MERCURY. 
§ 889 .] 
Of special methods for the separation and detection of mercury, 
Ludwig’s 1 (or some modification thereof) is the best when organic 
matters have to be dealt with : the finely divided' solid substances are 
boiled for some hours with hydrochloric acid, strength 20 per cent. ; 
then the liquid is cooled to 60°, and potassic chlorate added in half¬ 
gramme quantities until the dark liquid becomes clear ; the liquid is 
cooled and filtered, and the substances on the filter washed with water. 
To the filtrate 5 grms. of zinc dust are added, and the liquid is violently 
shaken from time to time ; a second portion is afterwards added, and 
also vigorously shaken. After some hours the clear liquid, is separated 
from the zinc and the zinc washed, first with water, then with a little 
soda solution, and finally, again with water. The zinc is now collected 
on a glass-wool filter, treated with absolute alcohol to remove water, 
and dried by suction in a stream of air. The zinc is put in a combus¬ 
tion-tube, the tube being drawn out into a thin capillary extremity, 
and a combustion made, the mercury collecting at the capillary part. 
It is a necessary refinement, should the zinc be contaminated with a 
trace of organic matter, to pack the combustion-tube as follows :—First, 
the zinc dust on which any mercury present has been deposited, then a 
plug of asbestos ; next, some cupric oxide ; and lastly, some pure zinc 
dust. Bondzynski 2 prefers to use copper rather than zinc ; for he says 
that zinc frequently contains cadmium, which latter metal also gives 
a mirror, so that, unless the mercury is afterwards identified by turning 
it into an iodide, error may be caused. 
Mercurial poisoning has occurred in hat factories, the raw material, 
furs, being treated by a solution of mercuric nitrate: this is not always 
entirely removed in the process of manufacture. A hat in use for twelve 
months was found by Lorenzo L. Lloyd and Walter M. Gardner (J. Soc. 
Chem. Ind., 1912) to contain 0-0015 per cent, mercury. For textile 
materials generally, a portion of the latter is treated with aqua regia, a 
slight excess of zinc dust added, the mixture is distilled in superheated 
steam at a temperature of 160°, through a condenser fitted with a piece 
of copper gauze. The gauze is dried and heated in a tube drawn out 
to a capillary, so as to collect the globules into the fine portion. 
O. Schumm ( Zeit. anal. Chem., 1905) has made a number of 
experiments showing that it is not necessary to entirely destroy the 
organic matter of the organs in searching for mercury. The organs and 
tissues, finely divided, are treated with hydrochloric acid and potassic 
chlorate in a capacious flask attached to an inverted (reflux) con¬ 
denser, and then the filtered fluid submitted to electrolysis—the anode 
being platinum foil, the cathode a piece of gold foil 10 mm. broad and 
30 mm. long ; the tension should be 4 volts, and the electrolysis be 
1 Zeit. f. jphysiol. Chem., i. 495, 1882; Chem. Centr., ii. 941, 1892. 
2 Zeit. f. anal. Chem., xxxii. 302-305. 
