( 222 ) 



carbonic acid was kept, a (race of oil had been left which had 

 diffused in the carbonic acid. When we thought that the whole 

 apparatus had been sufficiently cleaned by blowing pure carbonic 

 acid through it, we found : 



which by the side of Series I and II gives at the same time an idea 

 with what degree of approximation equilibrium of pressure is reached 

 by the repeated opening of the cock. Repeating the last determination 

 after continued blowing we found : 



6 -f 6 times 4 sec. | 0.426 | 0.496 | 1.19 



The last observation harmonizes pretty well with Series 1 N°. 2, 

 of which it is a repetition, the same deflections of the galvanometer 

 being moreover found. It leads to the same q'i/q b . 



It appears how misleading even the presence of slight impurities 

 may be, and that in Comm. N°. 68 the leather packings have been 

 justly called a fundamental defect of de Heen's apparatus (cf. 1 $2 

 above). 



§ 5 Correction for gravity and for slight admixtures in the ex- 

 periment of de Heen. Result. 



In order to be able to calculate the correction which is to be ap- 

 plied to {i'i/qo for gravity, we must know the density as function of 

 the level in a column of pure CO a . The accurate shape of the iso- 

 therms in the critical state being very uncertain '), this function is 

 not accurately known. Gouy has taken Sarrau's equation of state as 

 basis for his calculation. We have started from the equation of 

 state Vs. 1 of Comm. N°. 74. Only 0,0002 was found for the 

 correction at 34° and 8 c.M. difference of level, so that it may be 

 neglected. As to the correction for the admixtures for the CO,, when 

 we put their amount as given in § 2, at 0,00027, it becomes 



') It is just to the knowledge of this shape that observations as made in § 3 

 and § 7 may contribute. 



