92 



DENSITIES OF OXYlJEN AM) lIYUROtJEN 



If wf iiKTcase tlie iiieiiu I)y uue thirty-tbousaiidtli,* we Iiave 

 1) = U.585510 t,'r. ± U.UUUUlU. 



17. DENSITY (IK KLECTKOLYTIU (i.V.S. KEUUCTIO.V oK KKSILTS. 



If, now, Boyle's law apiilied to this iiiixtuio of gases, we slioukl have, putting 



H, O, M for the three densities involved, and :,\.x ^"i" the ratio of the volumes of 



oxygen and Indrogen which combine, measured at standaid temperature and 



[)ressure, 



4- (2 -f x) II >, , O -f 2 H - 3 M 

 ^ ^ ' ' = M, whence x — — - 



3 + ^ 



M — H 



If we ma\ judge by the brief account of Ledue's exjierinients given in the Comptes 

 Rendus, this reduction was ado[)ted by liim. But the reduction takes no account 

 of the deviations of the gases from Boyle's law. We reijuire to know what w>'iil<l 

 be the ])ressure of one volume of oxygen and two volumes of hydrogen when mixed 

 and made to occupy three volumes. Until direct observations are made, we must 

 compute from observations of the volume and pressure of the separate gjises at 

 ditt'ei'ent pressures. Since such ol)servations are i-epreseiited by the equation of 

 Van der AVaals with little precision, we may only hope that a reduction founded 

 on it may temporaiily serve as an approximation. Writing capitals for oxygen and 

 small letters for hydrogen, we have 



and 



(p+^)(v-b) = c. 



i'litling till' nimriii;,! volume and ])ressure equal to unity, we get 



. + A 

 and I -|- a 



15 - A IJ ;:; C, 

 b — ab = c. 



■ See note page 28. 



