SEPARATION OF METALS INTO DIFFERENT GROUPS. 233 



33. SEPARATION OF METALS INTO DIFFERENT GROUPS. 



General remarks. The preliminary examination will, in most 

 cases, decide whether or not a metal or metals are present in the sub- 

 stance to be examined. If there be metals, the solution should be 

 treated according to Table II., page 236, in order to find the group 

 or groups to which these metals belong, and also to separate them 

 into these groups, the individual nature of the metals themselves 

 being afterward demonstrated by special methods. 



The simplest method of separating from each other the 55 metals 

 known, if all were in one solution, would be to add successively 55 

 different reagents, each of which should form an insoluble compound 

 with but one of the metals. By separating this insoluble compound 

 from the metals remaining in solution (by filtration), and by thus pre- 

 cipitating one metal after the other, they all could be easily separated. 

 We have, however, no such 55 reagents, and are, consequently, com- 

 pelled to precipitate a number of metals together, and the reagents 

 used for this purpose are known as group-reagents. 



They are : 



1. Hydrogen sulphide, added to the solution previously acidified by 

 hydrochloric acid. Precipitated are : the metals of the arsenic and 

 lead groups as sulphides. 



2. Ammonium sulphide, added after supersaturating with ammonium 

 hydroxide. Precipitated are : the metals of the iron group and of 

 the earths as sulphides or hydroxides. 



3. Ammonium carbonate. Precipitated are : the metals of the 

 alkaline earths as carbonates. 



4. In solution are left : the metals of the alkalies and magnesium. 

 The order in which these group-reagents are added cannot be 



should be noticed first in making a qualitative analysis ? 313. By what tests 

 may organic compounds be distinguished from inorganic compounds ? 314. 

 Explain the terms decrepitation and deflagration. 315. Mention some sub- 

 stances which are completely volatilized by heat, some which are fusible, and 

 some which are not changed by heating them. 316. What is meant by " hepar/' 

 and which element is indicated by the formation of hepar ? 317. Mention some 

 metals which may be liberated from their compounds by heating on charcoal 

 with potassium cyanide and carbonate. 318. Which metallic compounds and 

 which acids are capable of coloring a non-luminous flame ? Name the colors 

 imparted. 319. State the metals which impart characteristic colors to a borax 

 bead. 320. Which solvents are used for liquefying solids, and what precau- 

 tions should be observed in this operation ? 



