1869.] 



Resistance of Liquids. 



235 



experimental error are eliminated. If the two cones are brought into 

 actual contact, and water of a known temperature is led for a given time 

 through the upper cone, a certain thermal effect is produced in the lower 

 one. If the cones be then separated, and a liquid be interposed between 

 them, and if water of the same temperature as before be led for the same 

 time as before through the upper cone, a less thermal effect is produced. 

 The difference between the two effects is a measure of the resistance of the 

 liquid. Results so obtained have to be corrected for the varying pressure 

 to which the air in the lower cone is subjected as the water in the glass 

 tube sinks. To finds the absolute results in thermal units, we have to take 

 into account the diameter of the surface of the lower cone, its capacity, and 

 the specific heat of the air which is in it. 



The following are the chief results obtained : — 



(1) The connexion in the instance of water between the thickness and 

 the time required for the first-heat effect. 



(2) The connexion between the temperature and the time required for 

 the first-heat effect. It is shown that hotter water conducts heat better 

 than colder ; and that the hotter the conducting-water, the greater is the 

 difference in rate. 



(3) The connexion between the entire quantity of heat passing in a 

 given time and the thickness and temperature of the conducting-water. 



(4) The effect of the solution of various salts in altering the thermal 

 resistance of water. Every salt tried was found, when dissolved in water, 

 to increase its thermal resistance. The author submits that the effect of the 

 dissolved salt is chiefly, perhaps wholly, due to the displacement of a portion 

 of the water by a substance having greater resistance, and to the modifica- 

 tion in the specific heat of the liquid, caused by the introduction of the salt. 



(5) The resistance of the liquids in the following list was examined 

 under precisely similar circumstances. The thickness was in each case 

 1 millim. The initial temperature of the liquid was 20°'17C, and the 

 temperature-difference, AT, was 10°C. That is, the platinum surface of 



te upper cone was maintained at 30 o, l/C. The duration of the experi- 

 ment in each case was 1'. The numbers show the specific resistance under 

 the above circumstances, that is, the ratio between the quantities of heat 

 arrested by the several liquids and that arrested by water. 



Liquid. S - pe( f C 

 ^ resistance. 



Water 1- 



Glycerine 3-84 



Acetic acid (glacial) 8'38 



Acetone 8-51 



Oxalate of ethyl 8'85 



Sperin-oil 8 - 85 



Alcohol 9.08 



Acetate of ethyl 9 -08 



Nitrobenzol...'. 9*86 



Oxalate of amyl 10-06 



Butyric alcohol 10-00 



t • .-, Specific 

 Llc L lucL resistance. 



Acetate of amyl 10-00 



Arnylaniin 10-14 



Amylic alcohol 10*23 



Oil of turpentine 11 '75 



Nitrate of butyl 11-87 



Chloroform 12.10 



Bichloride of carbon 12-92 



Mercury amyl 12-92 



Bromide of ethylen 13*16 



Iodide of amyl 13-27 



Iodide of ethyl (?) ? 



s 2 



