78 Intelligence and Miscellaneous Articles. 



it fuses into a transparent pearly bead, which becomes opake on 

 cooling. On heating this glass in the reducing flame, the reaction 

 indicating titanic acid (a red colour) is not perceptible ; most fre- 

 quently it is of a pale violet colour, like titanic acid with borax. 

 Tachylyte in powder fuses into a greenish bead, which is without 

 bubbles, and is transparent even after cooling ; strong hydrochloric 

 acid acts upon it, even when cold, and separates gelatinous silica ; 

 and in analysing it the action of this acid was continued till the 

 titanic acid was dissolved by avoiding the degree of heat which 

 would have rendered it insoluble. 

 The results of the analysis were— 



Silica 50*220 



Titanic acid 1*415 



Alumina 17*839 



Lime 8*247 



Soda 5-185 



Potash 3-866 



Magnesia 3-374 



Protoxide of iron 10-266 



manganese 0*397 



Ammoniacal water .... 0*497 



101-306 

 The tachylyte does not contain titanic acid in the state of tita- 

 niate of iron, for this is not acted upon by cold hydrochloric acid ; 

 the calcined mineral is also acted upon by this acid, but the silica is 

 of a brown colour. — Annates des Mines, tome xvii. 



ANALYSIS OF NATIVE ALUMI NATES. 



M. II. Rose states that native aluminates which are decomposed 

 with so much difficulty and so imperfectly by the .alkaline carbonates, 

 and even by hydrate of potash, which also resist the action of hy- 

 drofluoric acid> and in the analysis of which Abich has so success- 

 fully employed carbonate of barytes, are completely and readily de- 

 composed by fusion with bisulphate of potash. 



He first employed it in the analysis of the chlorospinelle of Fla- 

 tonsk : this mineral was reduced to fine powder in a steel mortar 

 without having been previously bruised in an agate, flint or chalce- 

 dony mortar, was heated with bisulphate in a platina crucible over a 

 spirit-lamp with a double current of air, until the powder was com- 

 pletely dissolved. 



The fused mass dissolved entirely in water, and the constituent 

 principles of the solution may be determined by the well-known 

 methods. The alumina, when the quantity is not too small, ought 

 to be redissolved in hydrochloric acid, and precipitated by carbonate 

 of ammonia, to avoid an excess of it in the result. The use of the 

 bisulphate of potash especially requires this precaution, because the 

 salts of the fixed alkalies are separable with so great difficulty from 

 precipitated alumina by washing. 



M. Rose did not find any silica in the chlorospinelle, although 



