Heat of Iron at High Temperatures. 



437 



specimen at lower ranges showed that the method gave a 

 result in agreement with that obtained by the earlier method, 

 and when plotted together it is impossible to distinguish the 

 observations made with the various sized specimens in the 

 different series. Further, no systematic difference was 

 shown between the earlier sets, using a platinum thermo- 

 meter for temperature measurement, and those done later 

 with thermocouples. 



All the values of Q T obtained from the individual obser- 

 vations were plotted on a large scale, and a mean curve drawn 

 from which the results in the later tables were calculated. 





Temp. 



QoT. 



25-5 





Temp. 



Qo T - 



95-8 



1 



216 



19 



672 



2 



216 



25-3 



20 



721 



111-5 



3 



385 



494 



21 



741 



1138 



4 



386 



49-7 



22 



782 



123-6 



5 



392 



499 



23 



787 



126-6 



6 



397 



50-7 



24 



818 



133-1 



7 



466 



599 



25 



819 



133-7 



8 



489 



65-2 



26 



826 



132-4 



9 



494 



664 



27 



842 



136-4 



10 



503 



674 



28 



856 



139-6 



11 



520 



690 



29 



859 



142-6 



12 



585 



80-3 



30 



866 



1404 



13 



588 



823 



31 



896 



146-6 



14 



597 



84-7 



32 



923 



150-7 



15 



601 



85-3 



33 



1006 



1560 



16 



613 



874 



34 



1077 



161-9 



17 



636 



88-9 



35 



1111 



174-4 



18 



637 



91-0 



36 



1144 



190-0 



These show the value for Q T obtained by the author, along 

 with the original and recalculated values given by Pionchon's 

 experiments'*. It will be seen that the agreement between 

 the two latter is almost perfect up to 900° 0. In his paper 

 Pionchon mentions the fact that above this temperature the 

 experiments become very much more difficult, and that the 



* Pionchon's experimental values are quoted in Le Chatelier and 

 Boudouard's ' Mesure des temperatures elevees.' Both in the original 

 French and in the new English translation "by Burgess there are, how- 

 ever, two serious errors. 



The value for 200° should be 23-5 instead of 22-5 

 and that for 400° „ 51-5 ., 41 '5 



to the nearest - o unit. 



