1839.] 



On Chemical Tests. 



325 



lution is neutral, a white flocculent precipitate will fall, indicating 

 magnesia. Filter the solution, and add hydrofluosilic acid; after some 

 time a precipitate will be formed, indicating barytes. Filter, and to 

 the remainder of the solution add water, diluting it largely ; then add 

 dilute sulphuric acid, and a precipitate will fall indicating strontian. 

 After this has completely separated, to the clear solution add oxalate 

 of ammonia, and a cloudiness will indicate the presence of lime. In 

 this case all 4 substances are supposed to be present, but if the tests 

 do not act, as above stated, the absence of that substance to which the 

 test is appropriate is to be inferred, see 115, b. c. d. e. 44 c. and 75, b. 



e. Lime and magnesia may be thus separated. To the solution add 

 oxalate of ammonia, slightly acidulated with oxalic acid, collect the 

 precipitate, wash, and dry it at 212.° 100 parts of the dry precipitate 

 indicate 38 or 39 of lime. Another process is to add muriate of am- 

 monia to a muriatic solution of lime and magnesia, and afterwards to 

 add caustic ammonia slightly in excess; if necessary, filter. Then add 

 oxalate of ammonia, and separate the oxalate of lime by filtration. Phos- 

 phate of soda, or phosphate of ammonia now added will precipitate the 

 magnesia,"as an ammonia magnesian phosphate, which dried at a heat of 

 100 3 probably consists of 



Ammonia 1 17 14.41 



Magnesia 1 20 ...... 16.96 



Phosphoric acid 1 ...... 36 30.45 



Water 5 45 38.18 



1 118 100.00 



SO. MAGNESIA, carbonate of, see 25, 65 c, 



81. MANGANESE. Liquid potash, soda, or ammonia produces in a 

 solution containing manganese a white precipitate, insoluble in an ex- 

 cess of the alkali, changing to brown, and at the point of contact with 

 the atmosphere, to black. Carbonate of potash produces in solutions 

 of proto-salts of manganese a white precipitate, which on exposure to 

 the air, does not change colour, but remains white. Prussiate of potash 

 produces a white or pale red precipitate which is soluble in free acids. 

 Hydrosulphurets produce a white, grey, or reddish precipitate. Chlo- 

 ride of soda (common salt) dropt into a solution of protoxide of man- 

 ganese produces a black bulky precipitate of deutoxide of manganese. 



a. The following tests discriminate manganese more particularly. 



