Prof. R. Bunsen on Flame Reactions. 87 



easily made out of one ordinary-sized test-tube, by softening the 

 glass before the blowpipe, and then drawing it out until the re- 

 quisite size of tube is obtained. This long tube is then cut up 

 with a diamond into pieces 6 to 8 centims. long, and each of 

 these again divided into two over the lamp, and the closed ends 

 neatly rounded. The sample having been finely powdered with the 

 knife- blade (fig. 4, a) on the porcelain plate (fig. 3), is treated 

 in a tube either by itself, or with a mixture of carbon and soda, 

 or with sodium or magnesium. A piece of magnesium wire a 

 few millims. in length is for this purpose pushed down into the 

 powdered sample contained in the glass tube ; the sodium is care- 

 fully freed from rock-oil and rolled out between the fingers to a 

 small cylinder, which is then surrounded by the powdered sub- 

 stance. The best form of carbon is the soot from turpentine, 

 which has been deposited upon the outside of a basin filled with 

 cold water. As soon as the small tube containing the perfectly 

 dry sample has been heated to the point of fusion of the glass, 

 when generally an ignition inside the tube is noticed, it is allowed 

 to cool and then placed upon the porcelain plate, covered by a 

 piece of paper and crushed to powder with the knife, for the pur- 

 pose of further examining the products of reduction. 



2. Reduction on splinters of Charcoal. — In this way the metal 

 can be obtained in small globules, or as a porous mass, from 

 quantities often less than a milligramme of the sample. 



A transparent crystal of sodium-carbonate is brought near to 

 the outside of the name, and a common wooden lucifer-match 

 then rubbed over two-thirds of its length with the drops of fused 

 salt. If the match is then turned upon its axis through the 

 flame, the carbonized wood becomes surrounded with a crust of 

 solid sodium-carbonate, which, on heating in the zone of fusion, 

 melts and is absorbed by the carbon. A splinter of charcoal is 

 thus obtained, which is prevented from burning by its glaze of 

 soda. A mixture of the substance is then made with the knife 

 upon the hand with one drop of the melted soda-crystal, and a 

 portion of this, of the size of a mustard-seed, placed upon the point 

 of the splinter. As soon as this has been melted in the lower oxi- 

 dizing flame, it is passed through a part of the dark interior zone 

 to the hotter portion of the lower reducing flame. The point at 

 which the reduction occurs is easily seen by the violent efferves- 

 cence of the soda ; and this is after a time stopped by bringing 

 the splinter into the dark zone. In order to isolate the reduced 

 metal, the end of the splinter is broken off and rubbed up with 

 a few drops of water in a small agate mortar, when the metallic 

 particles are generally visible without removal of the carbon. 

 For further examination, the carbon and soda can be easily re- 

 moved by several careful washings, and the particles transferred 



