Adeney&Shegog— TFet and Dry Methods in Chemical Analysis. 107 



Difficultly Reducible Metallic Oxides. 

 Iron, Chromium, Aluminium, Cobalt, and Manganese. 



Experiments were made with the compounds of the above- 

 mentioned metals, as with the compounds of the easily reducible 

 oxides. The results were somewhat surprising. In each case, the 

 silver immediately on reduction, became infusible, or very diffi- 

 cultly fusible, but on heating the reduced silver for a long time, 

 with the tip of a good oxidizing flame, it could in all cases be 

 made fusible. 



Under the conditions of the experiment, it was thought pro- 

 bable that these metals were, at least to a small extent, reduced. 

 It seemed to us possible that a small quantity might become 

 reduced before the substance could be dissolved in the borax ; and 

 if this occurred, we should expect the alloy formed to be infusible 

 or difficultly fusible. 



To avoid such possible reduction, the substances were first 

 fused with borax alone on charcoal, in the oxidizing flame, the 

 glass bead was then powdered, mixed with the silver chloride, and 

 heated in the reducing flame, the results were not more satisfactory, 

 the metallic bead in each case became infusible soon after reduc- 

 tion. It was found that small quantities of iron and cobalt were 

 reduced even when their compounds were heated with borax alone 

 in the oxidizing flame, the reduced metal was always found as a 

 thin film or small globules on that surface of the glass which had 

 cooled in contact with the charcoal. In each of these experiments 

 the weight of substance taken was 3 decigrams, and of borax 12 

 decigrams. 



Some experiments were next made with cobalt chloride, to 

 ascertain whether by decreasing the weight of salt experimented 

 upon, this reduction could be prevented, It was found that even 

 when a mixture of 1 centigram of cobalt chloride, and 40 centi- 

 grams of borax were fused in the oxidizing flame, some cobalt was 

 reduced, though only a very minute quantity. 



In the experiments with cobalt, the metallic bead always 

 became very difficultly fusible ; and on solidifying it entirely lost 

 its globular form, and flattened out in a very remarkable manner, 

 sometimes even becoming branched. A similar flattening of the 



SCIEN. PROC. R.D.S. VOL. Til., PAliT II. K 



