclusions.
alloys proper to be applied to steam boilers.
This problem admits, of course, of a great The conclusions deduced from the fore
variety of solutions. The metals used were going experiments on metallic alloys may be
limited to tin, lead, and bismuth; but still thus stated.
different mixtures of these may be made which Ist. The impurities of common lead, tin, will give alloys of the same fusing point. and bismuth, are usually not such as to affect The property which was most desirable in materially the fusing points of their alloys. these alloys was a small range of temperature
2d. When mixed in equivalent propor- in changing from the liquid to the solid state. tions, tin and lead formed alloys, not present- This property, it will be seen, is difficult to ing the characters of distinct chemical com- attain, and the less fusible alloys of the first pounds, in definite proportions. The alloys table, as well as the more fusible ones of the belween the range of one equivalent of tin to third, do not possess it. For the higher temone of lead, and one equivalent of tin to six of peratures, alloys of lead and tin are applicalead, varied considerably in the interval be- ble, and the question is reduced to an examitween the temperature of commencing to lose nation of the fusing points of different fluidity, and that at which a thermometer, mixtures. The greater proportions of lead immersed in the solidifying metal, became might be inferred to give the higher fusing stationary. These different alloys produced points, and the less proportions the lower pearly the same stationary temperature in a
Beginning with the alloy of equal thermometer plunged into the solidifying weights of tin and lead, the following table metal.
gives fusing points between 855° and 5030 3d. Fusible metal plates covered by a per- Fah. The stationary points were taken as forated metallie disk, and placed upon a already described; all the alloys in the table, steam-boiler, show signs of Auidity at the except the first, were hard before the station. disk before the steam has attained the tem- ary point occurred, and therefore this point perature of fusion of the alloy of which the inlicited, in these cases, some internal change plate is composed. This fiuid metal oozes in the solid, and did not correspond to tle through the perforations in the disk, and the passage from the liquid to the solid state. plate thus loses much of its substance before This seems not to have oceurred to Mr. finally giving vent to the steam.
Parke, who speaks of having taken this point 4th. The under parts of the plate are not as corresponding to that of congelation. It
REPORT OF EXPERIMENTS ON THE EXPLOSIONS OF STEAM-BOILERS.
3641* 352+ * Began above this point. + In these three cases the alloy
3537 congeals in thin plates, at the surface, and is a sandy solid 353below, at the sides. A liquid, with solid portions, at stationary
temperature. 3681 351 354* * Hardens in round masses, which, at the stationary point,
are surrounded by a liquid. 3664 352} *
352 * 353 353 352
1 12 16
The table of alloys by Parke, before referred to, gives a considerable variation in the melting points of the alloys in the above table. He makes the stationary point of the alloy of eight to eight, 3720 Fab.; that of eight lead and ten tin, 352°; that of eight lead to twelve tin, 336o ; this latter being the most fusible of the alloys of lead and tin. That the alloy, in equal parts, las not a fusing point varying much from that just given, the Committee were able to determine from various specimens of metal. With pure lead and grain tin, they found, for eig'it lead and nine tin, nearly the same as the fore
going, the stationary point to be, in different experiments, 355°, 356°, and 3551°. With one specimen of common lead the stationary point of an alloy of equal parts of lead and tin was 356° Fah. This lead melted at 606°, and the tin at 442. The Committee have no greater reason to suspect the accuracy of their other results. In all these cases the stationary point occurs when the metal begins to solidify.
It appears, then, by the foregoing table, that rery little change is effected in the fusing point of the alloy of equal parts of tio and lead, by increasing the quantity of the more
REPORT OF EXPERIMENTS ON THE EXPLOSIONS OF STEAM-BOILERS.
and had these characters impaired; the third had no stationary temperature above 400°, and lost its fluidity by slow degrees.
From perfect solidity to the greatest degree of fluidity of which the alloy was capable, required, in the case of the first alloy given above, about 70° of temperature: and between the temperature at which a solid could pierce the alloy, and the stationary temperature, was 8°. When the quantity of lead was doubled, the first interval was nearly 130°; and the interval between the temperatures of solidity and that at which the alloy could be penetrated easily, about 200
These facts show, that in using fusible alloys, those should be preferred wliich contain the smallest quantities of lead: a similar reason would lead to the preference of those cortaining the smallest proportions of bismuth.
Tin is nearly liquid at the stationary temperature; hardens by plates or small masses, and becomes entirely solid at this same temperature.
Experiments were made to ascertain what quantity of bismuth could be added to tin without destroying the property just described. To one hundred parts by weight, of tin, one part, five parts and ten parts of bismuth, re. spectively, were added. The first alloy melted at 4392°, and had the general characters of tin in hardening; the second melicd at 428°,
As it was thus shown that alloys of tin and bismuth presented no peculiar advantages, the alloys for temperatures below 355° Fah. were sought by combining the least quantity of bismuth which would give any requisite temperature with one of the alloys of the lable on p. 104. For this purpose the alloy of equal parts of tin and lead was selected. as having appropriate characters in its solidification, and melting at nearly as low a temperature as any of the others in the table. It does not, of course, follow, that this allow when com: bined with a given quantity of bismuth, will produce as low a fusing point as some other would; a question which, if it were worth deciding, experiment would determine. A few trials on this head were made by the Committee.
The following table gives the proportions of bismuth, which, added to an alloy of eight parts of tin and eight of lead, will give the temperature of the stationary points of an immersed thermometer between 355° and 326°. With the alloy which terminates this table the stationary temperature near the fusing point disappears, and another form of table is required for description,
REPORT OP EXPERIMENTS ON THE EXPLOSIONS OF STEAM-BOILERS.
TABLE II.-Alloys of Tin, Lead, and Bismuth, melting between 3550 and 326° Fah.
Table III.-Alloys losing fluidity between 3130 and 246° Fah.
The fusing points of the metals used in the foregoing alloys were, of the tin, 442° Fah., of the bismuth, 506", of the lead, 612o.
VI. To repeat the experiments of Klaproth, relating to the conversinn of water into stean, by highly heareil melal.
It being now well understood that an increase of temperature in a metallic surface may diminish the amount of vaporisation of a fluid placed upon it, the object of the following experiments was to study the phenomena at:ending the vaporisation of water by iron and copper, under different circumstances,
Ist. To ascertain the temperature at which a given small quantity of water will be veporised in the least time, by copper, with different states of surface.
2d. To ascertain the same point for iron, in similar circumstances.
3d. To extend these deductions to the ef. fect of introducing different quantities of water into copper or iron vessels, varying in thickness, in character of surface and heated by different sources, to various temperatures.
A number of bowls, of these different metals, of as nearly the same figure as could be obtained, and of different thicknesses, were
* Stationary ai 205o. I Sten dreiv olll in25. | Stem drew out at 235°.
# Srem drew out at 264°.
Stein drew out at 245°,
REPORT OF EXPERIMENTS ON THE EXPLOSIONS OF STEAM-BOILERS.
provided. The bowls were portions of spheres, of nearly three inches radius, and were eight in number, three being of copper and five of iron; four of these latter were of wrought, and one of cast-iron. For applying heat to the bowls. a cylindrical vessel containing oil, and another containing tin, were provided; the former was about nine inches in diameter and four high, and the latter six and a half inches in diameter and four high. These Vessels were heated by Mitchell's* alcohol lamp, or in the very high temperatures, by a charcoal furnace. The bowls were furnished with handles, which projecting, overlapped the edges of the cylinders, serving as baths for the oil and tin, and were thus kept in place.
The thermometers used in the experiments were carefully compared at the boiling point of water, and melting point of pure tin.
The experiments first to be detailed refer to the vaporisation of drops of water in copper
bowls of different states of surface, from the smooth polish to the roughness of oxidation. Vaporisation of Drops of Water by
Copper. 1. The bowl, No. VII., of copper, seren hundredths of an inch thick, was polished, but not very highly, and then placed in the tin bath while Anid; the tin, on solidifyini, kept the bowl in its place. The thermometer was placed in a small cylinder of thin sheetiron, containing mercury, the cylinder being as near the cup as possible. As the experiments progressed, the surface of the bowl became, of course, more and more tarnished; and after the two series of results recorded below were obtained, a third showed a marked etfect from the oxidation, by the increased vaporisation. One hundred and twenty drops, nearly, from the tube used, made up oneeighth of a fluid ounce; the weight of one drop was, therefore, about ·47 of a grain.
• A very convenient alcoho! lamp, with a dranght throngli the wick, and a separation between the alco. bol reservoir and the wick. The invention of Dr.J K. Mitchell.
+ In this and other tables, the series marked descending, are those obtained when the temperature was alling; the ascending series were obtained while the temperature of the bath was rising.