and Laboratory Methods. 1373 



MICRO-CHEMICAL ANALYSIS. 



XV. 



Magnesium Group — ,G1, Mg, Zn, Cd. 



GLUCINUM. 



This element, doubtless, should not be included in the present series of 

 articles introductory to the methods of micro-chemical analysis, since it is rare 

 that the analyst is called upon to search for it. 



The element glucinum being, however, of much interest from the standpoint 

 of pure chemistry, the writer has not been able to resist the temptation to include 

 it among the few elements to be considered. 



Glucinum resembles members of Group I in the crystallizing power of its 

 chlorplatinate, this salt being analogous to that of sodium as regards its solubility 

 and general appearance, but differs from the latter in that it crystallizes with 

 more water of crystallization and in the tetragonal system. 



Glucinum resembles aluminum and other trivalent metals in the gelatinous 

 character of its hydroxide precipitated by ammonium hydroxide, but differs from 

 them in that this hydroxide is soluble in solutions of ammonium carbonate. 



Like magnesium, its salts unite to form double salts with ammonium ; and its 

 chloride, when evaporated to dryness from aqueous solution, is decomposed. 



Like zinc, it is soluble in sodium or potassium hydroxide, the compound 

 formed being a glucinate of the formula Gl(OM)o. 



It has already been seen that glucinum can replace magnesium, zinc, or 

 cadmium in the triple acetate of sodium, magnesium, and uranyl. 



It is thus obvious that in the progress of a micro-chemical analysis, glucinum, 

 if present, may appear when testing for Group I, Group II, and, perhaps. 

 Group III. 



There are only three reagents which can be considered as giving satisfactory 

 crystals for the micro-chemical detection of glucinum. These are : 

 I. Chlorplatinic Acid. 

 II. Normal Potassium Oxalate. 

 III. Uranyl Acetate and Sodium Acetate. 



Of the three, the best undoubtedly is normal potassium oxalate. The other 

 two are subject to too many disturbing conditions and sources of error. 



/. Glucinum unites with Chlorplatinic Acid to form Glucinum Chlorplatinate. 



GISO^ + H2PtCl6 = GlPtClg . 8H2O + H2SO4. 

 Method. — Evaporate to dryness a drop or two of the solution to be tested, so 

 as to obtain a thin, uniform film of residue. Place a drop of the reagent next to 

 the dry residue, and carefully draw it across the latter. If the glucinum is 

 present in considerable amount, there will appear neat, transparent, square, and 

 rectangular plates and prisms of a faint yellow color (Fig, 64). 



