466 



METALS. 



By the same process, using sesquioxide of 

 chromium in place of molybdic acid, chromium 

 was obtained possessing a sp. gr. 6.2. The 

 best results were procured by using a reducing 

 mixture of cyanide of potassium and animal 

 charcoal. 



Niobium and Tantalum. Professor St. 

 Claire Deville has presented to the French 

 Academy a paper by Marignac, giving an ac- 

 count of various attempts made by him to ob- 

 tain niobium and tantalum (metals, so called) 

 in a metallic state. These efforts, though un- 

 successful, have resulted in the discovery of 

 several new and interesting compounds. Flu- 

 oniobate of potassium is reduced without 

 difficulty by sodium in a crucible of wrought 

 iron, but the product of the action is an alloy 

 of sodium and niobium, or niobide of sodium 

 in the form of a black powder. Water decom- 

 poses this body and transforms it into a niobide 

 of hydrogen containing about 1 per cent, of 

 hydrogen, and having the formula NbH. The 

 substance obtained by Eose was certainly a 

 protoxide of niobium, Nb 2 O. The niobide of 

 hydrogen is an extremely fine black powder 

 of density 6.66. It is not attacked by chlor- 

 hydric, nitric, or dilute sulphuric acid, but 

 may be attacked and dissolved by concentrated 

 boiling sulphuric acid and by fused alkaline 

 bisulphates by boiling with caustic alkalies and 

 particularly by fluohydric acid even when 

 dilute. When heated in the air, it ignites and 

 is converted into niobic acid. The niobide of 

 hydrogen is very stable and may be ignited for 

 an hour in a current of hydrogen without 

 change, except that its density increases to 

 7.3V. Fluoniobate of potassium heated with 

 magnesium produced a violent explosion. The 

 reduction with aluminium, in a crucible of gra- 

 phite, yields a niobide of aluminium, NbAl 3 , 

 which is a highly crystalline iron-gray powder, 

 with a strong metallic lustre and with a density 

 of 4.45 to 4.52. Fluotantalate of potassium 

 yields with aluminium an alloy of similar con- 

 stitution and properties. The density of this 

 body is 7.02 ; it dissolves easily in fluohydric 

 acid. Professor Deville described two new 

 compounds of niobium obtained by himself, but 

 not analyzed. When niobate of potash is heat- 

 ed to about 1,200 degrees, with a small excess 

 of carbonate of potash, in a crucible of graphite 

 surrounded by a mixture of rutile and carbon, 

 very beautiful black cubes are obtained, which 

 are converted by chlorine into a mixture of 

 chloride and oxychloride of niobium. When 

 the calcination takes place in a crucible of 

 graphite heated to the highest possible tem- 

 perature, ' but not surrounded by rutile and 

 carbon, prismatic crystals are obtained of a 

 magnificent dark bronze color, which are doubt- 

 less the nitro-carbide of niobium analogous to 

 the well-known titanium compound analyzed 

 by Wohler. (Sci. Int. Am. Jour, of Science.} 



Aluminium Bronze. This substance is grad- 

 ually coming into use for table ware and vari- 

 ous ornamental purposes. It is extensively 



employed in the' manufacture of cheap watch- 

 cases, more nearly resembling gold than the 

 "oreide" metal, and therefore well calculated 

 to deceive the unwary. The production of 

 aluminium bronze is achieved in different ways 

 by different manufacturers. M. Evrard, one 

 of those engaged in it, does not combine cop- 

 per and aluminium directly together. He 

 makes use of a pig-iron containing a certain 

 proportion of aluminium. This is slowly heat- 

 ed to fusion, when copper is added to the 

 melted mass. Aluminium, having more affinity 

 for copper than for iron, abandons the latter 

 and unites with the copper. The entire mass, 

 having been well stirred, is then allowed to cool 

 slowly, so that the aluminium bronze, which is 

 denser than iron, may find its way to the bot- 

 tom of the crucible. The same process may 

 be employed, according to M. Evrard, to ob- 

 -tain a bronze of silicium. If silicium could be 

 separated from pig-iron, by adding a quantity 

 of copper, the process might be valuable to 

 iron manufacturers. 



It is proposed to protect the staircases of the 

 ascent of the columns in the Place Vendome. 

 Paris, by thin plates of aluminium bronze. 

 On account of the wearing away of the stairs 

 by much usage, public access to them has been 

 recently prohibited. M. Cazeau suggests the 

 use of the new bronze, having determined its 

 value for the purpose, by experimenting with 

 it on the stairs of a very busy factory. Plates 

 of bronze inch thick were as good as new 

 after eleven months of service on the factory 

 stairs, when plates of common bronze $ inch 

 thick, had worn out in six weeks. 



Magnesium. There is no important step to 

 record in the manufacture of this metal, or its 

 adaptation to new purposes, in the year 1868. 

 Its cost has precluded its employment, to any 

 great extent, as a means of supplying light. A 

 statement in the English Builder, from one 

 claiming to know, expresses the hope and be- 

 lief that magnesium, during the present year, 

 will be manufactured in England by improved 

 processes, so that it can bo retailed at a shilling 

 an ounce. 



The Effect of Cold on Metals. The Mechanics' 

 Magazine has some remarks on the effect of 

 cold on metals. The axles and springs of rail- 

 way carriages are known to be much more 

 liable to fracture during a severe winter than 

 at other times. The lead pipes which burst 

 with frost would undoubtedly bear a much 

 greater strain at a higher temperature, when 

 the metal would simply expand with the pres- 

 sure. On tin, the effect of cold is much more 

 marked. Some pigs of Banca tin,' exposed 

 during the winter at St. Petersburg, under- 

 went a most remarkable change. The metal 

 became fibrous, and deep fissures were pro- 

 duced in it in every direction. Fritsche, who 

 details the circumstances, says that the phe- 

 nomenon had been observed before in Eussia, 

 once in the case of the pipes of a church organ ; 

 which shows that organs built for cold conn- 



