SCIENTIFIC SUMMARY. 
101 
Preparation of Indium in the Pure State. — In a recent number of Dingler’s 
Polytechnisches Journal , a paper on this subject appears by Herren Roszler 
and Wolf, and is thus abstracted in the useful weekly summary of our con- 
temporary the Chemical News. The authors make use of the Freiberg zinc 
for the purpose of obtaining indium. The zinc is dissolved in hydrochloric 
acid, and next boiled with excess of metallic zinc, whereby a spongy metallic 
precipitate is obtained of the following composition Lead, 136; tin, 0 02; 
cadmium, 0T3 ; copper, 0-004; indium, 0-15 ; together, 1-529 per cent, of the 
metallic zinc employed. This mass is first treated with sulphuric acid to 
remove the lead. The whitish- coloured mass is next treated with boiling 
water ; this solution is again treated with zinc, whereby a spongy metallic 
mass is obtained, which is acted upon by strong nitric acid, the excess of 
which is evaporated, and the oxides of tin and any remaining sulphate of 
lead are eliminated. The residue is taken up with water, to which am- 
monia is added, whereby the oxide of indium is precipitated ; and, after 
drying, this oxide is reduced to the metallic state by means of cyanide of 
potassium. 
Non-porous Castings of Copper . — It is stated that by melting copper in 
plumbago crucibles previously lined inside with pipe-clay and dried, non- 
porous castings may be obtained. As soon as copper, while in a molten 
state, is in contact with coal, or carbonaceous matter, it yields a porous and 
spongy casting. 
The quantity of Zinc obtained in 1868. — The returns obtained from the 
zinc mines of the United Kingdom show a production in the year 1868 of 
12,782 tons of zinc ores, principally sulphide of zinc (blackjack), the value 
being estimated at about 39,192/. The number of mines was 35 : 18 in 
England, 15 in Wales, 1 in Ireland, 1 in the Isle of Man. In England and 
Wales the chief production was from three counties: 3,350 tons from Den- 
bighshire, 2,858 tons from Flintshire, 2,061 tons from Cornwall. 3,278 
tons were produced in the Isle of Man. The production of metallic zinc 
was about 3,713 tons of the value of 75,436/. All these figures are lower 
than those for the preceding year, 1867. Prices were lower in 1868 than 
in 1867 in the London market, the mean price of spelter falling from 217. 6s. 
in 1867 to 20/. 6s. 4 d. in 1868, and the mean price of zinc (in sheets) from 
27/. 7s. 6d. to 25/. 13s. 4c?. per ton. 
Augite and Amphibole. — A paper relating to these will be found in the 
proceedings of the Chemical Society of Berlin, No. 13. 
Durangite is the name of a mineral from Durango in Mexico, and de- 
scribed in Silliinan’s American Journal for September. 
MICROSCOPY. 
For progress in general histology we must refer our readers to the sections 
of Geology, Botany, and Zoology. In reference to microscopic progress, we 
can do no better than state that in the three past numbers — October, 
November, and December — of the Monthly Microscopical Journal , the 
following highly important contributions will be found : — 
