SCIENTIFIC SUilMAEY. 
527 
a channel, and supplied in a regular manner to a close chamber, into which 
the molten iron is run from the cupola. This regulated supply of the zinc 
ore is effected by means of a rotating screw, which forces the pulverized ore 
forward into the molten metal, where it becomes volatilized by reason of 
the high temperature. From the close vessel the vapours are conducted 
through a pipe to a vessel containing water, where the zinc vapours are 
condensed and the metal precepitates. The close vessel, where the zinc is 
brought into the presence of the molten metal, will after a while become 
charged with slag, which must from time to time be removed. The nitrate 
of soda is used for the purpose of rendering the slag more liquid. 
The Extraction of Silver from Lead. — An invention of a somewhat novel 
character for effectino; the extraction of silver from lead has been brought 
forward by M. Millan, of Bordeaux. The lead from which it is desired to 
extract the silver is run from the reverberatory furnace into a heating-pan, 
under which a strong fire has been made, so that no cooling of the lead may 
take place, but that its temperature may become raised after a short time. The 
surface of the lead is then skijnmed, after which the inventor introduces 
about one part, by weight, of carbonate of ammonia to every 100,000 parts, 
by weight, of lead contained in the heating-pan ; the carbonate of ammonia 
is introduced by means of a covered ladle perforated with small holes. This 
instrument, with the carbonate of ammonia therein, is stirred about in the 
lead for the space of five minutes, and is then re-inserted charged with one 
part of sea-salt to 10,000 parts of lead. This is stirred in for ten minutes, 
the quantity of sea-salt being increased when the quantity of silver contained 
is high. The skimmings are placed in heaps and afterwards heated in a 
close retort. One per cent, of zinc is then added in the same manner as the 
carbonate of ammonia and sea-salt, the mass being stirred for five minutes 
after each charge of zinc, until sufficient zinc has been introduced. The fire 
is then withdrawn that the mass may cool as quickly as possible. As soon 
as the surface is slightly crystallized, it is skimmed and retorted with the 
other skimmings, the silver being separated by distillation. 
Soiv to Detect Chromium in Iron, Steel, &c. — The following simple process 
for the detection of this metal in iron, steel, cast-iron, and ores has been 
given by M. A. Terreil in a late number of the Bulletin de la Societe Chimique. 
Treat the metal or ore by the ordinary processes to separate the silica, and 
obtain a liquid containing all the metals in solution, and in which the iron 
is at its maximum of oxidation ; then j)recipitate the liquid by an excess of a 
very concentrated solution of potass. Next pour, drop by drop, into the 
solution containing the precipitate, and heated to 80° or 90°, a very diluted 
solution of permanganate of potass until the permanganate loses its colour ; 
the reaction is terminated when the liquid takes a greenish tinge, owing to 
thenianganatc of potash, which supplies no oxygen. Then filter, saturate the 
filterized liquid with acetic acid, which immediately reduces the small quantity 
of manganate of potass that gave the solution its green colour. Next pour 
acetate of lead into the solution which finally achieves the object desired by 
throwing do’wn the chromium as a yellow chromate of lead. This process is 
equally applicable to the discovery of tungsten, vanadium, and molyldenum. 
Galiberfs Bespirator. — This apparatus, which is intended to be employed 
by miners, well-sinkers, and sewer-workers lias been lately tested, and shown 
