206 Prof. C. Olszewski on the 



(I) The glass tube, plunged in liquid oxygen or air, serving 

 to liquefy hydrogen, connected with the manometer m and 

 iron cylinders n n\ containing hydrogen under a pressure of 

 150 atm. 



(o) Iron flask containing hydrogen under the pressure of 

 several atmospheres, which passes through the liquid oxygen 

 in the vessel k, when its pressure is diminished. 



(pj/) Mercury manometers, serving to measure the pressure 

 of ethylene and liquid oxygen, contained in the vessels b 

 and k. 



(ri J ) Cocks serving to connect the vessels b and k with the 

 large pump. 



(s) Iron cylinder, containing liquid carbon dioxide. 



As my experiments on the liquefaction of hydrogen do 

 not at all confirm those of M. Pictet, made at Geneva in 

 1879, I requested Dr. Krzyzanowski to examine whether 

 the glaring discrepancies between my experiments and M. 

 Pictet's might not be explained by impurities contained in 

 the hydrogen he used. And indeed Dr. Krzyzanowski (24) 

 proved that, if potassium formate be heated with potassium 

 hydroxide, hydrogen cannot be obtained free from moisture, 

 even in the most advantageous case, which occurs when the 

 latter is in excess ; and that if these substances are employed 

 in the proportion given by M. Pictet, that is with potassium 

 formate in excess of what is required by the calculation of 

 molecular weights, we get by heating them a sample of 

 hydrogen containing not only water but also considerable 

 quantities of carbon monoxide and dioxide. Now these sub- 

 stances, interfering with the purity of the hydrogen experi- 

 mented on by M. Pictet, were doubtless the ground of the 

 extraordinary results M. Pictet described, and which, though 

 glaringly improbable, are cited in nearly all chemical manuals. 

 Perhaps this remark of mine will contribute to a proper 

 appreciation of M. Pictet's experiments respecting the lique- 

 faction and solidification of hydrogen; perhaps it will suggest 

 to the author (who has now established a laboratory in Berlin 

 with the special purpose of obtaining very low temperatures) 

 that he might, with advantage for science, control and rectify 

 the results of the work he performed in 1879. 



On the Optic Properties of Liquid Oxygen. 



[These investigations were made in collaboration with my friend 

 Prof. Witkowski, and were published in the Reports of the Cracow 

 Academy and in the Bulletin International, October 1891 and June 1894.] 



As far back as 1887 I discovered a very remarkable and 

 powerful selective absorption of light in the liquefied oxygen. 



