488 PROCEEDINGS OF THE AMERICAN ACADEMY 



aggregations, which appear black by ti-ansmitted, and grayish-black 

 by reflected light. When the bead saturated with iron is heated for 

 some time in the ordinary reducing flame, and, when quite cold, a small 

 portion of its surface exposed for a few seconds to the influence of the 

 small fine-pointed reducing flame, the precipitate Avhich forms is ap- 

 parently metallic. When a bead, nearly opaque with sesquioxide of 

 iron, is thoroughly fused in the outer flame, teroxide of antimony added, 

 and then reheated for a short time in the same flame, a gray metallic- 

 looking precipitate forms on the surface, upon cooling. Substituting 

 arsenious acid for antimony, the experiments otherwise being conducted 

 in the manner just described, I have obtained no precipitate whatever. 

 Lime and litharge seem to have but little effect on the iron reaction. 

 Upon adding the red oxide of manganese, I have noticed a dark 

 cloudy precipitate form in the glass, after treating with the reducing 

 flame ; but the reaction is very unsatisfactory. 



Uranium. — With borax, in the intermittent flame, sesquioxide of 

 uranium yields a light-colored flocculent-looking precipitate ; but no 

 crystals, so far as I have observed. In the reducing flame, the precipi- 

 tate is very much like that of iron ; and addition of sesquioxide of 

 iron, or lime, does not sensibly affect it. Manganese produces, in the 

 reducing flame, the same precipitate that it does with iron. 



In microcosmic salt, I have obtained a crystalline precipitate ; but 

 the form of the crystals was not determinable, when magnified four 

 hundred diameters. This precipitate formed only after repeated ap- 

 plications of the reducing flame. Upon adding sesquioxide of iron, I 

 noticed crystals, in outline like those of strontia, but much smaller 

 than any that I have seen of that earth. 



Chromium. — Sesquioxide of chromium, fused with borax in the 

 outer, and then treated with an intermittent inner flame, yields a glass 

 filled with bubbles which are often microscopic. Reversing the pro- 

 cess, viz. first treating with the reducing flame, is followed by the 

 same result. With microcosmic salt, I have not obtained any differ- 

 ent reaction. Berzelius alludes to this phenomenon, in his treatise 

 on the blowpipe, stating at the same time his inability to account 

 for it. 



Tungstic Acid. — With borax, in the reducing flame, tungstic acid 

 readily yields a crystalline precipitate, often bluish at the edges, and 

 slightly iridescent. Under the microscope, this precipitate strikingly 

 resembles the arborescent crystallizations of frost upon window-glass 



