218 
POPULAR SCIENCE REVIEW. 
South Greenland, and are probably the result of the decomposition of cryo- 
lite. — Vide Chemical NewSy January 3. 
The Amount of Gold in the World. — The entire amount of gold in the 
world at the present time is estimated at about ^5,950,000,000 in value. If 
melted together it would make a lump of 660 cubic yards. If beaten out 
into gold-leaf it would cover an area of about ten thousand square miles, a 
tract one hundred miles square, less than the extent of Vermont, and little 
more than a fifth of either New York or Pennsylvania. — Halifax Mining 
Gazette^ February, 1868. 
How to Coat Iron with Copper. — Our contemporary the Illustrated London 
News gives from week to week a resume of the progTess made in scientific 
discovery, and this is done with so much ability and discrimination that we 
do not scruple to quote from its pages the following statement in reference 
to the process above referred to : The surfaces, after having been well 
cleaned with a brush and with diluted muriatic acid, are steeped in water 
slightly acidulated. The articles are then placed in a bath composed of 25 
grammes of oxide of copper, 176 grammes of muriatic acid, half a litre of 
alcohol, and quarter of a litre of water. The copper is equably deposited 
over the surfaces, the alcohol reducing the rapidity of deposition, and thus 
giving greater density to the copper film. These coppered objects may be 
zinced by placing them in a bath composed of 10 grammes of chloride of 
iron and one litre and a half of alcohol, and in contact with pieces of metallic 
zinc. A coating of antimony may be given to the coppered objects by mix- 
ing chloride of antimony with alcohol and adding muriatic acid until the 
mixture becomes clear. In this bath the obj ects may be left for three 
quarters of an hour. For silvering glass or vases four solutions are prepared, 
the first composed of 10 grammes of nitrate of silver in 100 grammes of 
water ; the second, an aqueous solution of ammonia of 0-984 density ; the 
third of 20 grammes of caustic soda in 500 grammes of water, and the fourth 
of 25 grammes of sugar in 200 grammes of water, to which is added a cubic 
centimetre of nitric acid and 50 centimetres of alcohol. Mix the three first 
solutions and then add the last, when the deposition of silver will take place. 
Hungarian Minerals. — At a late meeting of the Academy of Science of 
Vienna, Herr M. G. Tschermak gave some details of certain minerals col- 
lected in the mines of Joachimstal in Bohemia, and Kremnitz in Hungary. 
On old specimens from the former, Jie says, there may be seen decomposed 
mineral ” of monoclinic crystalline form, and associated with Haidingerite 
and Pharmacolithe. This mineral, which has a formula of 
2M9O.HO.AsO5.8HO 
is in all probability Boesslerite, become opaque through loss of water. M. 
Paulinyi has recently found at Kremnitz beautiful crystals of Voltaite 
analogous in their chemical composition to artificial crystals of this sub- 
stance obtained by M. Abich. The Kremnitz Voltaite is composed of two 
isomosptric combinations : 
4FeO.Fe2O3.7SO3.lOHO 
AlO.2Fe2O3.7SO3.lOHO 
a small quantity of oxide of iron being in the second replaced by alumina. — 
Vide H Institute March 11. 
