Hautefeuille : Artificial formation of Sphene and Perowskite. 251 



He draws the conclusion that proofs are wanting of the presence 

 of nitrogen in steel, and still more so of the necessity of nitrogen 

 as a steel-forming body. It follows from various investigations, 

 that iron can pass into steel when placed in contact at a high 

 temperature with bodies free from nitrogen, but that, on the 

 other hand, the volatile cyanogen compounds are to be regarded 

 as bodies specially suited for the formation of steel. 



Rudorff* describes a method for determining the quantity of 

 carbonic acid in coal-gas, which in the absence of the usual gaso- 

 metric apparatus may be used with advantage. The principle of 

 the method consists in absorbing the carbonic acid by concen- 

 trated potash, and replacing the carbonic acid which disappears 

 by an equal volume of caustic potash ; but without a figure a de- 

 scription would not be easily intelligible. 



Hautefeuille describes the artificial formation of sphene and 

 Perowskite j\ To prepare the former, three parts of silicic acid 

 and four of titanic acid are introduced into a large platinum cru- 

 cible, which after being filled with chloride of calcium and suit- 

 ably protected, is rapidly raised to a high temperature. The 

 mass when cold is treated with acidulated water, which dissolves 

 the excess of chloride of calcium and a little silicate of lime. In 

 all cases under these circumstances crystals of sphene are formed ; 

 but their development is favoured by all the circumstances which 

 prolong the action of the chloride of calcium. It is probable 

 that the crystallization is not produced by simple fusion in the 

 gangue, but arises from the action of chloride of titanium on a 

 silicate of lime. A mixture of coarsely powdered rutile, silica, 

 and chloride of calcium gives, with a day's heating, a beautiful 

 crystallization. The pieces of rutile are covered with crystals of 

 sphene, just like the specimens from St. Gothard. 



Analysis of the artificial mineral gave numbers agreeing with 

 the formula SiO 2 , TiO 2 , CaO. 



At a red heat sphene in contact with chloride of calcium is 

 rapidly decomposed by aqueous vapour. The decomposition is 

 best effected by heating to bright redness in a platinum dish a 

 mixture of titanic and silicic acids with chloride of calcium, and 

 exposing it to the action of a stream of carbonic acid saturated 

 at 50° with aqueous vapour, or to that of a current of air satu- 

 rated with hydrochloric acid and moisture by passing through 

 hydrochloric acid. By repeated treatment of the residual mass 

 with hydrochloric acid and aqueous potash, crystals are obtained 

 which have all the physical, crystallographical, and optical pro- 

 perties of natural titanate of lime, Perowskite, CaO TiO 2 . 



* PoggendorfF's Annalen, May 1865. 

 f Comptes Rendus, vol. lix. p. 68. 



