Conduction of Heat in Liquids. 41 



Table IT. 













t. 



t. 



Liquid. 





P- 



c. 



pc. 



Water 



Water not 











siphoned. 



siphoned. 





1 



•o 



10 



1-0 



9-0 



10-7 



Sulphuric acid solution .... 



1 









ft -*7^ 





Do. 



1 



1 



0-877 



0-965 



8-5 





Do. 



1 



•14 



0-843 



0-961 



8-5 





Do. 



1 



•18 



0-802 



0-946 



8-25 







1 



•276 



0-247 



315 



6-65 











849 



-675 



573 



10-75 



13-2 









•803 



0-50 



0-401 



10-25 



12 25 









•875 



0-43 



0-376 





14 -6 



In each case the density was taken with a hydrometer at or near 

 the temperature of the experiment, and the specific heats are taken 

 directly from ' Watts' Dictionary of Chemistry,' or obtained by inter- 

 polation from tables given there. In the case of the last three liquids 

 the specific heat was also obtained experimentally, as these liquids 

 vary somewhat in composition. The results so obtained were some- 

 what rough, but were sufficiently good to act as a check on the 

 values taken. Small errors in the specific heat are not of much im- 

 portance, as the probable error in the experiments on the conductivity 

 amounts to at least several per cent, of the numbers taken. Further, 

 the mean temperature to which the conductivity should be referred is' 

 also a somewhat doubtful matter. 



The introduction of small impurities in the liquids did not appre- 

 ciably alter t. For instance, small quantities of salt were put into 

 the methylated spirit, and small quantities of the latter into water 

 without producing any apparent effect. It would thus appear that 

 the absolute purity of the liquids used is not of much consequence. 

 Care was, however, taken to keep them as pure as possible, the bisul- 

 phide of carbon in particular being redistilled before use. 



In every case the value t is the mean of a good many experiments, 

 and, as a rule, the individual experiments agreed well together. Thus, 

 when the siphon was not used the values obtained for t varied from 

 10*3 to 11 for water, from 12*75 to 14 for methylated spirit, and from 

 1425 to 15 for turpentine. When the siphon was used the extreme 

 differences in the numbers obtained for t were about as large as in the 

 other method, and thus the agreement between the experiments was 

 really not quite so good. This was only to be expected, as there was 

 necessarily some slight variation in the time taken to siphon and in 

 the result of the operation. 



In obtaining a mean value for t the following method was adopted : 



