CHEMICAL SCIENCE. 177 



will not unite with it except in a nascent state, that is, while in the 

 act of being evolved. The only two substances known to combine 

 directly with nitrogen are, as MM. Wohler and St. Claire Deviile 

 have shown, boron and titanium ; the former a metalloid, much akin 

 to diamond, and the latter a somewhat rare metal. In 1829, M. 

 Despretz succeeded in effecting a combination of iron and nitrogen, 

 which before had been considered impossible. On this nitride of iron 

 M. Fremy lately presented a paper to the Academy of Sciences. 

 After confirming all M. Despretz's experiments, he announced a new 

 and easier method by which the nitride of iron may be prepared. This 

 consists in introducing into a porcelain tube about two hundred grammes 

 of anhydrous protochloride of iron, applying a strong red heat, and 

 then making a current of ammonia pass through the tube. This gas 

 will rapidly decompose the chloride, the iron taking possession of the 

 nitrogen of ammonia, and presenting, after the operation, a grayish, 

 and sometimes also a brilliant white metallic appearance. The ni- 

 tride of iron is very brittle, and is easily reduced to powder ; it is less 

 subject to oxidation than pure iron. Nitric acid acts slowly upon it, 

 while, on the contrary, it is rapidly attacked by sulphuric and hydro- 

 chloric acid. When dissolved in acids, the nitride of iron is decom- 

 posed, and gives rise to salts of iron and salts of ammonia. It is easily 

 and permanently magnetized like steel, but this property is not so 

 strong as in the latter. The nitride of iron will resist a red heat with- 

 out decomposition, but when heated in hydrogen it yields up its 

 nitrogen, which combines with the former and produces ammonia, and 

 nothing but pure iron is left besides. 



DIVERSE ACTION OF ACIDS ON IEON AND STEEL. 



M. Saint Eclure, a French chemist, has noticed that when an iron 

 rod is immersed in nitric acid of ordinary strength, the acid boils 

 about the surface of the iron, and this action is continuous ; but if 

 steel be used instead of iron, this action of the acid only lasts for a few 

 seconds, and then finally ceases. After the action of the acid has 

 ceased, the steel is said to be in a " passive " condition, and its capa- 

 bility of becoming thus "passive" completely discriminates it from 

 iron. The cause of nitric acid acting upon steel only to a very limited 

 depth, is the accumulation of carbon on the surface, as the iron of the 

 steel is taken up by the acid. 



FASTENING OF IKON BARS INTO STONE. 



For this purpose, lead is almost always employed, which forms a 

 voltaic couple with the iron, by which that metal is rapidly rusted. 

 Zinc, on the contrary, would preserve the iron. Dingier 's Polytecli. 

 Journal. 



CHEMISTRY OF STEEL. 



Much light upon the chemistry of steel has been obtained during 

 the past year, principally through the researches of the well-known 

 French chemist, M. E. Fremy, In a paper communicated to the 

 French Academy, he undertakes to prove that steel is not a carburet 



