84 URANIUM, ANTIMONY, CHROMIUM, &c. 



covered by a brownish shining crust. This crust 

 becomes white when heated to redness, but still 

 appears as if the whole were coated with varnish. 

 When titanic acid is precipitated by ammonia, 

 and the dried bulky precipitate is heated to red- 

 ness, we obtain a mass cohering together, hav- 

 ing a brownish colour, an adamantine lustre, 

 and a good deal of resemblance to the native 

 oxide of titanium, called rutile. When titanic 

 acid heated to redness is laid upon litmus paper 

 and moistened with water, the liquid becomes 

 red, but the paper retains its blue colour. Ti- 

 tanic acid forms insoluble compounds with the 

 alkalies ; it combines with some acids, but does 

 not neutralize them. As an acid, it is nearly as 

 feeble as silica ; hence the difficulty of deter- 

 mining its atomic weight. Such are the pro- 

 perties of titanic acid determined by M. Rose. 



3. I shall now state the experiments which 

 have been made to determine the atomic weight 

 of titanic acid. 



(*') ^ ose P re P are d a sulphuret of titanium in 

 the following way : Titanic acid was made into a 

 paste with water, dried, and heated to redness. 

 By this contrivance it formed a cohering mass, 

 which was put into a porcelain tube ; a small 

 retort, containing bisulphuret of carbon, was 

 luted to one extremity of this tube, and a glass 

 tube to the other extremity. The porcelain tube 

 was heated to redness, and then the bisulphuret 



