342 CONTRIBUTIONS TO BLOWPIPE ANALYSIS. 



3. DETECTION OF ALKALIES IN THE PRESENCE OF 



MAGNESIA. 



[Fird published in the Chemical Gazette : September, 1847 .] 



In the analysis of inorganic bodies, magnesia and the alkalies (if 

 present) become separated from other constituents towards the close 

 of the operation. In continuation of the analysis, it then becomes 

 desirable to ascertain, at once, whether magnesia is alone present, or 

 whether the saline mass, produced by the evaporation of a portion of 

 the solution, consists of magnesia and one or more of the alkalies, or 

 of the latter only. • By fusing a small quantity of the test-matter with 

 carbonate of soda, the presence of magnesia is readily detected, as this 

 substance remains undissolved ; but the presence or absence of alka- 

 lies is not so easily determined, the coloration of the flame being fre- 

 quently of too indefinite a character to afford any certain evidence on 

 this point. The question may be solved, however, by the following 

 simple process. Some boracic acid is to be mixed with the test-matter 

 and with a few particles of oxide of copper, and the mixture is to be 

 exposed for a few seconds, on a loop of platinum wire, to the action of 

 an oxidating flame. In the absence of alkalies, the oxide of copper 

 will remain undissolved ; but if alkalies be present, an alkaline borate 

 is produced, forming a readily fusible glass, in which the copper oxide 

 is at once dissolved, the glass becoming green whilst hot, and blue 

 when cold. If magnesia also be present, white specks remain for a 

 time undissolved in the centre or on the surface of the bead. Any 

 metallic oxide which imparts by fusion a colour to alkaline borates,, 

 may, of course, be employed in place of oxide of copper ; but the lat- 

 ter has long been used in other operations, and is therefore always 

 carried amongst the reagents of the blowpipe-case. 



4. REACTION OF MANGANESE SALTS ON BARYTA. 



[First published in Chemical Gazette : August 1, 1846.] 



"When moistened with a solution of any manganese salt, and ignited 

 in an oxidating flame. Baryta and baryta compounds, generally, 

 assume on cooling a blue or greenish-blue colour. This arises from 

 the formation of a manganate of baryta. Strontia and other bodies 

 (apart from the alkalies) when treated in this manner, become brown 

 or dark-grey. A mixture of baryta and sti'ontia also assumes an 



