471 



60 atmospheres and the measurements of the preceding paper going 

 up to 90 aliiiosplieres liad not been able to refute it, althougii they 

 tended to show, that the polynome of three terms by wliich 

 Schalkwuk's pi\\ liad been represented using least squares did not 

 hold accurately at the higher pressures. The agreement of J in 1000, 

 with Ama(;at now obtained justifies the expectation that a deter- 

 niinafioii of the isothermal of 0^ C. at 100 atmospheres made with 

 the degiee of accuracy which we have now reached, will completely 

 confirm Amagat's direct observation at this point. Our resulrs are 

 thus well qualified to confirm the high value of Amagat's excellent 

 work. 



It appears that in the series 



Ba Ca ^ Da 



^A *vl ^A 



Da 



the term ^ — - may be neglected. The value of i>,i which follows 



fioiii our results is in good agreement with the values calculated 

 by Kamküt.ingh On.nks and Braak and by Schalkwijk from their 

 determinations of isothermals. If the various Z?.-i-vaIiies are represented 

 as a function of' tiie fempeiature, they show only small deviations 

 from the curve which may be drawn through them. The 5.i-values 

 according to Amagat are very considerably higher. 



Whereas ö.i thus agrees well with what was to be expected in 

 connection with previous observations, it is otherwise with Ca- 

 Judging by the C^-values of Kamekijngh Onnes and Braak at low 

 temperatures and those according to Amagat at ordinary and higher 

 temperatures, at 20° a value of ('a of about 0,6 >: 10-'' would be 

 expected, whereas we find a value of Ca which is more than twice 

 as high. It is less astonishing, that Schalkwijk's Ca viz. 0,993 ; 10—'' is 

 also considerably higher than what had to be expected, because at 

 the highest density reached by him the value of the term CacIa' is 

 no more than about 0,003, so that only a very small accuracy 

 could be expected here; in our observations on the other hand the 

 terra 6'.i(/.i^ rises at the highest density to nearly l°/„ of pvA, so 

 that the accuracy, although still only small, might be expected to 

 be many times higher. 



We have in vain looked for errors in our observations, which 

 might account for this unexpectedly high value of 6.i. As mentioned 

 above the observations were somewhat imjierfect as regards the 

 normal volume, for the rest they left nothing to be desired. Neither 

 could the supposition of a small error having crept in the calibration 



