208 harper: thermometry lag 



itself is 0.01 calorie per ° C. These figures lead to a value of \ 

 of one-half second, for immersion in vigorously stirred water. 



Thermo-electric thermometers. — The lag of a thermocouple, like 

 that of a resistance thermometer, is almost entirely a question 

 of the form of mounting. Depending upon the way of supporting 

 and enclosing the junction, one would expect to find lags ranging 

 all the way from a fraction of a second to perhaps 30 seconds, for 

 immersion in water, and correspondingly greater values in air. 

 With the wide latitude of variation in design without impairing 

 the usefulness of the thermocouple, there have appeared almost 

 as many forms of instruments as there are makers, in conse- 

 quence of which it seemed unimportant to determine the lag of 

 any particular form. 



Thermometric lag in calorimetry. — Although the controversy con- 

 cerning the effect of thermoelectric lag on calorimetric results may 

 be said to have been settled by a recent conclusive paper pub- 

 lished by W. P. White, the widespread attention attracted to the 

 subject by the conflicting views expressed by eminent writers prior 

 to the publication of the paper cited, has made it seem worth 

 while to treat the subject rather fully in the more complete paper. 

 An analysis, differing radically from that of White, will be found 

 there, the conclusions being, however, substantially those stated 

 by him. 



