April 27, 1900.] 



SCIENCE. 



643 



1888, Wroblewski devoted his time to a 

 laborious research oa the isothermals of 

 hydrogen at low temperatures. The data 

 thus arrived at enabled him, by the use of 

 Van der Waal's formulse, to calculate the 

 critical constants, and also the boiling point 

 of liquid hydrogen. 



Olszewski returned to the subject in 1891, 

 repeating and correcting his old experi- 

 ments of 1884, which "Wroblewski had 

 failed to confirm, using now a glass tube 

 7 mm. in diameter instead of one of 2 mm. 

 as in the early trials. He says : " On repeat- 

 ing my former experiments, I had no hope 

 of obtaining a lower temperature by means 

 of any cooling agent, but I hoped that the 

 expansion of hydrogen would be more effi- 

 cacious, on account of the larger scale on 

 which the experiments were made." The 

 results of these experiments Olszewski de- 

 scribes as follows : " The phenomenon of 

 hydrogen ebullition, which was then ob- 

 served, was much moi-e marked and much 

 longei" than during my former investiga- 

 tions in the same direction. But even then 

 I could not perceive any meniscus of liquid 

 hydrogen." Further, " The reason for ivhich 

 it has not hitherto been possible to liquefy hy- 

 drogen in a static state, is that there exists no gas 

 having a density between those of hydrogen and 

 of nitrogen, and ivhich might be for instance 

 7-10 (H:=1). Such a gas could be 

 liquefied by means of liquid oxygen or air 

 as cooling agent, and be afterwards used 

 as a frigorific menstruum in the liquefac- 

 tion of hydrogen." 



Professor Olszewski, in 1895, determined 

 the temperature reached in the momentary 

 adiabatic expansion of hydrogen at low 

 temperatures, just as Wroblewski had done 

 in 1885, only he employed a platinum-re- 

 sistance thermometer instead of a thermo- 

 junction. For this purpose he used a small 

 steel bottle of 20 or 30 cc. capacity, contain- 

 ing a platinum-resistance thermometer ; 

 in this way the temperatures registered 



were regarded as those of the critical and 

 boiling points of liquid hydrogen, a sub- 

 stance which could not be seen under the 

 circumstances and was only assumed to 

 exist for a second or two during the ex- 

 pansion of the gaseous hydrogen in the 

 small steel bottle. 



The results arrived at by Wroblewski 

 and Olszewski are given in the following 

 table, and it will be shown later on that 

 Wroblewski's constants are nearest the 

 truth. 



Wroblewski, Olszewski, 

 1885. 1895. 



Critical temperature ^240° — 234° 



Boiling point —250° —243° 



Critical pressure 13 atm. 20 atm. 



The accuracy of Wroblewski's deductions 

 regarding the chief constants of liquid 

 hydrogen following from a study of the 

 isothermals of the gas is a signal triumph 

 for the theory of Van der Waals and a 

 monument to the genius of the Cracow 

 physicist. From these results we may 

 safely infer that supposing a gas is here- 

 after discovered in small quantity four 

 times more volatile than liquid hydrogen, 

 having a boiling point of about 5° absolute, 

 and therefore incapable of direct liquefac- 

 tion by the use of liquid hydrogen, yet by 

 a study of its isothermals we shall succeed 

 in fi.nding out its most important liquid 

 constants, although the isolation of the real 

 liquid may for the time be impossible. 



In a paper published in the Philosophical 

 Magazine, September, 1884, ' On the Lique- 

 faction of Oxygen and the Critical Vol- 

 umes of Fluids,' the suggestion was made 

 that the critical pressure of hydrogen was 

 wrong, and that instead of being 99 atmos- 

 pheres (as deduced by Sarrau from Am- 

 agat's isothermals) the gas had probably 

 an abnormally low value for this constant. 

 This view was substantially confirmed by 

 Wroblewski finding the critical pressure of 

 13.3 atmospheres, or about one-fourth of 

 that of oxygen. The Chemical Neivs,B&^iQVcy- 



