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Article THE CHEMISTRY OF COMMON. THINGS. ← Page 6 of 9 →
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The Chemistry Of Common. Things.
sorbed sufficient to raise the water , did it continue in the liquid form , to a temperature equal to that of red-hot iron . When , after a heavy fell of - snow , a thaw ensues , we frequently see the snow lying about for several days , instead of instantly rushing into water the moment the temperature of the air rose above 32 ° , as it would were it not for the absorption of heat during the process of liquefaction ; but no explanation seems to have been offered of the phenomenon , until Br . Black explained it by experiments similar to those above described . Were there not this absorption , the moment a frost occurred , every drop of water would be converted
into ice , entailing the most serious consequences ; and directly wafer was heated to the boiling point , it would instantly become _ steam , in the same mariner as gunpowder is converted into smoke , but with , far more destructive effects , It thus appears that heat is capable of existing in two conditions ; in . one of which it is apparent to the senses , and may be measured by
the thermometer , in which form it is called sensible heat . In this state it is uiicombihed with the particles of matter , and is consequently often termedjfy ee heat . In the other it is combined with the particles of matter , and is insensible to the usual tests . It is therefore called latent heat . As it may be proved that solid bodies contain latent heat as well as liquids and gases , we possess no means of ascertaining the actual amount of heat contained in bodies . When latent heat is
liberated from the particles with which it is combined , it becomes sensible , and occasions a rise of temperature . When sulphuric acid and water are mixed in certain proportions , the mixture rises to several degrees above boiling water . This rise has been bv some ascribed to the liberation of a portion of the latent heat ; but it
may likewise be accounted for by supposing a change m the specific heat of the compound , as will be shown hereafter Specific Heat , or Capacity for Heat . —As the force of gravity exercises an unequal effect upon equal volumes of different substances ,, constituting ; specific gravity , so the effect of heat in regard to
temperature varies with the nature of tlie substances , giving rise to specific heat . The same amount of heat which is sufficient to-raise a given , weight of water one degree , will raise the same weight of mercury thirty degrees , If a quantity of water at 81 ° be mixed with an . equal weight of mercury at 50 ° , the temperature of the mixture will become 80 ° . In . this instance , it appears that the water has lost one degree only , while'the mercury has gained thirty degrees .
The specific heat of bodies is usually determined by the quantity of ice which they would melt in tailing through one degree of the thermometric scale . It has already been shown that water in cooling 140 ° , gives out sufficient heat to melt an equal weight of ice . In cooling through one degree only , therefore , it will melt 1 * 140 th of its wei ght of ice . Thus , 140 , 000 grains of water when cooled 1 ° , will xnelt 1000 grains of ice , while the same weight of mercury will , under . similar circumstances , melt thirty-three grains only , As the
Note: This text has been automatically extracted via Optical Character Recognition (OCR) software.
The Chemistry Of Common. Things.
sorbed sufficient to raise the water , did it continue in the liquid form , to a temperature equal to that of red-hot iron . When , after a heavy fell of - snow , a thaw ensues , we frequently see the snow lying about for several days , instead of instantly rushing into water the moment the temperature of the air rose above 32 ° , as it would were it not for the absorption of heat during the process of liquefaction ; but no explanation seems to have been offered of the phenomenon , until Br . Black explained it by experiments similar to those above described . Were there not this absorption , the moment a frost occurred , every drop of water would be converted
into ice , entailing the most serious consequences ; and directly wafer was heated to the boiling point , it would instantly become _ steam , in the same mariner as gunpowder is converted into smoke , but with , far more destructive effects , It thus appears that heat is capable of existing in two conditions ; in . one of which it is apparent to the senses , and may be measured by
the thermometer , in which form it is called sensible heat . In this state it is uiicombihed with the particles of matter , and is consequently often termedjfy ee heat . In the other it is combined with the particles of matter , and is insensible to the usual tests . It is therefore called latent heat . As it may be proved that solid bodies contain latent heat as well as liquids and gases , we possess no means of ascertaining the actual amount of heat contained in bodies . When latent heat is
liberated from the particles with which it is combined , it becomes sensible , and occasions a rise of temperature . When sulphuric acid and water are mixed in certain proportions , the mixture rises to several degrees above boiling water . This rise has been bv some ascribed to the liberation of a portion of the latent heat ; but it
may likewise be accounted for by supposing a change m the specific heat of the compound , as will be shown hereafter Specific Heat , or Capacity for Heat . —As the force of gravity exercises an unequal effect upon equal volumes of different substances ,, constituting ; specific gravity , so the effect of heat in regard to
temperature varies with the nature of tlie substances , giving rise to specific heat . The same amount of heat which is sufficient to-raise a given , weight of water one degree , will raise the same weight of mercury thirty degrees , If a quantity of water at 81 ° be mixed with an . equal weight of mercury at 50 ° , the temperature of the mixture will become 80 ° . In . this instance , it appears that the water has lost one degree only , while'the mercury has gained thirty degrees .
The specific heat of bodies is usually determined by the quantity of ice which they would melt in tailing through one degree of the thermometric scale . It has already been shown that water in cooling 140 ° , gives out sufficient heat to melt an equal weight of ice . In cooling through one degree only , therefore , it will melt 1 * 140 th of its wei ght of ice . Thus , 140 , 000 grains of water when cooled 1 ° , will xnelt 1000 grains of ice , while the same weight of mercury will , under . similar circumstances , melt thirty-three grains only , As the