106 Progress of Foreign Science. 



of potash is heated to the boiling point, a great deal of ammonia 

 is disengaged, and carbonate of potash remains dissolved. 



Cyanate of silver is obtained in the form of a white powder, 

 by precipitating a solution of nitrate of silver, with cyanate of 

 potash. This salt of silver, treated with acids, evolves carbonic 

 and cyanic acids, and an ammoniacal salt is generated. It is very 

 soluble in aqueous ammonia, by the evaporation of which, large 

 semitransparent crystalline plates are formed, resembling quickly 

 crystallized hydrate of barytes. These constitute cyanate of silver 

 and ammonia. — A cyanate of lead is obtained in the form of a 

 thick white precipitate by mixing solution of acetate of lead, with 

 one of cyanate of potash. It appears in small needles, like muri- 

 ate of lead, and is like it soluble in hot water. It is composed in 

 100 parts of 75 oxide of lead, and 25 cyanic acid. From the 

 igneous analysis of this salt, M. Wb'hler infers the composition of 

 the acid to be, — 



Carbon 31.664 



Azote 36.940 



Oxygen 31.396 



100.000 



From theoretical considerations he offers the following modified 

 statement of these proportions as probably more correct. 



Carbon ... 2 atoms 35.294 



Azote .... 1 „ ........ 41.177 



Oxygen ... 1 „ 23.529 



100.000 



As the atomic weight of the acid thus becomes 4.25, its com- 

 pound with oxide of lead=14, should give per cent. 76.713 oxide 

 to 23.287 acid, instead of 75 and 15, as by the above experimental 

 result. — Gilbert's Annalen, lxxiii, 157. 



7. On Felspar, Albite, Labradore, and Anorthile. By Gustavus 



Rose, of Berlin. 

 Some differences which Mr. Rose observed in the angles of cer- 

 tain crystals, hitherto classed among the felspars, led him to 

 make a closer investigation of them ; the result of which was, 

 that under these crystals are contained four species, differing both 

 in a crystallographical and chemical point of view, though in the 

 former respect they exhibit an undoubted analogy. 



Felspar proper, KS 3 + 3 AS 3 , is the most abundant of these 

 species. To it belong the Adularia of St. Gothard, the glassy 

 felspar of Vesuvius and the Siebengebirge, the Amazon-stone of 

 Siberia, the Labradore-felspar from Friedrichswarn in Norway, 

 the felspar of Baveno, Carlsbad, and the Fichtelgebirge, and ge- 

 nerally most part of Werner's common felspars. 



