104 REPORT— 1886. 



Amagat, on the other hand, finds the deviations from Boyle's law 

 at low pressures sometimes positive, sometimes negative, and all within 

 the limits of error of observation — in other words, he does not detect 

 any deviations from Boyle's law for initial pressures under 370 mm. ; 

 any such deviations, if they occur, being unrecognisable at such small 

 pressures. 



There is, Amagat says,' no appearance of any sudden change in the 

 law of compressibility of gases at the smallest pressures to which they 

 have been submitted ; it is therefore, he says, well to continue to apply 

 Boyle's law to gases down to pressures of a few millimetres. 



As to the cause of difference between his own results and those of 

 Siljestrom and Mendeleeff he suggests that — at least for Mcudeleeff — the 

 method of experimenting was favoui'able to giving prominence to a soui'ce 

 of constant error, such as a slight defect in the barometric vacuum, 

 p. 497. 



In 1884 Krajewitsch - attacked this question of compressibility of air 

 at small pressures, from 11-64 to 0'28 mm., with the general conclusion 

 that the compressibility diminishes with increasing pressure up to 11 '64 

 mm. ; and he remarks that though his results are not accurate quantita- 

 tively, there is no doubt of the qualitative result as substantiating the 

 conclusion he draws. 



The following results of observation are given in his paper : — 



mm. 



For _p=ll-636 he finds pv=l08 



and so on down to 



p 0-281 



And he states, among other conclasions which he deduces, this, that 

 at any given temperatui'e air has a certain minimum density below which 

 it loses its elasticity, this minimum density probably increasing with fall 

 of temperature. 



Volumes of Oxygen Oas at Low Pressures (Bohr). 



Again, Bohr ^ has endeavoured to solve the question for the case of 

 oxygen ; and his conclusions agree in the main with those of Mendeleeff 

 and others, while he finds, if his results are to be relied upon, a remark- 

 able point at a certain small pressure which we will speak of after briefly 

 describing his general method of procedure. 



Without describing the apparatus in detail, it may be enough to state 

 that the tube containing a bubble or two of perfectly dry and pure oxygen 

 was arranged vertically side by side with a thoroughly dry barometer- 

 tube, very completely exhausted of air, each of these two tubes standing 

 in mercury in a separate limb of a U-tube ; and that the U-tube, by 

 means of a stop-cock at its lowest point, could be brought into communi- 



' Annales de Chimie et de Physiqite (5), 1883, xxviii. p. 499. 



' Beiblatter, 1885, ix. v. p. 315. 



3 Wiedemann's Annalen dcr Physih vnd Chemie, 1886, iii, p. 469. 



