MERCURY. ERDMAXN. 95 



Hence, the conclusion above stated, remains the true 

 statement of all the actual experimental determinations. 



The only additional point established is this, that the 

 pretended weighing to the hundredth of a milligramme did 

 not add the least to the accuracy of the results obtained half 

 a century ago by weighing to the milligramme only. 



The final value Fe 55.89, given by these recent authors 

 as based upon their new data, must be thrown into the 

 waste basket with all the other fancied values of that kind. 



In conclusion we merely mention the few useless deter- 

 minations by Dumas in 1860, using ferrous and ferric chloride 

 against silver. 



In our complete alphabetical summary it will be seen 

 that the means are 70 and 90 high, with a range of 158 and 

 39 in ferrous and ferric chloride respectively. 



IV. THE ATOMIC WEIGHT OF MERCURY. ERDMANN. 



The two German Chemists, Otto Linne Erdmann and 

 Richard Felix Marchand have done most excellent chemical 

 work in atomic weight determination, in perfect accord with 

 the practice of the School of Berzelius. 



They have, together, made determinations upon which 

 we base the absolute atomic weights of mercury and of 

 sulphur. To avoid double names, we ascribe Hg to Erdmann 

 and S to Marchand. 



They made, in 1844, five admirable distillations of mercury 

 from its oxide in a current of carbonic acid gas. 



Having referred to necessary details of this admirable 

 chemical work before, pp. 61-63, we need here give the 

 weighings (reduced to vacuum) and analytical ratios only: 



Xo. Oxide. Metal. Analyt. Ratio. 



1 82.0079 75-9347 0.92 594 



2 51.0320 47- 2 538 0.92 597 



3 84.4996 78.2501 0.92 604 



4 44-6283 4 T -3 2 85 0.92 606 



5 118.4066 109.6408 0.92 597 

 Grammes. Mean 0.92 600 

 Hg : Hg O = 200 : 216 = 0.92 593. Chg. 3 high. 



