M. Gaudin on Soluble Aluminate of Baryta. 27 



mina as 2 : 1. The substances were placed in a sealed tube, and 

 at once solidified in the cold. Heated to about 170°, the magma 

 was changed into a colourless liquid, which was separated by 

 decantation from small limpid hexagonal tables ; under the 

 polariscope these exhibited the coloured rings and black cross 

 characteristic of the rhombohedral system. The analysis showed 

 that this substance was Levyne, Al 2 O 3 SiO 3 CaO Si0 3 + 6HO. 



When the same mixture was heated to a higher temperature, 

 a sand was produced which was nothing but crystallized silica, 

 accompanied by a small quantity of Levyne. 



By altering the relative proportions of silica and alumina, 

 variable results were obtained. A mixture of silicate and alumi- 

 nate of potash gelatinized at the ordinary temperature, but was 

 transformed at 200° into a crystalline sand which had the com- 

 position of Phillipsite. 



Deville has found that aluminate of baryta may be formed, 

 either by calcining the nitrate or carbonate of baryta with an 

 excess of anhydrous alumina, or by precipitating sulphate of 

 alumina by baryta. 



M. Gaudin has observed* that when steam is passed over 

 a mixture of ferruginous alumina, charcoal, and chloride of 

 barium, or, what is more economical, sulphate of baryta, an 

 aluminate of baryta is formed ; the sulphuric acid of the sulphate 

 of baryta passes off in the form of sulphide of carbon, sulphur, 

 sulphurous acid, and sulphuretted hydrogen. The aluminate of 

 baryta is soluble, differing in this respect from the aluminates of 

 lime and magnesia. Lime-water added to the solution produces 

 an immediate precipitate of aluminate of lime. 



Aluminate of baryta is well fitted for preparing solution of 

 pure alumina : it is merely necessary to add to the solution suffi- 

 cient sulphuric acid to precipitate the baryta; the alumina 

 precipitates at the same time ; but by adding either excess of 

 sulphuric acid, or acetic or nitric acid, the alumina passes into 

 solution, while the sulphate of baryta remains undissolved. 



According to Wohlerf, when nitrate of soda is heated in 

 closed vessels with binoxide of manganese, no manganate of soda 

 is formed, — the reason doubtless being that nitrate of soda is 

 decomposed before the temperature is attained at which man- 

 ganic acid is formed. The decomposition is so complete that 

 this deportment may be used for the preparation of pure caustic 

 soda. 



By fusing together tungstate of soda with chloride of calcium 



or chloride of lead, Manross obtained the tungstates of these 



* Comptes Renclus, March 24, 1862. 

 f Liebig's Annalen, September 1861. 



