METALS. 



501 



placed in the same soups, sauces, sour salads, 

 etc., and exposed alike to hot, acid, and alka- 

 line solutions, and subjected to similar meth- 

 ods of cleaning. The aluminium turned to a 

 dead bluish-gray color, and lost its lustre ; the 

 German silver changed to a grayish-yellow; 

 the silver lost only in color, retaining its lustre. 

 Weighed at the end of the year, the .silver 

 spoon had lost 0.403 per cent., the aluminium 

 spoon 0.630 per cent., and the German-silver 

 spoon 1.006 per cent. For small coins, Dr. 

 Winkler thinks that aluminium is to be pre- 

 ferred to either nickel or silver alloys. 



Nickeliferow Iron Ores of Brazil. An anal- 

 ysis of some native iron from Brazil, made by 

 M. Damour, shows an extraordinarily high 

 proportion of nickel, namely 38 per cent., or 

 considerably above the ordinary proportion in 

 meteoric iron. The metal, which has a very 

 fine grain, and a lustre like that of steel, exhib- 

 its the so-called Widmanstattian figures when 

 its polished surface is acted on by an acid. 

 Strange to say, it resists for an indefinite length 

 of time the combined action of air and water, 

 without showing the least sign of oxidation. 

 The results of Damour's experiments with this 

 iron having been laid before the Paris Acade- 

 my of Sciences, Boussingault remarked that, 

 according to Berzelius, meteoric iron is not 

 oxidizable by moist air. He also called atten- 

 tion to certain experiments he had himself 

 formerly made with a view to render iron un- 

 oxidizable by incorporating with it nickel. 

 Having added successively 5, 10, and 15 per 

 cent, of nickel, he very unexpectedly found 

 that the alloy was more oxidizable than pure 

 iron. But if 38 per cent, of nickel the pro- 



Sortion found in the iron from Brazil be ad- 

 ed, the alloy is absolutely unoxidizable. M. 

 Stanislas Meunier hereupon observes that if 

 Berzelius's proposition be true then Boussin- 

 gault's explanation is insufficient, for in mete- 

 oric irons the nickel is in the proportion of 

 only 8 per cent., and of course they should be 

 very oxidizable. Some specimens of the Bra- 

 zil iron were presented to the Academy by M. 

 Daubr6e. They are of interest, owing to the 

 intrusion of magnetic pyrites, or pyrrhotine, 

 which they present. These specimens were 

 broken off from great masses of the iron found 

 in the province of Santa Catarina. The iron 

 appears to be of terrestrial origin. 



The Melting-points of Metals. The follow- 

 ing method of determining the melting-point 

 of metals, and other good conductors of heat, 

 is offered in Poggendorff^s Annalen, by Dr. 

 Hirnly: First a U-shaped tube, with arms about 

 10 centimetres long, is required, the glass of 

 which, for the sake of durability, should not 

 be too thin. The arms should be parallel and 

 close to each other. The bore of the tube 

 should not be much larger than the bulb of 

 the thermometer employed. The metal or 

 alloy to be experimented upon is to be cast in 

 the form of small bars, about the same thick- 

 ness as the bulb of the thermometer. Besides 



this, an iron bowl or crucible is wanted, which 

 can be slowly heated by means of a spirit-lamp 

 or a gas-burner. The thermometer itself is 

 made with a thin ogival bulb, which latter is 

 chemically coated with silver. As the silver 

 coating is very easily damaged, it is well to 

 strengthen it with a coating of copper in the 

 ordinary way, by means of a weak galvanic 

 current and a solution of sulphate of copper. 

 Before this, however, a fine annealed copper 

 wire .is to be wound round the thermometer 

 tube a little above the bulb. The wire is then 

 to be laid along the side of the thermometer 

 tube and fastened to it by an India-rubber band, 

 to avoid all jerks on the wire, as the latter is 

 afterward to be connected with a galvanic 

 cell. The coating of copper is allowed to ex- 

 tend above the point where the wire is at- 

 tached, by which means a better metallic con- 

 tact is insured. For the determination of the 

 melting-points of metals, or alloys and good 

 conductors of electricity, the copper coating 

 may be somewhat thicker for the sake of dura- 

 bility, while in the case of investigations with 

 non-conductors, the copper coating should be 

 thin, or may be dispensed with altogether. 



According to the height of the melting-point 

 to be determined, the crucible is to be filled 

 with mercury or some fusible alloy. To carry 

 out the experiment, the thermometer with its 

 attached wire is to be placed in one arm of the 

 U-tube, and the small bar of metal to be tested 

 in the other. The bar should be pushed in 

 quite up to the bend, so that the bar and the 

 bulb of the thermometer are as near together 

 as possible without touching. A conducting 

 wire reaching down to the bend of the tube is 

 placed by the side of the metal bar, the wire 

 being of such a length as to admit of being 

 conveniently connected with a galvanic ele- 

 ment. The whole arrangement with the U- 

 tube is attached to a convenient support with 

 clamp, so that the U-tube can be immersed in 

 the bath of mercury or melted alloy. An elec- 

 tric bell (with galvanic element) is inserted in 

 the circuit between the two wires attached to 

 the thermometer bulb and metal bar respect- 

 ively. The complete circuit is therefore only 

 broken at the bend of the U-tube, and as long 

 as this interruption lasts the bell is silent. 

 When, however, the heating of the metallic 

 bath in which the U-tube is immersed has gone 

 so far that the metal bar in the tube melts, 

 then the melted metal closes the electric cir- 

 cuit. At the same instant the bell rings, and 

 the reading of the thermometer is taken. When 

 it is considered that the thermometer and the 

 metal bar are exposed under perfectly similar 

 conditions to the source of heat, the accuracy 

 of the melting-point thus determined must be 

 self-evident. This method of experimenting is 

 of course applicable only to substances which 

 are conductors of electricity, and whose melt- 

 ing-points are such as to permit the nse of a 

 mercurial thermometer. This principle would 

 also be applicable to metals with high melting- 



