108 SALTS OF BARYTA. 



still requires purification, as the best tvus procured contains bui 50 pei 

 cent, of the pure acid. 



It is employed in the manufacture of borax. Boron occurs in nature 

 also, in datholite, tourmaline, and a few other species, but these are not 

 a sufficient source to be employed in the arts. 



Thenardite. Thenardite is an aahydrous sulphate of soda from Es- 

 partine in Spain. . 



Gay-Lussite. Occurs in oblorg crystals, in a lake in Maracaibo 

 S. A. ; it is a hydrous compound of the carbonates of lime and soda. 



Glauberite. In oblique cystals, (usually flattened, with sharp edges, 

 nearly transparent and yellowish-gray in color. Taste weak, slightl> 

 saline ; consists of 49 per cent, of sulphate of lime and 51 of sulphate of 

 soda. Occurs in rock salt at Villa Rubia, Spain, and also at Aussee ia 

 Upper Austria, and Vic in France. 



4. BARYTA. 

 The salts of baryta are distinguished by their high specific 

 gravity, which ranges from 3*5 to 4*8. They resemble the 

 salts of strontia, and some of the metallic salts. From the 

 latter they are distinguished by giving no odor nor metal- 

 lic reaction before the blowpipe, when pure. Hardness 

 below 4. 



heavy star.— Sulphate of Baryta. 



Trimetric. In modified rhombic and rectangular prisms, 

 1 (figs. 1, 2) M : M = 101°40; _* 



P : a = 141° 10 ; P : a = 127° 



18'. Crystals usually tabular. 

 Massive varieties often coarse 

 lamellar ; also columnar, fibrous, granular and compact. 

 Luster vitreous ; color white and sometimes tinged yellow, 

 red, blue or brown. Transparent or translucent. H =2*5 — 

 3'5. Gr = 4*3 — 4*8. Some varieties are fetid when rubbed. 



Composition : sulphuric acid 34, baryta 66. Decrepitates 

 before the blowpipe and fuses with difficulty. 



Dif. Distinguished by its specific gravity from celestine 

 and arragonite, and also by not effervescing with acids from 

 the various carbonates ; from the metallic salts, by no metal 

 lie reaction before the blowpipe. 



Obs. Heavy spar is often associated with the ores of 



What is a striking character of the salts of baryts 1 How are they 

 distinguished from salts of the metals 1 What are the fonns of the crys- 

 tals of heavy spar 1 What are the colors ] What is the composition 1 



