C/iemical Science. 171 



exactly the quantity of sulphuric acid and magnesia, to learn 

 the nature of the alkali. 



Or, 2. Precipitate the magnesia and sulphuric acid by barytes 

 water, and the excess of barytes by carbonate of ammonia; 

 evaporate, calcine, and the alkaline subcarbonate is left pure. 

 The magnesia may be separated from the sulphate of barytes 

 by means of an acid. 



Or, 3. Precipitate the magnesia by lime water, the lime by 

 carbonate or oxalate of ammonia, evaporate, calcine, then the 

 magnesia is obtained immediately, and the alkali in the state of 

 sulphate. 



In examining a mineral for alkali, in the first instance, one 

 part of it powdered may be mixed with three parts of ceruse, 

 the mixture put into a crucible so large as to half fill it, 

 that crucible placed in another, and the whole heated to white- 

 ness, until it be perfectly fluid. Remove the small crucible, and 

 when cold, collect the glass, and those parts to which it adheres. 

 Pulverize it and boil in common muriatic acid. When it has 

 acted sufficiently, evaporate to dryness, and then wash with re- 

 peated small portions of boiling water. The silica will be left 

 with most of the lead in the state of muriate. Precipitate the 

 solution by lime water, which throws down all the other earths 

 and oxides, and then precipitate the lime by carbonate of am- 

 monia, boiling both together, evaporate to dryness, add a little 

 sulphuric acid to the residue and heat it, the alkali remains as a 

 sulphate. If there be no magnesia present, the lime water may 

 be spared, and the precipitation at once made with carbonate of 

 ammonia. — .draw, de Chim. xvii. p. 28. 



2. Compounds of Molybdenum, Chromium, Tungsten, Antimony , 

 Sfc — The following results are from a paper on the composition 

 of several inorganic combinations by M. Berzelius, They are 

 to be considered as the most accurate results to be obtained by 

 that chemist. 



Mo,,bda.«of,ead {SeonSd 



M I uj- 1 (Molybdenum . 



Molybdic acid k^^ •' 



•' (Oxygen 



{ Chromic acid 



(Oxide of lead 



(Chromium 



(.Oxygen . . 



rii • J / , (Chromium 



Chromic oxide (grcen)|Q^y^^^ 



Chromate of lead 

 Chromic acid 



Sulphuret of tungsten ] o i }, 



The blue substance which remains after the decomposition by 

 heat of tungstatc of ammonia in close vessels, is of a purticulai 



