16 ATOMIC WEIGHT DETERMINATIONS. 



C. Marignac : 137.1G (O = 16). 



Three experiments were made on the titration of air-dried 

 barium chloride in crystals by Pelouze's method, {pide. supra.) 

 Five grammes of the salt required for precipitation (1) 

 4.4205; (2) 4.4195; (3)4.4210 grammes silver. Three ex- 

 periments were made on the conversion of the same barium 

 chloride into sulphate. Ten grammes of the salt gave (1) 

 9.543; (2) 9.544; (3) 9.542 grammes sulphate. In each of 

 the latter experiments the water was determined, and was 

 found to vary no more than 0.0005 grammes. Comparison 

 of the two series gives for Ag = 108, S = 16, and O = 

 8; barium equal to (1) 68.57; (2)68.61; (3) 68.55; in mean 

 68.58, or one-half of 137.16. This result is independent of 

 the possible trace of water the chloride might have con- 

 tained. In another series of three experiments the water 

 was driven off at a low red heat and determined, and the 

 salt analyzed by Pelouze's method. It was proved that 

 barium cliloride is not decomposed at the temperature em- 

 ployed. (1) gave 68.61 ; (2) 58.59; and (3) 68.55, or a mean 

 of 68.583. The salt for the experiments marked (1) was 

 prepared by recrystallization and precipitation with alcohol ; 

 that for (2) by a repetition of the same process, and for 

 (3) by resolution of (2) and precipitation with chlorhydric 

 acid gas. Marignac proved that the precipitated argentic 

 chloride contained entirely insignificant traces of barium 

 salt. CI =- 35.5. {Bibl. Univ., Archives des Sciences, Nouv. 

 Serie., 1, 1858, 209.) 



J. Dumas : 137 (0 = 16). 



Determined by fifteen experiments on the titration of 

 barium chloride with argentic nitrate, which give a general 

 average of 68.516 with an extreme difference of 0.11. The 

 barium chloride was prepared from pure nitrate and pure 

 carbonate, and from commercially pure chloride after it had 

 been freed from lead by precipitation with barium sulphide. 

 The chloride was precipitated from solution by chlorliydric 

 acid gas and melted in a current of chlorine to prevent oxi- 

 dation. Ag = 108 ; CI = 35.5. {Annates de Chimie et de 

 Physique, (3,) 65, 1859, 137.) 



BERYLLIUM. 



The atomic heat of beryllium has been determined by J. 

 Emerson-Reynolds by direct comparison with that of silver. 



