DETECTION OF THE BASIC ELEMENTS. 137 



basic elements, the insoluble substance was com- 

 posed, at least in part, of plumbic or baric sul- 

 phate ; if lead or barium is not found, but calcium 

 is, then the insoluble substance consisted, at least 

 partly, of calcic sulphate, wliich requires considera- 

 ble water or dilute acid for its complete solution ; 

 if no sulphuric acid is found, the insoluble sub- 

 stance contained only silica or silicates, besides, 

 possibly, a fluoride and carbon. 



Mix the acid solution, filtered from the silica as 

 above, and the remainder of the aqueous extract 

 together, and without filtering out any precipitate 

 that may be formed, proceed with the analysis as 

 in 3, if it is desired to analyze this solution sepa- 

 rately, in order to ascertain the composition of the 

 insoluble part of the substance ; but it will not be 

 found, in any case, to contain arsenic or ammoni- 

 um, nor will copper or zinc be likely to be found 

 in it, and not in any case unless it contained silica ) 

 lead and barium may be present as sulphates, and 

 the latter possibly as a silicate. 

 Potassium and sodium cannot, of course, be tested 

 for in this solution ; if it is desired to examine the 

 insoluble substance with respect to the presence of 

 these metals, the silicate must be attacked with 

 hydrofluoric acid or a fluoride, in the manner di- 

 rected for the quantitative analysis of silicates. 

 (§ 58, c.) 



If it is not necessary to analyze this solution sepa- 

 rately, it may be mixed at once with the first solu- 

 tion^ reserving, however, a portion of this latter 

 for the examination for the alkaline metals. - - 3 

 3. Heat a portion of the nearly neutral, first solution 

 to boiling, add to it about its volume of alcohol, 

 or twice its volume if the solution is very dilute, 



