130 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



In a criticism of Scott's work, Thorpe ' has pointed out the possibility 

 of errors due to the vacuum reductions; errors discussed long ago by 

 Marignac, and recently, in more detail, by Guye and Zachariades." The 

 substances analyzed were weighed in powder, under which conditions they 

 are liable to condense and occlude air. A probable correction, applied 

 to Scott's weighings, reduced the atomic weight of carbon to 12.008, in 

 harmony with other good determinations. To this criticism Scott ^ pub- 

 lished a rejoinder, seeking to show, on the basis of experimental evi- 

 dence, that the supposed errors do not, in fact, exist. According to 

 Guye and Zachariades, the errors noted by them in the study of 26 com- 

 pounds may amount to as much as, or even more than, 3 parts in 10,000. 



Since silver tartrate and silver racemate are isomeric compounds, their 

 figures may be consolidated into one series. We then have the following 

 ratios in this group, to be discussed in connection with other ratios later: 



AgCHjOotAg: : 100: 64.6434, ±: .0007 

 Ag,C4H,Oe:2Ag: : 100: 59.2778, ± .0009 

 AgAH40,:2Ag: : 100: 62.0016, ± .0096 

 AgC,H,0,:Ag: : 100: 47.125, ± .0012 

 Ag:COo: :100:40.723, ± .0071 

 AgCN: Ag: : 100: 80.567, ± .0010 

 Ag: (aH,),NBr: :100:194.870, ± .0045 

 Ag: (CH3),NBr: : 100: 142.824, ± .0123 



THE SULPHUR RATIOS. 



The atomic weight of sulphur has been determined by means of several 

 ratios connecting it with silver, chlorine, oxygen, hydrogen, sodium and 

 carbon. Other ratios have also been measured, but they are hardly avail- 

 able here. The earlier results of Berzelius were wholly inaccurate, and 

 his later experiments upon the synthesis of lead sulphate will be used in 

 discussing the atomic weight of lead. Erdmann and Marchand deter- 

 mined the amount of calcium sulphate which could be formed from a 

 known weight of pure Iceland spar; and later they made analyses of 

 cinnabar, in order to fix the value of sulphur by reference to calcium and 

 to mercury. Their results will be applied in this discussion toward ascer- 

 taining the atomic weights of the metals just named. 



First in order let us take up the composition of silver sulphide, as 

 directly determined by Dumas, Stas and Cooke. Dumas' ■* experiments 

 were made with sulphur which had been thrice distilled and twice crystal- 

 lized from carbon disulphide. A known weight of silver was heated in 

 a tube in the vapor of the sulphur, the excess of the latter was distilled 



1 Proc. Chem. Soc, 25, 285. 

 ^Compt. Rend., 149, pp. 593 and 1122. 

 »Proc. Chem. Soc, 25, 2S6. 

 *Ann. Chem. Pharm., 113, 24. 1860. 



