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Article THE CHEMISTRY OF COMMON THINGS, ← Page 2 of 5 →
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The Chemistry Of Common Things,
formed requires less latent heat than did its constituents when they were separate . In such a case , therefore , the superfltiotis : heat is discharged , and becomes sensible , raising the body to a higher temperature . When , for instance , sulphuric acid is mixed with water , in the proportion of one part of acid to four of water , the mixture becomes many degrees hotter than boiling water , owing to the latent heat evolved .
In this case both the substances combined ai-e liquids , but in general two bodies will not unite at ordinary temperatures unless one or both of them are in the liquid state , but when this requirement is not fulfilled , they may afterwards be combined by the application of heat . Thus if one volume of oxygen be mixed with two of hydrogen , they will not unite , but if flame , or the electric spark be applied , or the mixture be raised to a red heat , they will instantly combine with a loud noise ,
giving out light and heat . The oxygen and hydrogen each contaitis when separate , a certain quantity of heat , hut the water , or rather vapour , which results from their union , requires much less than the sum of these quantities . Part of the latent heat is , therefore , converted
into sensible heat , and , for the moment , raises the temperature of the compound gas to whiteness . Part of the gases are combined by the heat of the applied spark or flame , and their combination evolves sufficient heat to effect the union of the next portions , and in this manner the whole of the gases are combined .
It is by the combination oi these gases that all the common iorms of artificial light are produced , the gases being gradually brought together instead of being presented to one another en maw , as in the former instance . The combination is , therefore , gradual instead of being instantaneous , and a continuous flame is the result , instead of an explosion . Hydrogen enters largely into the composition of most combustible bodies , such as wax , fat , tallow , oil , and coal gas ,
and oxygen forms a fifth part of the atmosphere ; it is from the union of these two that the flame of a candle , lamp , or gas-light is produced . The hydrogen is obtained from the decomposition of the substance burnt , for bodies may be decomposed , as well as combined , by heat . Thus wax , tallow , oil , & c , are decomposed by a red heat , into their constituent elements , hydrogen and carbon . But it will require a greater heat than this to combine these gases with' tlie oxygen of the
atmosphere . Now let us mark the successive changes that take place in the flame of a candle . The wick being lighted , its heat first melts the substance of the caudle , then decomposes it into its constituent ' gases , and afterwards combines these gases with the oxygen of the atrhosphere . The heat thus evolved , produces the bright red-hot spot seen at the
extremity of the wick , and also renders the gases and the compounds produced by them incandescent , or white hot , and this body of incandescent gas is the flame . The part of the candle immediately around the wick is kept in a state of fusion by the heat of the flame , and rises by capillary attraction to the top of the wick , where it is decomposed by the red hot spot , which , however , is not sufficiently
Note: This text has been automatically extracted via Optical Character Recognition (OCR) software.
The Chemistry Of Common Things,
formed requires less latent heat than did its constituents when they were separate . In such a case , therefore , the superfltiotis : heat is discharged , and becomes sensible , raising the body to a higher temperature . When , for instance , sulphuric acid is mixed with water , in the proportion of one part of acid to four of water , the mixture becomes many degrees hotter than boiling water , owing to the latent heat evolved .
In this case both the substances combined ai-e liquids , but in general two bodies will not unite at ordinary temperatures unless one or both of them are in the liquid state , but when this requirement is not fulfilled , they may afterwards be combined by the application of heat . Thus if one volume of oxygen be mixed with two of hydrogen , they will not unite , but if flame , or the electric spark be applied , or the mixture be raised to a red heat , they will instantly combine with a loud noise ,
giving out light and heat . The oxygen and hydrogen each contaitis when separate , a certain quantity of heat , hut the water , or rather vapour , which results from their union , requires much less than the sum of these quantities . Part of the latent heat is , therefore , converted
into sensible heat , and , for the moment , raises the temperature of the compound gas to whiteness . Part of the gases are combined by the heat of the applied spark or flame , and their combination evolves sufficient heat to effect the union of the next portions , and in this manner the whole of the gases are combined .
It is by the combination oi these gases that all the common iorms of artificial light are produced , the gases being gradually brought together instead of being presented to one another en maw , as in the former instance . The combination is , therefore , gradual instead of being instantaneous , and a continuous flame is the result , instead of an explosion . Hydrogen enters largely into the composition of most combustible bodies , such as wax , fat , tallow , oil , and coal gas ,
and oxygen forms a fifth part of the atmosphere ; it is from the union of these two that the flame of a candle , lamp , or gas-light is produced . The hydrogen is obtained from the decomposition of the substance burnt , for bodies may be decomposed , as well as combined , by heat . Thus wax , tallow , oil , & c , are decomposed by a red heat , into their constituent elements , hydrogen and carbon . But it will require a greater heat than this to combine these gases with' tlie oxygen of the
atmosphere . Now let us mark the successive changes that take place in the flame of a candle . The wick being lighted , its heat first melts the substance of the caudle , then decomposes it into its constituent ' gases , and afterwards combines these gases with the oxygen of the atrhosphere . The heat thus evolved , produces the bright red-hot spot seen at the
extremity of the wick , and also renders the gases and the compounds produced by them incandescent , or white hot , and this body of incandescent gas is the flame . The part of the candle immediately around the wick is kept in a state of fusion by the heat of the flame , and rises by capillary attraction to the top of the wick , where it is decomposed by the red hot spot , which , however , is not sufficiently