EXAMINATION OF THE URINE. 127 



VIII. Detection of Mercury. 



Method of Furbringer. Add to 500 cc. of urine 1 to 2 cc. 

 of mercuric chloride solution (0.1 per cent.) and 10 cc. of 

 hydrochloric acid. Heat to 60-80 and digest for about a 

 quarter of an hour with 0.25 to 0.5 g. of very fine brass shav- 

 ings, pour off the urine, rinse the brass shavings repeatedly 

 with warm water, then with alcohol, and finally two or three 

 times with ether. Then place the brass shavings, twisted 

 into a roll, in a glass tube closed at one end, about 10 cm. long 

 and 8 mm. wide, and draw out the tube at some distance from 

 the brass shavings to a fine point. Heat the brass shavings 

 gently from the bottom upwards: a sublimate forms which 

 should be driven up to the capillary. This sublimate is by 

 no means all mercury, but contains zinc oxide, and some- 

 times drops of water also condense. To detect the mercury 

 it must be converted into the iodide. This is best done in 

 the following manner: Cut off the under part of the tube, 

 thus removing the roll of brass shavings, place in the upper 

 part of the tube a grain of iodine, convert this into vapor by 

 gently arming, and blow, with the aid of a glass tube, gently 

 into the upper opening of the tube. The iodine vapor is thus 

 forced over the mercury and changes this into mercuric 

 iodide. Instead of this some iodine may be placed in the 

 under part of the tube, which is then fused together and the 

 iodine volatilized by heating gently. Examine the tube with 

 a magnifying-glass or under the microscope: especially char- 

 acteristic is the conversion of the yellow mercuric iodide, if 

 it is present, into the red variety by touching it with a plati- 

 num wire, as well as the volatility of the mercuric iodide and 

 its crystal form. 



