169 



23. SULPHURIC ANHYDRIDE. S 8 . (Sulphuric Oxide, Trioxide of 



Sulphur, Anhydrous Sulphuric Acid.) 

 a. In white acicular crystals. 

 Note. This specimen was presented by Messrs. Hopkin and Williams. 



24. SULPHURIC ACID. (Oil of Vitriol, Vitriolic Acid.) 



a. Commercial acid, impure. Sp. gr., 1'843. 



b. Purified. (Acidum Sulphuricum, B.P.) 



c. Glacial sulphuric acid. (Hydrate of Sulphuric Acid.) 

 Note. This specimen has a sp. gr. of 1-78. At 47 F. this hydrate 



forms large prismatic crystals. Formula 1L S 0., I L 0. 



d. Fuming sulphuric acid. (Nordhausen Sulphuric Acid.) 



SELENIUM. SE. 



25. METALLOID. 



t a. Crystalline. 



f 6. Amorphous. 



Note. Specimen b consists of a medallion made of amorphous sele- 

 nium in honour of Berzelius, the discoverer of this element, and hears 

 an impression of his bust upon it. 



For remarks upon the allotropism of selenium, see P. J. [1] , vol. xvi., 

 p. 169. 



26. SELENIOUS ACID. H Se 0,. 



* o 



t a. Crystals. 



Note. The red tint of this specimen is due to the presence of free 

 selenium. The crystals have deliquesced slightly although efflorescent in 

 dry air. 



27. SELENIC ACID. H 2 Se 4 . 



t a. Liquid. 



TELLURIUM. Te. 



28. METALLOID. 



t a. In small nodules. 



29. TELLURIDE OF BISMUTH. 



t a. Native, in small crystals. 

 Note. See also a specimen in the central case, No. 8. 



BORON. B. 



30. METALLOID. 



t a. Crystals, 

 t b. Amorphous. 



31. BORACIC ANHYDRIDE. B 3 3 . 



a. Obtained by heating boracio acid. 



32. BORACIC ACID. H 3 B 8 . (Boric Acid, Hamberg's Sedative Salt.) 



a. Crude, obtained fw>m the lagoons of Tuscany. 



