22,6 Cole: Hemmethylenetetramine 535 



According to Ray and Sarker," the cadmium iodide-hexamethy- 

 lenetetramme compound may have the formula 



2(CdL).2(HI)3(C, ; H 12 N 4 ) or 2(CdI,)2(C H 12 N 4 ). 



The following metals are grouped together because of the 

 similarity of the crystals formed with hmt and with hmt + KI: 



In hydrochloric acid solution they all yield triclinic, four- or 

 six-sided plates with hmt. A similar type of crystal is given 

 when potassium iodide is added (Plate 2, figs. 10 and 11). In 

 all cases, the crystals form only around the melting fragment 

 of hmt or potassium iodide. 



Sensitivity with hmt, 1 : 900. 

 Gold chloride solutions yield with hmt very characteristic 

 pale yellow needles or thin plates showing strong polarization 

 with parallel extinction. These needles form either a kind of 

 grid at 60° angles or rosettes of plates or needles. There is 

 sometimes a tendency to form long, curved, hairlike needles 

 (Plate 1, fig. 3). Since the crystals are soluble in excess of 

 reagent, care must be taken to use only a very tiny fragment 

 of hexamethylenetetramine in the test drop. The compound 9 

 formed has the formula C H 12 N 4 . AuCl 3 . 



Mercury and silver interfere with the test for gold. The 

 presence of palladium tends to make the gold come out as moss- 

 like crystals. Platinum, palladium, and iridium are readily dis- 

 tinguished from gold by this test (Plate 1, fig. 5). 



Sensitivity with hmt, 1 : 2,000. 



Iridium salts yield with hmt highly characteristic tiny red- 

 brown octahedra or crosses belonging to the isometric system. 



A large excess of reagent should be avoided. The crystals 

 usually appear after a few minutes near the periphery of the 

 drop and grow larger on standing. 



