( 430 ) 



Ton r. = 273°.08 K 



where K (Kelvin) sUiiids tor degrees on the altsoliite scale of which 

 100 occur between the free'/iiig- point and the boiling point of watei-. 



The data are not sufficiently accurate to allow us to determine 

 the last decimal to less than unity ') ^). Tiie value found here agrees 

 very well with that which may be derived from the most reliable 

 data of other observers ''). 



The method followed here of deriving the pressure coefiicient for 

 infinitely small densities by means of determinations of isotherms at 

 pressures between 25 and 50 atmospheres is preferable to using 

 either the data of (.happuis or those of Amagat. It is true that in 

 the former case the coefficient C may be neglected without error 

 arising, but the small difference of pressure has a bad influence on 

 the determination of B. On the contrary with higher pressures, 

 such as with Amagat's determinations, the coefficients C and the 

 higher ones have too much influence to allow an accurate derivation 

 of the value of B. In our deteiminations C is of so small account 

 that an error in the estimation of C may be neglected for the 

 determination of B ''). 



While therefore the influence of errors in 6a may be neglected 

 we find on the other hand that the pressures are so large that 

 an error in the pressure coefiicient passes diminished to about 



1) In discussing the isotherms we intend to refer to a small systematic difTe- 

 rence between the isothermals of hydrogen at 20° G. according to Comm. N'\ TU 

 (June 19Ü1) and those at 0^ G and 100^ G. of Gomm. N\ 100^. It rather points 

 at Tö° c. = 273°.07 K. 



2j We intend to tietermine this value still more accurately with nitrogen and 

 helium by means of determinations of isotherms at 0° G. and 100° G. and of 

 pressure coefficients between 0° G. and 100^ G. where we proceed according to 

 Gomm. N'\ 60 (the determination of Ho is also repeated), but as a higher degree 

 of accuracy is wanted (designated by that now readied with the determinations 

 of the isotherms) we now take a reservoir of 300 c.c. 



3) Gomp. for this the note of § 2. XIV Gomm' N'. 97^ 



*) If for instance in the adoption of Ca an error of 15'Vo has been made, wliich 

 with a view to the data of table XXII of Comm. N*^. 100^^ probably includes the 

 higher limit for the error for lower temperatures, this becomes only 0.0000001 

 which, considering tliat the greatest density which occurs in the determinations of 

 Gomm. N''. 100'^ amounts to about 50 times the normal one, would cause for 0° G. 

 an error in B\ which remains below 0.000005. As such a systematic error would 

 change tlie value of rA.iou° in nearly the same way, the error in this difference 

 will be much smaller and, for instance, the error arising thence in the difference 

 betweeu B\.i)° and iiA.ioo'' may be estimated at O.OOOOOf, i. e. V.5 of the error 

 in the absolute value of B\. Tlie error in tlie absolute zero arising from the 

 two influences combined remains below O-'.Ol G. 



