302 



METALLURGY. (MISCELLANEOUS.) 



t hus maintaining a continuous circulation. This 

 not only keeps the negative pipes perfectly bright 

 and active, rendering the apparatus the best nie- 

 rhanical amalgamators, but is the essential con- 

 dition which effects the precipitation of the gold 

 in such a form that it can not be scoured off by 

 the attrition of the moving ore. By means of this 

 apparatus the gold, whether in coarse particles or 

 fine, is recovered in one operation, no filter presses 

 are required, no precipitation by zinc is neces- 

 sary, and the bullion commands a high price by 

 reason of its purity. 



In the agitation process for grinding slimes, as 

 carried on at Bland, New Mexico, the low-grade 

 slirnes are agitated with potassium cyanid for 

 twenty-four hours, while steam and compressed 

 air are admitted to pass into the solution through 

 a number of perforated pipes placed along the 

 bottom of the vat. A due proportion of lime 

 charged into a wire bucket suspended to reach be- 

 low the surface of the solution neutralizes any 

 acid reaction of the pulp, and aids later in settling 

 the slimes. After treatment the pulp is run from 

 the agitating tanks into wire settling tanks placed 

 in series, from which the overflow is made to 

 pass through upw r ard filtering tanks before it 

 goes to the zinc boxes. From the settling tanks 

 the slimes are sluiced out into decanting tanks 

 and allowed to settle for from twelve to twenty- 

 four hours. The other solutions, draw r n off 

 through openings in the side, are mixed with the 

 liquors from the wire settling tanks before they 

 pass through the filtering tanks. 



Pyritic smelting is defined by H. Long as a mat- 

 ting blast-furnace smelting process, in which 

 parts of the metallic sulfid are oxidized, thereby 

 giving a more concentrated product. The degree 

 of concentration depends mainly on the propor- 

 tion of silica in the charges. As the silica in- 

 creases, the matte fall decreases, as does also the 

 smelting power, because slags, when acid, run 

 more slowly than when basic. Thus a furnace 

 with a charge rich in pyrites, run from a basic 

 slag, will give much low-grade matte, and put 

 through large quantities with little fuel. Advan- 

 tages are claimed by S. E. Bretherton for this pro- 

 cess in comparison with lead smelting in respect 

 to the high percentage of gold and silver it saves; 

 in that it permits a high degree of concentration 

 in working ores with from 1 to 2 per cent, of cop- 

 per; and in that it allows a larger per cent, of zinc 

 in the charge, as well as more silicon and silicious 

 slags. 



Miscellaneous. In his report as deputy mas- 

 ter and comptroller of the Royal Mint, Sir Wil- 

 liam C. Roberts- Austen points out that of late 

 years a change has gradually been effected in 

 the metal for striking medals which are known 

 by the general name of bronze. Until compara- 

 tively recently, such medals were invariably 

 struck in copper, which subsequently received a 

 superficial coating mainly consisting of an oxid 

 of copper, and the medal was said to be 

 " bronzed." Such a " patina " was formerly im- 

 parted to the copper medal by heating it in con- 

 tact with iron. The Japanese have long em- 

 ployed a wet method, by the aid of which a wide 

 range of shades of brown can be imparted to cop- 

 per. The solutions are used boiling, and a variety 

 of verdigris known as " Rokusho " and sulfate 

 of copper are the main constituents. The Japa- 

 nese, moreover, are very successful in imparting a 

 more or less translucent but permanent coating 

 to the copper, which in fine examples of their art 

 reveals the crystalline structure of the metal be- 

 neath the "patina." Sir W. C. Roberts- Austen 

 observes that in the years 1897-'98 more than 



28,000 medals in commemoration of the Queen's 

 jubilee were treated in this way, and the speci- 

 mens that have been preserved in the mint show 

 no diminution in the brilliancy of the tints which 

 were originally imparted to them. Many Euro- 

 pean mints are following the Paris Mint in efforts 

 to replace pure copper by copper alloyed with 

 other metals. Analyses of coins of the reigns of 

 Hadrian and Trajan show that the alloys con- 

 tained about 87 or 88 per cent, of zinc, the re- 

 mainder being made up of tin, lead, iron, and 

 silver, with traces of arsenic and antimony. The 

 author remarks that modern medallists are work- 

 ing w T ith alloys that resemble those from which 

 the coins mentioned were struck, so that the 

 medallist of to-day is returning to the ideas de- 

 veloped in ancient Rome. 



Some clearly defined idiomorphic crystals were 

 described by E. J. Stead at the meeting of the 

 Iron and Steel Institute in May as having been 

 discovered in the hearth of a blast-furnace in 

 Monmouthshire situated in a cavity of the sand- 

 stone foundation, where spiegeleisen and ferro- 

 manganese had been made. They belonged to the 

 orthorhombic system, and are described as a car- 

 bosilicid of manganese and iron. Their composi- 

 tion was: Manganese, 51.75; iron, 35.76; silicon, 

 3.C52; carbon, 3.71; oxygen, etc., 5.16. 



In a paper on the presence of calcium in high- 

 grade ferro-silicon, read at the meeting of the Iron 

 and Steel Institute, Mr. G. Watson Gray pointed 

 out that high-grade ferro-alloys, especially those 

 produced in the electric furnace, had of late years 

 presented many interesting points to the metal- 

 lurgical chemist, and some troublesome ones to 

 the analyst. Having recently come across ferro- 

 silicon containing calcium, and not having noticed 

 the occurrence of that element in a ferro-alloy 

 recorded before, he submitted his experiences in 

 the matter, so that the presence of calcium might 

 be noted by users, and its good or ill effects on 

 steel observed. 



Mackey's amalgam press, a piston press 

 worked by steam, air, or water, removes in a 

 better way than is possible by ordinary means 

 the surplus quicksilver from amalgam, thus en- 

 riching the amalgam and reducing the amount to 

 be retorted. 



Electrolytic deposits of chromium obtained by 

 Neumann are bright gray and lustrous, but have 

 a tendency to peel off, due to films of oxid. They 

 are hard and brittle and very pure, containing 

 only from 0.1 to 0.2 per cent, of iron, and. like 

 ordinary chromium, occur in the active and pas- 

 sive states. 



Osmium, which has the highest melting-point of 

 all the metals, has been reduced by Auer von 

 Welsbach to a filamentous condition, when its 

 qualities as a conductor were found to be such 

 that it could be applied in the place of carbon for 

 incandescent electric lamps. It can withstand 

 a higher temperature than carbon, and in practise 

 affords a higher illuminating duty and.js more 

 durable. 



A gift of $32,000 has been made by Mr. Andrew 

 Carnegie to the British Iron and Steel Institute, 

 the income of which is to be applied to the award- 

 ing annually of one or more research scholarships 

 of such value as may appear expedient to the 

 council of the institute. The object of the scheme 

 of scholarships is to enable those students who 

 have passed through a college course, and also 

 who have been trained in industrial establish- 

 ments, to conduct independent researches in the 

 metallurgy of iron and steel and allied subjects, 

 with the view of aiding its advance or its appli-> 

 cation to industry. 



