ATOMIC WEIGHTS 



61 



Hence C = 11.999. In two analyses, 8.6153 grammes of cinnamic acid 

 gave 23.0413 of COo. Hence 12.0015. 



SYNTHESES AND DENSITY OF HYDROCHLOEIC ACID. 



The quantitative synthesis of hydrochloric acid, with reference to the 

 atomic weight of chlorine, was first effected by Dixon and Edgar.' 

 Chlorine, prepared by the electrolysis of fused silver chloride, was weighed 

 in liquid form. Hydrogen, obtained electrolytically from barium hydrate, 

 was occluded by palladium, and so weighed. A combustion globe was 

 filled with the chlorine, and the hydrogen, ignited by a spark, was 

 burned in it. The excess of chlorine was determined by absorption in 

 potassium iodide, and subsequent titration of the liberated iodine with 

 thiosulphate solution. With corrected weights the following results 

 were obtained : 



Mean, 35.195, ± .0019 



The determinations by jSToyes and Weber ^ were differently conducted. 

 The hydrogen was weighed in palladium; but the chlorine was taken 

 in the form of potassium chloroplatinate. That salt was heated in a 

 stream of hydrogen, and the loss in weight gave the weight of chlorine 

 taken. The hydrochloric acid produced was also collected and weighed. 



Two series of experiments were made, differing in detail. In series 

 I, the hydrogen was prepared by electrolysis of sulphuric acid, and in 

 series II from barium hydroxide. The hydrochloric acid of series I was 

 collected in water directly; but in series II it was first condensed to a 

 solid by cooling with liquid air. The two series, however, were con- 

 cordant, and may therefore be treated here as one. The data obtained, 

 reduced to a vacuum basis, were as follows: 



1 Phil. Trans., 205 A, 169. 1905. 



= Joiirn. Amer. Chem. Soc, 30, 13. 190S. 



