CONTRIBUTIONS TO BLOWPIPE ANALYSIS. 345 



8. METHOD OF DISTINGUISHING THE MONOXIDE OF 

 IRON (FeO) FROM THE SESQUIOXIDE (Fe^O^) IN 

 SILICATES AND OTHER COMPOUNDS. 



[First published in the Chemical Gazette : March 1, 1848.] 



This test serves to indicate, with great certainty, the presence or 

 absence of FeO in bodies generally. It is performed as follows : — A 

 small quantity of black oxide of copper (CuO) is dissolved in a bead 

 of borax on platinum wire, so as to form a glass which exhibits, on 

 cooling, a decided blue colour, but which remains transparent. To 

 this, the test-substance in the form of powder is added, and the whole 

 is exposed for a few seconds, or until the test-matter begins to dissolve, 

 to the point of the blue flame. If the substance contain Fe'^O^ only, 

 the glass on cooling will remain transparent, and will exhibit a blueish- 

 green colour. On the other hand, if the test-substance contain FeO, 

 this will become at once converted into Fe^O^ at the expense of some 

 of the oxygen of the copper compound ; and opaque red streaks and 

 spots of Cu^O will appear in the glass, as the latter cools.* 



Note : — Although this test is quoted by Plattner — perhaps the 

 best criterion of its accuracy — it is passed over, without mention, in 

 many works on chemical analysis. The writer may therefore be 

 allowed to call to mind, in proof of its efficacy, that by its use in 

 1848 he pointed out the presence of FeO in the mineral Staurolite 

 (Chem. Gaz,, July 15, 1848; see also Erdmann's Joiirnal filr praet. 

 Chem., XLVL, 119), nearly thirteen years before this fact — now 

 universally admitted — was discovered and announced by Ramm^lsberg 

 i^Berichte d. Kongl. preuss. Akad. d. Wiss, zu Berlin : Marz, 1861.) 



pipe characters of Phosphocerite were given in a paper on that mineral, pub- 

 lished in the journal of the Chemical- Society of London in 1848; and these 

 characters are referred to, from the paper in question, in the third volume of 

 Henry Watt's English translation of Oinelin's Handbuch, published by the Caven- 

 dish Society in 1849, as well as in both ihe third and fourth editions of Dana's 

 System of Mineralogy. 



* Provided too much copper oxide be not dissolved in the glass — so as to 

 become reduced per se — this test may be performed with either a reducingor 

 an oxidating flame. If the method be tried with a few bodies of known com- 

 position (in some of vrhich FeO is present, and in others absent) the operator 

 will see, at once, that it offers no risk of failure — always assuming, of course, 

 the absence of other reducing bodies, a point easily ascertained by the blowpipe. 



