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On the air engine
,air Engine.
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sea or ordinary water; the discovery of this fact suggested the experiments on the application of brine.as a preserver of iron. T h e object of the last set of experiments was to determine, b y trial, the rates of corrosion of metals in fresh water, sea water, and saturated brine. The results demonstrated that sea water corrodes the quickest, fresh water less rapidly, and brine very much slower than either. The circumstance was incidentally mentioned of the use of common salt for preserving ships' timbers, for which purposes the spaces between the ribs of some of the North American ships are frequently packed with rock salt, and the effect has proved advantageous to the duration of the timber, without affecting the metal fastenings, as would have been supposed.--Proceed. Inst. Cir. Eng. Athemeum.
On the .air Engine. By MR. J. STIRT.I~a. The paper read was by Mr. J. Stirling, and described an Air Engine, invented by his brother and himself. The movements are founded on the well-known pneumatic principle, that air has its bulk or pressure increased or diminished in proportion as its temperature is raised or lowered. The application of this principle was exemplified by drawings, and a model exhibiting a machine composed of two stron~ tight air vessels, connected with the opposite ends of a vertical cylinder, in which a piston works in the usual manner. Within these air vessels are suspended two air-tight vessels, or plungers, filled with non-conducting substances, and attached to the opposite extremities of a beam, capable of moving up and down alternately, to the extent of one-fifth of the depth of the air-vessels. By this motion of the plunger, the air which is in a heated state below is moved to the upper part of tile vessel, and in its transit traverses a series of vertical capillary passages between three metalic plates, which absorb the major part of the caloric. The remaindei" is taken up by a refrigerator of tubes filled with water. The air at the heated end is about 700 degrees, and has a proportionate pressure ; when it arrives at the cooled end it is reduced to about ] 50 degrees, and the pressure diminished to a corresponding extent. Thet'efbre, as the internal vessels move in opposite directions, it necessarily follows that the pressure of the condensed air in one vessel is increased, while that of the other is diminished. A difference of pressure is thus produced upon the opposite ends of the piston, and a reciprocating motion resuits, which communicates through a beam, connecting rod, crank, and fly-wheel to the machinery when driven. Machines on this principle were stated to have been worked, for some years past, at Dundee, with considerable savinu of fuel, as compared to a steamengine of similar power, and "doi"ng the same work. It is now proposed to adapt it to marine purposes, to which, from its simplicity and slight expenditure of fuel, it appeared well fitted. Ibid.
202
Mechanics, Physics, and Chemistry.
On Be~zoline. By'Dla. F o w ~ . s . Pure oil of bitter almonds is converted, by the action of a strong solution of ammonia, into a solid white substance, having a crystalline form, and which was termed by M. Laurent hydrobenzamide. The author found that this substance, by the further action of alkalies, became harder and less fusible than before, and not differing in chemical composition from the original substance, but exhibiting the properties of an organic salt-base. To this substance the author gives the name of Benzoline. He finds that the salts which it forms by combinations wid~ acids are, in general, remarkable tbr their sparing solubility, and that many of them, as the hydrochlorate, the nitrate, and the sulphate, are crystallizable ; of the properties of these salts the author gives a detailed aeeount.--Proceed. Royal Society. Ibid. On the Solubility of Oxide of Lead in Pure Water.
By Lieut. Col. PnILI~ Yoi~x~. It is from this property that leaden pipes and cisterns become dangerous, when the water which fills them is soft and pure. The lead, however, whieh the water lakes up may be removed by filtering the water through paper ; a circumstance which has been explained by supposing that the oxide of lead is not really dissolved in the water," but merely suspended in it. The author, however, shows that the oxide of lead is taken up by the substance of the paper and combines with it, from an affinity such as subsists between the same metallic oxide and cotton fibre; the ['ast taking the oxide fl'om solution in lime-water, and lead being often fixed as a mordant on cloth tor dyeing in this way, according to the statement of Mr. Crum. He finds also that the power of the filter may be exhausted, and that therefore it would be unsafe to trust to the action of a filter to separate oxide of lead i¥om water for an unlimited time.~Proc. Chem. 5"oc. Ibid. Experime~ts on Ozone.
By Ma. WIgLIA~SO~-.
The name ozone was given by SchSnbein to tile substance which occasions the peculiar smell possessed by oxygen gas when produced by the x;oitaie decomposition of water, and he has made it the subject of much ingenious speculation, concluding that it is a new elementary body, and that it is derived from the decomposition of nitrogen, supposed to be of a compound nature. The last of these opinions, however, has already been disproved by Marignac, who demonstrated that the ozone odor was produced by the decomposition of water free from nitrogen. Mr. Williamson's experiments go to prove that ozone is a compound body, and that one of its elements is hydrogen ; for having excluded the last element from any other source, by obtaining the oxygen gas with ozone from the decomposition of a salt of copper, a process in which no hydrogen is generated, and passing the oxygen over metallic copper which had been reduced by carbonic
201
sea or ordinary water; the discovery of this fact suggested the experiments on the application of brine.as a preserver of iron. T h e object of the last set of experiments was to determine, b y trial, the rates of corrosion of metals in fresh water, sea water, and saturated brine. The results demonstrated that sea water corrodes the quickest, fresh water less rapidly, and brine very much slower than either. The circumstance was incidentally mentioned of the use of common salt for preserving ships' timbers, for which purposes the spaces between the ribs of some of the North American ships are frequently packed with rock salt, and the effect has proved advantageous to the duration of the timber, without affecting the metal fastenings, as would have been supposed.--Proceed. Inst. Cir. Eng. Athemeum.
On the .air Engine. By MR. J. STIRT.I~a. The paper read was by Mr. J. Stirling, and described an Air Engine, invented by his brother and himself. The movements are founded on the well-known pneumatic principle, that air has its bulk or pressure increased or diminished in proportion as its temperature is raised or lowered. The application of this principle was exemplified by drawings, and a model exhibiting a machine composed of two stron~ tight air vessels, connected with the opposite ends of a vertical cylinder, in which a piston works in the usual manner. Within these air vessels are suspended two air-tight vessels, or plungers, filled with non-conducting substances, and attached to the opposite extremities of a beam, capable of moving up and down alternately, to the extent of one-fifth of the depth of the air-vessels. By this motion of the plunger, the air which is in a heated state below is moved to the upper part of tile vessel, and in its transit traverses a series of vertical capillary passages between three metalic plates, which absorb the major part of the caloric. The remaindei" is taken up by a refrigerator of tubes filled with water. The air at the heated end is about 700 degrees, and has a proportionate pressure ; when it arrives at the cooled end it is reduced to about ] 50 degrees, and the pressure diminished to a corresponding extent. Thet'efbre, as the internal vessels move in opposite directions, it necessarily follows that the pressure of the condensed air in one vessel is increased, while that of the other is diminished. A difference of pressure is thus produced upon the opposite ends of the piston, and a reciprocating motion resuits, which communicates through a beam, connecting rod, crank, and fly-wheel to the machinery when driven. Machines on this principle were stated to have been worked, for some years past, at Dundee, with considerable savinu of fuel, as compared to a steamengine of similar power, and "doi"ng the same work. It is now proposed to adapt it to marine purposes, to which, from its simplicity and slight expenditure of fuel, it appeared well fitted. Ibid.
202
Mechanics, Physics, and Chemistry.
On Be~zoline. By'Dla. F o w ~ . s . Pure oil of bitter almonds is converted, by the action of a strong solution of ammonia, into a solid white substance, having a crystalline form, and which was termed by M. Laurent hydrobenzamide. The author found that this substance, by the further action of alkalies, became harder and less fusible than before, and not differing in chemical composition from the original substance, but exhibiting the properties of an organic salt-base. To this substance the author gives the name of Benzoline. He finds that the salts which it forms by combinations wid~ acids are, in general, remarkable tbr their sparing solubility, and that many of them, as the hydrochlorate, the nitrate, and the sulphate, are crystallizable ; of the properties of these salts the author gives a detailed aeeount.--Proceed. Royal Society. Ibid. On the Solubility of Oxide of Lead in Pure Water.
By Lieut. Col. PnILI~ Yoi~x~. It is from this property that leaden pipes and cisterns become dangerous, when the water which fills them is soft and pure. The lead, however, whieh the water lakes up may be removed by filtering the water through paper ; a circumstance which has been explained by supposing that the oxide of lead is not really dissolved in the water," but merely suspended in it. The author, however, shows that the oxide of lead is taken up by the substance of the paper and combines with it, from an affinity such as subsists between the same metallic oxide and cotton fibre; the ['ast taking the oxide fl'om solution in lime-water, and lead being often fixed as a mordant on cloth tor dyeing in this way, according to the statement of Mr. Crum. He finds also that the power of the filter may be exhausted, and that therefore it would be unsafe to trust to the action of a filter to separate oxide of lead i¥om water for an unlimited time.~Proc. Chem. 5"oc. Ibid. Experime~ts on Ozone.
By Ma. WIgLIA~SO~-.
The name ozone was given by SchSnbein to tile substance which occasions the peculiar smell possessed by oxygen gas when produced by the x;oitaie decomposition of water, and he has made it the subject of much ingenious speculation, concluding that it is a new elementary body, and that it is derived from the decomposition of nitrogen, supposed to be of a compound nature. The last of these opinions, however, has already been disproved by Marignac, who demonstrated that the ozone odor was produced by the decomposition of water free from nitrogen. Mr. Williamson's experiments go to prove that ozone is a compound body, and that one of its elements is hydrogen ; for having excluded the last element from any other source, by obtaining the oxygen gas with ozone from the decomposition of a salt of copper, a process in which no hydrogen is generated, and passing the oxygen over metallic copper which had been reduced by carbonic