LIFE AND LABORS OF HENRY GUSTAVUS MAGNUS. 225 



He throws new ]i^c:lit on this subject, and shows the remarkable fact that 

 there is an immense difference in therapiditj^ of the escape of hydrogen 

 in comparison with other gases. 



He published later some interesting observations npon evaporation in 

 capillary tubes, which he found most rapid in the narrowest tubes, and 

 upon the boiling of mixed liquids. In regard to the latter, he showed, 

 as theory indicated, that this boiling takes place at the temperature when 

 the sum of the tension of the mixed vapors is just sufficient to over- 

 come the pressure of the atmosphere, consequently at a temperature a 

 little lower than the boiling-point of the more volatile liquid. He ob- 

 served that this condition is never realized when the more volatile liquid 

 is placed below the other; the mixture in that case becomes overheated 

 and commences to boil suddenly with a violent explosion. 



It was also at this period of his life, in the commencement of his 

 career as professor, that Magnus made his interesting experiments upon 

 the gases contained in the blood. This subject has since been further 

 developed, but the honor will always be his, of having materially en- 

 larged the views entertained in regard to one of the most important 

 functions of animal life. The theory of respiration most generally re- 

 ceived before his day, wasthat of Lavoisier, according to which, thecom- 

 bustiou of the blood takes place at the moment when it comes in con- 

 tact with the air in the lungs. This theory was, in fact, the only one 

 then possible, since the presence of gas in the blood, emitted by expira- 

 tion, had not been shown. Magnus found in arterial as well as venous blood 

 considerable quantities of oxygen, nitrogen, and carbonic acid. The sum 

 of these three gases was, in his experiments, equal to the eighth part of 

 the entire volume of gas. He found that in arterial blood the oxygen 

 w^as from one-third to one-half; of the carbonic acid in the venous blood 

 only one-fourth to one-fifth. From this he concluded that the oxygen 

 does not combine immediately in the lungs with the carbon of the blood, 

 but absorbed by the arterial blood it is carried into the capillar}- vessels, 

 where it is employed in the combustion of the debris of the organ- 

 isms. Carbonic acid is in this way produced, which is also absorbed 

 and transported by the venous blood, and is breathed out at once on 

 reaching the lungs. This theory is now generally adopted. 



The researches of Magnus, which perhaps more than any other tested 

 his talents for experimentation, are those upon the coefficient of the 

 dilatation of gases. It had been generally admitted that this coefficient 

 was the same for all gases, and that between 0° and 100° C. their 

 volume increased for each degree 0.375 of their volume at 0. This 

 law of Gay Lussac, confirmed by Dulong and Petit, had passed into 

 the domain of undisputed facts, when, four years after the publica- 

 tion of the works of the French savant, a Swede, Eudberg, revived the 

 investigation of this question, and found as value of the coefficient of 

 the dilatation of air 0.3G4G. It was important that a quantity so con- 

 tinually applied in physical science should be positively determined, 

 15 s 



