in Iron Ores containing Phosphoric acid. 335 
taken for the examination. As sulphur would have been 
vaporized by the heat, the burning, of course, proved the pres- 
ence of some other body. As the absence of zinc and the 
members of the fifth and sixth groups had been proved, the 
only elements supposed to be precipitable by sulphuretted 
hydrogen under the existing conditions, the supposition was 
that a mistake had occurred. The experiment was, therefore, 
repeated and with identical results. As it now seemed certain 
that sulphuretted hydrogen had caused a precipitate, the next 
step base was to determine its character. The substance was 
white both before and after heating, and resembled closely sul- 
phide of zine. After burning, it held no sulphur. e absence 
of color and sulphur would alone have seemed sufficient proof 
of the absence of the fifth and sixth groups, without the con- 
curring evidence as afforded by the previous regular qualita- 
tive tests. But since it could not be denied that a substance 
