1918.] The N.Z. Journal of Science and Technology. 
153 
NOTE ON EXTRACTION OF MERCURY FROM ITS 
ORES BY SODIUM SULPHIDE. 
By Charles H. Holland, M.I.M.E. 
In the latter part of the year 1915 experiments that offer attractive 
possibilities in the way of increased metallurgical efficiency were made 
on the extraction of mercury from Puhipuhi ore by dissolving the 
cinnabar in alkaline sulphide solution, and precipitating the mercury with 
aluminium. 
The ore consists of a compact, siliceous, thin-bedded rock of sedimentary . 
origin, which has probably been indurated by the influence of the over- 
lying basalt lava, with distinct evidence of crushing to rude cubes of about 
half an inch. Pulverulent cinnabar occurs frozen to the facets of the cubes, 
and fills microscopic fractures within them. The richest ore is at the hang¬ 
ing-wall, the cinnabar-content decreasing in direct ratio to the distance 
therefrom. The ore is comparatively free from gangue-minerals; ferric 
oxide, which is abundant in and near the hanging-wall, and a hydrocarbon, 
which is noticed in considerable amount during the process of retorting, 
are detrimental to the process if present in excess. 
Briefly, the method adopted was to agitate the ore with a 4-per-cent, 
aqueous solution of sodium sulphide in the presence of 1-per-cent, sodium 
hydroxide, filter, and precipitate the double sulphide of mercury and sodium 
by means of aluminium shavings. During the cycle the mixture of the 
alkaline sulphide and hydrate is regenerated if the mercury solution is 
precipitated by a metal which does not form a sulphide in the wet way. 
Small-scale experiments in the laboratory showed that the cinnabar could 
be completely dissolved in five minutes, with the proper concentration 
cf sodium sulphide and caustic soda. After agitating the filtrate with 
aluminium filings 36 per cent, of the mercury was extracted as metal and 
58 per cent, as powder mixed with foreign matter, making a total extraction 
of 94 per cent. 
A number of tests with small lots of ore were then taken in hand. Half 
a ton of ore, analysing 2*08 per cent. Hg, was ground in a Chilian mill 
to pass a 30-mesh screen, this being as fine as could conveniently be 
done. Subsequent work demonstrated that finer crushing was desirable. 
A specially constructed leaching-tank, with filter-frame on the lines of a 
cyanide leaching-vat, was made. In the tank were placed 224 lb. of ore, 
and 16 gallons of 3-6-per-cent, solution of sodium sulphide added to the top 
of the charge. Percolation commenced three hours later. At the end of 
five days percolation ceased owing to the packing of the charge. A small 
vacuum-pump was attached, but did not materially assist matters, and as 
all the cinnabar in the charge was not in solution the test was abandoned. 
Agitation was adopted by loading a butter-churn with a charge of ore and 
solution, 1 part ore to 2 parts 4-12-per-cent. Na 2 S, and agitated for fifteen 
minutes. Samples of the charge were examined under the glass. The 
