14 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 54 



The investigation of Erdmann and Marchand ' followed closely after 

 that of Dumas. The method of procedure was essentially that of the 

 latter chemist, differing from it only in points of detail. The hydrogen 

 used was prepared from zinc and sulphuric acid, and the zinc, which 

 contained traces of carbon, was proved to be free from arsenic and sul- 

 phur. The copper oxide was made partly from copper turnings and 

 partly by the ignition of the nitrate. The results obtained are given in 

 two series, in one of which the weighings were not actually made in 

 vacuo, but were, nevertheless, reduced to a vacuum standard. In the 

 second series the copper oxide and copper were weighed in vacuo. The 

 following table contains the corrected weights of water obtained and of 

 the oxygen in it, with the value found for the ratio in a third column. 

 The weights are given in grammes. 



Wt. Water. 

 62.980 

 95.612 

 94.523 

 35.401 



First Series. 



Wt. 0. 

 55.950 

 84.924 

 84.C07 

 31.461 



Ratio. 

 15.917 

 15.891 

 15.977 

 15.970 



Mean, 15.939, ± .014 



.0036 



The effect of discussing these two series separately is somewhat start- 

 ling. It gives to the four experiments in Erdmann and Marchand's 

 second group a weight vastly greater than their other four and Dumas' 

 nineteen taken together. For so great a superiority as this there is no 

 adequate reason; and it is highly probable that it is due almost entirely 

 to fortunate coincidences, rather than to greater accuracy of work. We 

 will, therefore, treat Erdmann and Marchand's experiments as one series, 

 giving all equal weight, the mean now becoming = 15.975, db .0113. 

 If we take the sum of the eight experiments, 483.137 grammes water 

 and 429.352 grammes oxygen, and compute from these figures, then 

 = 15.966. 



' Journ. prakt. Chem., 26, 461. 1842. 



