458 



Thaddeus Estreicher on the 



engine, at the other end v with vacuometers, so that it was 

 possible at any time to read the pressure the liquid was under. 

 Between this apparatus and the air-pump there was placed a 

 screw-cock, so that by turning it more or less it was possible 

 to regulate very precisely the pressure of the oxygen, and to 

 keep up at will and for a long time the pressure we required. 

 As Prof. Olszewski pointed out some years ago, liquid oxygen 

 can be preserved for a long time under the usual pressure* ; 

 when the vessel described is employed,, liquid oxygen may be 

 preserved for hours ; the triple air-layer and the quadruple 

 glass walls isolate it perfectly w^ell from the influence of 

 external heat. By pumping in order to lower the tempera- 

 ture, we obtain round the liquid oxygen a vacuum, by which 

 a vessel of the sort approaches the principle of the u vacuum- 

 jacketed vessels " of Prof. Dewar. Whether such a vessel is 

 in practice better than one surrounded by three layers of dry 

 air, seems to me not certain ; at all events, the deposit of 

 mercury, fixed on the walls in the vacuum to prevent the 

 action of the radiant heat, besides destroying transparency, is 

 of no use, as follows from M. Pictet's researches f . Such 

 vessels as I have described have been employed for several 

 years in Prof. Olszewski's laboratory, and have proved very 

 useful. 



I have performed three series of experiments ; several 

 (generally three) determinations of the state of the thermo- 

 meter corresponded to each pressure ; the mean temperature 

 thus determined was considered as corresponding to the 

 pressure examined. The curves traced according to these 

 data are generally in close agreement, especially in their 

 lower course ; at higher pressures there is a slight difference, 

 but never more than o, 6. 



First Series. 



No. 



Pressure. 



Temperature. 



No. 



Pressure. 



Temperature. 





niillim. 



o 





millim. 





1 



735-9 



-182-7 



6 



110 



-209-7 



2 



533-9 



-185-1 



7 



100 



-2102 



3 



433-9 



-187*1 



8 



90 



-211-4 



4 



333-9 



-189-4 



9 



80 



-211-2 



5 .. 



233-9 



-1921 









The slight disagreement between the two last determinations 



* Bullet. Intern, of the Crac. Acad. January 1891, p. 45; also Wied. 

 Ann. xlii. p. GG4. 



t Zeitschr. f. physik. Chemie, xvi. p. 417 (1895). 



