( 768 ) 
§ 11. The measurements. 
The oxygen was prepared by heating potassium permanganate in 
a tube which was connected by a ground joint with a purifying 
apparatus consisting of washbottles filled with water, potassium 
hydroxide solution and strong sulphuric acid respectively, and then 
of a tube containing layers of glass wool covered with phosphorous 
pentoxide. This apparatus was preliminarily filled with oxygen. The 
washbottles are of the type shown in Comm. n°. 27 fig. 3 and there 
is a short cut between the tube containing the permanganate and 
the end connected to the air-pump. In this way the purifying 
apparatus can be kept in permanent order, it only being necessary 
to recharge the tube with permanganate and to completely evacuate it. 
The whole system of purifying apparatus both for oxygen and 
hydrogen (Comm. n°. 27), the mercurypump and the connecting 
tubes for filling the piezometers or thermometers are permanently 
connected together so that they remain dry. 
The purity of the oxygen used was tested by its critical phenomena 
in a tube provided with a magnetic stirrer. The values of the 
critical constants will be considered in a later communication. 
For the reduction of the Normal volume we use 
is =—|(#) ie = 0,00368 for » = 1e 
to L\dt Jp lo 
For the reduction of the measurements at higher pressure we have 
derived aps, @p3 and the ap from which ap, is calculated, from a 
graphical representation of our measurements. The values are given 
in the following table. 
TABLE Il O, , zp Comm. n° 78. 
| Temperatures. p=20 At. | p=A0At. p= bo AL 
Up= 4p; 15 6 0.0038 0.0041 0.0043 
20.0 38 40 42 
4 d 20 é k 
ge ee) | 0— 20 0.0040 0.0043 0.0045 
oA, L\ 4 /plo 
The constants of the piezometers in QO, Series V for which the 
results are given in §§ 13 and 14 are given in the following table. 
When V, is the volume at 17° C. between the above mentioned 
mark on bz and the zero of b4, and U; the volume at the same 
temperature from this zero to the meniscus which bounds the gas, 
(see Pl. IL, Comm. 69) we have 
