265 



already accurately known before. Only in this way is it possible, 

 to find out, what temperature really corresponds lo llial. indicated 

 by the thermoelement placed in the furnace. For this j)ni-pose we 

 have made use of the meltiiigpoints of two compounds: A/,>SV(>3 and 

 LiBoO^; the Ll^SiOs melts at a temperature of 1195(3 M. V. on 

 our standard-elements, the second at a temperature, corresponding 

 to an E.M.F. of 7822 M.V. '). In this way we observed: 



Li2SiOz. 



LiBOz. 



Heating during a long 

 time at a temperature, 

 at which the E.M.F. of 

 element IV was: 



State of the chilled 

 system : 



Heating during a long 

 time at a temperature, 

 at which the E.M.F. of 

 element IV was: 



State of the chilled 

 system : 



All glass. 



All glass. 



All glass. 



Much glass, a few crystals 



All crystals 



All glass. 



Thus, when the furnace-element indicates 11940 

 M.V., the meltingpoint of LiSiO^ is reached; the 

 correction of the indicated temperatures at 1201° C. 

 to reduce them the nitrogenthermometer, is there- 

 fore + 16 M.V. 



All glass. 



All crystals. 



Many crystals; a 

 little glass. 



All crystals. 



All glass. 



The meltingpoint of the LiBO, is thus reached, 

 if the furnace-element indicates 7780 M.V. ; there- 

 fore the correction at 845 ' C. is : -[-42 M.V. 



From both these data for 845° C. and for 1201° C, the correction 

 for every intermediate temperature is found by intrapolation ; for a 

 temperature of e.g. 965° C, it is -f- 28 M. V.; etc. It is with this 

 number, that the just mentioned temperature (in M. V.) needs lo be 

 augmented, to be reduced to the nitrogengasthermometer-scale. 



Having in this manner determined the tera|)erature-corrections for 

 the whole quenching-system within the range of temperature- from 

 845^ to 1201° C, we have chosen as an object for these e.xperiments 



1) With the IhermoelemeiiL IV three series of experiments were made, with 

 healing-rates of 30, 40 and 60 M.V. per half minute. For Ihe litliium-metaborate 

 we found thus successively as mean values: 778G, 7778 and 7781 M.V., — which 

 gives as probable value: 7782 + 4 M.V. The correction of clement IV was +40 

 M.V. at this temperature ; the true meltingpoint thus being at 7822 M.V. = 845 C. 

 (G. Th.). 



