266 Hillebrand and Schaller — Mercury 



this effect. of the gangue the method would be an excellent 

 one for obtaining proof as to the presence or absence of basic 

 oxygen. The nitrogen found by the third method was finally 

 tested by passing it over hot magnesium, which absorbed 

 apparently the whole of it. It was also tested spectroscopically. 

 The analytical results were as follows, calculated to gangue-free 

 substance, the modes of decomposition employed being indicated 

 at the heads of the several columns : 



Nitrogen percentages by different methods. 

 Gas-volumetric 



Av. 



Na 2 S 



HC1 



With Na 2 CO s 



Without NaoC0 3 



' NH 4 Br 



2-56 



2-57 



2-53 



2-61 



2-78 



2-57 





2-55 



2-74 



2-76 



2-55 





2-60 



2-67 



2-74 



2-55 





2-58 

 2-43 



2-86 



2-70 



2*555 







2-74 



2-54 



The single determination after solution of the mineral in 

 hydrochloric acid and removal of the mercury as sulphide and 

 of the S0 4 as the barium salt, is regarded with confidence, as 

 also those by the sodium sulphide method. The greater vari- 

 ation among the results by the gas-volumetric tests with sodium 

 carbonate is to be ascribed to the small amounts of mineral 

 used — - 25-0'5 gram, the uncertainty in the burette readings 

 in the upper section of the instrument and the greater chance 

 for loss or gain during the numerous manipulations. The high 

 results by the ammonium bromide method have been explained 

 above. Those by the gas method without sodium carbonate 

 are not clearly accounted for, but the results obtained in that 

 way were always less satisfactory by reason of the fouling of 

 the pump outlet and of the mercury in the collecting tube by 

 the free chlorine that was formed, 



(2) Mercury. Mercury was determined in several ways, 

 almost always in connection with one of the nitrogen deter- 

 minations : ( a ) As mercury by ignition with sodium carbonate 

 and once as in organic combustion of mercury compounds. 

 Most of the determinations were by this method. ( b ) As mer- 

 cury by electrolysis from sodium-sulphide solution. ( c ) As 

 the sulphide. The last method usually afforded higher and 

 probably truer results than the first. 



(3) Chlorine and sulphur. Since slight loss of chlorine and of 

 sulphur as sulphide dioxide almost always resulted when the 

 mineral was heated by itself, these components were determined 

 in the sodium carbonate employed for the gas-volumetric deter- 

 mination of nitrogen. A greater variation among the few 



