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Article THE CHEMISTRY OF COMMON THINGS. ← Page 6 of 7 →
Note: This text has been automatically extracted via Optical Character Recognition (OCR) software.
The Chemistry Of Common Things.
temperature of the waters in which the two hands are respectively immersed , although there is in reality a difference of from one hundred to one Hundred and fifty degrees , or more , between them . Let the hands be now both withdrawn from the first and third glasses , and placed in the middle one , a sensation of heat will be perceived in the left hand , and one of cold in the right . Thus the same body of water ,
all parts of which must necessarily be of the same temperature , actually conveys a perception of heat and cold at the same time , when the impression Is received by different hands . This result may be made to appear the more striking if the hands be at first both placed in the lukewarm water , without first exposing them to different temperatures . If the water is at about 96 or 98 ° , no sensation either of
heat or cold will be experienced , and when the water becomes perfectly still there will he being in contact with the hands ; but if the hands be removed to the end glasses , and again transferred to the middle one ^ the same water , which before conveyed no impression either of heat or cold , will now convey impressions of both to different hands .
If we touch different ohgects in a rooin which is at an even tampe * rature , we shall obtain very different perceptions from each . Supposing the room to be at an ordinary temperature , and without afire , if we place our hand on the carpet , or table cloth , it will feel neither warm nor cold ; the paper on the walls will feel slightly cool ; the woodwork of the doors , shutters , and furniture , colder ; th e marble
chimney pieces colder still ; and the fire irons , handles of the doors , & c , coldest of all . If we go into a room , the heat of which is considerably above that of the body , we shall find the same difference in the apparent temperature of the objects , but in an inverse order . The carpet , & c , will feel scarcely wanner than before , but the other objects will all feel warm in the same order as their coldness in the former case—the marble and metal being now hottest . Metals give
off their heat with much greater rapidity ^ than any other substances ; and care should be taken against touching them when highly heated , For this reason , silver or metal teapots are rarely or never made with a solid handle of the same metal—the handle is made hollow , and two pieces of some non-conducting substance are interposed between the ends of the handle and the body of the teapot . But little of the heat from the teapot can reach the handle through the nonconductors , and this little is incapable of collecting there in large quantities ,
the heat being constantly carried off by the air in contact with the surface . Thus the heat is dissipated almost as fast as it is received , and the handle never becomes inconveniently warm . These phenomena will explain themselves when the cause of the sensation of heat and cold is considered . The human body possesses
at all times and in all conditions a uniform temperature of about 98 ° . Whenever , by being placed in contact with a cold object , the heat from any part of the body is abstracted faster than it can be generated , a feeling of cold is produced , When , on the other hand , the ordinary
Note: This text has been automatically extracted via Optical Character Recognition (OCR) software.
The Chemistry Of Common Things.
temperature of the waters in which the two hands are respectively immersed , although there is in reality a difference of from one hundred to one Hundred and fifty degrees , or more , between them . Let the hands be now both withdrawn from the first and third glasses , and placed in the middle one , a sensation of heat will be perceived in the left hand , and one of cold in the right . Thus the same body of water ,
all parts of which must necessarily be of the same temperature , actually conveys a perception of heat and cold at the same time , when the impression Is received by different hands . This result may be made to appear the more striking if the hands be at first both placed in the lukewarm water , without first exposing them to different temperatures . If the water is at about 96 or 98 ° , no sensation either of
heat or cold will be experienced , and when the water becomes perfectly still there will he being in contact with the hands ; but if the hands be removed to the end glasses , and again transferred to the middle one ^ the same water , which before conveyed no impression either of heat or cold , will now convey impressions of both to different hands .
If we touch different ohgects in a rooin which is at an even tampe * rature , we shall obtain very different perceptions from each . Supposing the room to be at an ordinary temperature , and without afire , if we place our hand on the carpet , or table cloth , it will feel neither warm nor cold ; the paper on the walls will feel slightly cool ; the woodwork of the doors , shutters , and furniture , colder ; th e marble
chimney pieces colder still ; and the fire irons , handles of the doors , & c , coldest of all . If we go into a room , the heat of which is considerably above that of the body , we shall find the same difference in the apparent temperature of the objects , but in an inverse order . The carpet , & c , will feel scarcely wanner than before , but the other objects will all feel warm in the same order as their coldness in the former case—the marble and metal being now hottest . Metals give
off their heat with much greater rapidity ^ than any other substances ; and care should be taken against touching them when highly heated , For this reason , silver or metal teapots are rarely or never made with a solid handle of the same metal—the handle is made hollow , and two pieces of some non-conducting substance are interposed between the ends of the handle and the body of the teapot . But little of the heat from the teapot can reach the handle through the nonconductors , and this little is incapable of collecting there in large quantities ,
the heat being constantly carried off by the air in contact with the surface . Thus the heat is dissipated almost as fast as it is received , and the handle never becomes inconveniently warm . These phenomena will explain themselves when the cause of the sensation of heat and cold is considered . The human body possesses
at all times and in all conditions a uniform temperature of about 98 ° . Whenever , by being placed in contact with a cold object , the heat from any part of the body is abstracted faster than it can be generated , a feeling of cold is produced , When , on the other hand , the ordinary