ATOMIC WEIGHTS 65 



and CI = 35.4657, ±.0013. Gray and Burt, calculating with H = 1.00763 

 (Morley's value), find CI = 35.459. 



The data given by Gray and Burt for the compressibilities of oxygen 

 and hydrochloric acid are too complex to admit of detailed reproduction 

 here. The normal litre of oxygen, weighing 1.42900 grammes, gave a 

 limiting density of 1.42763 grammes. That of HCl, 1.63915 grammes, 

 gives a limiting density of 1.62698 grammes. The ratio between these 

 limiting densities is the true ratio between the molecular weights ac- 

 cording to Avogadro's law. Hence, 



^ItItgI^^ ~ ^°'- Weight HCl = 36.4687 



Hence, assuming the probable errors 0.00005 for HCl, and 0.0000028 

 for Oo, CI = 35.4609, ±.0011. 



The three values derived from Gray and Burt's determinations, now 

 give the subjoined values for the molecular weight of HCl, when H = 

 1.00779. 



By critical constants HCl = 36.4548, ± .0011 



By volumetric analysis 36.4735, ± .0033 



By compressibility measurements.... 36.4687, ± .0011 



General mean HCl = 36.4647, ± .0007 



Hence CI = 35. 4569, ±.0007. Gray and Burt, from their two methods 

 alone, find CI = 35.460. The difference between their figure and the 

 foregoing combination is only one part in 11440, which is less than the 

 actual uncertainty. 



Determinations of the density of HCl have also been made, very re- 

 cently, by Scheuer.' By simultaneous weighings of the gas in six globes, 

 28 values were obtained for the weio-ht of the normal litre, as follows: 



Mean of all, as one series, 1.63941, ±.000031. 



Eeducing with the critical constants, as given by Guye and Ter 

 Gazariau, CI = 35.4538, ±.0007. 



^ Compt. Rend., 149, 599. 1909. Scheuer's complete memoir (Zeitseh. phys. Chem., 68, 575) was 

 received after this work had gone to the printer. In it he discusses his own measurements, in 

 connection with those of Gray and Burt, and finally concludes that CI = 35.466. 



