470 Dr. C. R. A. Wright and Mr. C. Thompson. [Mar. 28, 



the portions of the ingots analysed did not truly represent the com- 

 position of the lighter and heavier alloys whilst molten. To avoid 

 this we devised an arrangement whereby we could draw samples 

 from the molten mass whilst still fluid. This consisted of a crucible 

 holding some 500 to 600 grams of molten alloy, with a hole drilled 

 through the bottom, closed by a conical plug worked up and down by 

 means of a screw and lever. At the required moment, by turning the 

 lever the plug could be slightly raised by the screw, so that a little of 

 the lowest layer of molten metal escaped through the valve thus 

 opened into an ingot mould placed to receive it. Simultaneously the 

 top layer of molten metal could be sampled by a hot porcelain spoon. 

 The crucible was surrounded by a cylindrical clay jacket to keep in 

 the heat, which was supplied by a number of bunsen burners arranged 

 so as to form a ring of flame between the crucible and jacket. Ap- 

 parently there was no reason whatever why this arrangement should 

 not work successfully ; but in practice we did not succeed in getting, 

 by its means, any results at all on which reliance could be placed. 

 The analyses indicated that instead of this arrangement giving more 

 complete separation than the pipe-bowls, it hardly ever gave so com- 

 plete a one; on drawing samples at different times, instead of the 

 separation gradually becoming more perfect as time elapsed, the 

 opposite was often the case, some intermixing influence being ap- 

 parently at work, which frequently was more powerful than the 

 effect of gravitation in causing the lighter and heavier alloys to 

 separate from one another. For instance, the following numbers were 

 obtained in one experiment, indicating very incomplete separation as 

 compared with the pipe-bowl results : 



In another case no sensible separation at all was brought about 

 after either four or eight hours with a mixture that separated readily 

 when fused in a tall narrow crucible. 



These particular two experiments are extreme cases as to irregu- 

 larity ; but still, in almost every instance, the figures obtained with 

 the valve crucible were such as to show that the separation of heavier 

 and lighter alloys from one another therein was extremely imperfect. 



