MICROCHEMICAL REACTIONS OF THE COMMON ELEMENTS 319 



Orthorhombic. Mercuric bromide ; mercuric chlo- 

 ride; yellow mercuric iodide. 

 Monoclinic. Mercurous and mercuric nitrates. 

 Tridinic. 



DETECTION. 





 A. As Metallic Mercury by Sublimation. 



Heat upon a piece of platinum foil or upon a glass slide a 

 little anhydrous sodium carbonate until all the moisture it con- 

 tains has been expelled, cool, powder and mix a very small 

 amount with a little of the material to be examined transfer 

 to a small tube of hard glass not over 2 millimeters in internal 

 diameter, thin-walled and sealed at one end. Jar the mixture 

 down so as to obtain clean walls. Heat gently over the flame 

 of a Bunsen burner turned down to a flame i centimeter high. 

 The mercury compound will be decomposed and tiny globules of 

 metallic mercury will condense upon the walls of the tube. 

 Examine under the microscope. With a stiff hair or glass rod 

 drawn down to a hair gently rub the ring of sublimate. Examine 

 again. The mercury will have united into larger globules. 



Introduce into the tube two or three small fragments of iodine. 

 Then insert the open end of the tube into a piece of cork; warm 

 the iodine very gently and set the tube aside for a few minutes. 

 Yellow and red mercuric iodide will be formed. Warming again 

 will hasten the reaction and cause the sublimation of some of the 

 mercuric iodide. Rectangular and rhombic plates and dendritic 

 masses of both the vermilion colored iodide and the yellow 

 modification will be obtained. 



No other known element gives a reaction even remotely re- 

 sembling this one. 



From large volumes of liquid the mercury may be removed by 

 acidifying with hydrochloric acid and dropping in a steel needle 

 around which has been wound a tiny spiral of thin gold foil. The 

 deposited mercury amalgamates with the gold. The electrolytic 

 couple is lifted out after some time, washed, the gold foil removed, 

 dried, placed in a subliming tube and the mercury expelled by 

 heating. The sublimate is then characterized as above. 



