COLLECTIONS IN KCONOMK • {;i;()L()(;v aN1» MKTALLI 1.(;v. l!)'> 



of MKiUiiij; piiio altiiiiiiiiiiiii, but iccently st'voral iiu'IIkxIs oi producing' 

 the JiH'tiil diroct from tlic oxide by eU'(;tri(t stiM-ltiii;,^ have been proposed, 

 uimI <,Mve promise ol' beiiij; siiecessfiil. 



AUoys of copper and aluiniiiiiMM are also smelted, sometiiiirs Iroin 

 corundum, by reducinjr the abiminiitm in i>r<'senee of metallic copper, 

 with which it immediately alloys. 



The collection <lonated by Col. William Frishmuth contains twelve 

 specimens, and shows several steps iu the process, toj,'ether with a full 

 series of products. 



(1) Corunauai, consist in;; of oxide of aluiiiinuiin. Nurtli C.irolina. (r>0r)96.) 



(2) .Sulphate of aliiiniiiiiiin and sodiiuii, prepared from c<iriin<luiii. (505U7.) 



(:?) Alumina, precipitated fn.m tli.' .sulphate of aluminium ami sodium. (r)Or,C>H.) 

 (4) Douhlechloridoof aluminium ami sodium, made from the precipitated auhy- 

 drou.s alumina. (r)Or>iKt.) 



(.')) Metallic aluminium, in globules, first smelting. (r)0(;0U.) 



(6) Ingot and sheet. (50601.) 



(7) Wire. (.^0602.) 



(8) Foil. (50(303.) 



(9) Hronze powder. (.5060-1.) 

 (Ill) Soldered, (noeo."). ) 



(11) Alloyed with copper, known as aluminium gold. (50ti06.) 



(12) Sheet brass and copper wire ; electroplated with aluminium. (.50607.) 



(1) Ingot, smelted from alumina dis.solved in a heated bath of tlourides and sub- 

 jected to the action of a i)owerful electric current, by the Hall process. (51620.) 



(2) Sheet metal, rolled from ingot No. 51.62!t, 0.0005 of an incli tliick. (51(;;{0.) 

 (:3) Alloy ofaluminium and copper, containing42 percent, aluminium, smelted from 



alumina by a powerful electric current in the presence of copper, by the Heroult pro- 

 cess. (516;51.) 



CHROMIUM. 



Chromum Mineral and Ore. 



curomite. 



Composition : FeOCr.O,. Proto.xide of iron and sescpiioxide of chro- 

 mium, containiufx iron protoxide 32 per cent, and chromium sesquioxide 

 OS per cent. Magnesia p:enerally replaces some of the protoxide of iron 

 and alumina the se,s(piioxide of chromium. Besides iron is fiecpiently 

 present as sesquioxide and chromium as protoxide. 



It crystallizes iu the isometric system, showinir octahedrons, but gen- 

 erally occurs line granular or massive. Its hardness is -,.5 and specific 

 gravity 4,;3lil. It is black and has a submetallic luster. Sometimes it 

 is magnet i«!, 



Chromite geiu'ially occurs hi ..r with serjicntine. It is used mainly 

 tor the manufacture of chromates for painting, dyeing, and the like. 

 Small amounts are used to produce chromium steel. Chromite occurs 

 only sparingly in nature, and the collection illu.strates the principal 

 Cnited States localities. 



(1) Very fine granular, with streaks of deeompoHitioii piodu. ts. Wood's .Mine, Lan- 

 <{i.ster County, I'eiin.sylvania. (lltWl.) 



(2) CrystHlline sand, with line sharp crystals. Lancaster County. I'ennsylvania. 



