Improved apparatus for the analysis of coal, and for organic analysis generally
Journal of the Franklin Institute
purpose; what I elaim is, the employment of the rotating concentric hub, on which the toes, or their eqnivalents~ of the lifters, rest~ when the valves are closed, substantially a~ specified, when this is combined with a cam connected therewith, and which turns eceen. trieally thereon, for the purpose of opening and closing the valve, and regulating the pc. rim of closing the same, substantially as specified. And I also claim combining with the ~aid hub and cam, a slide within them, and acting
... n an oblique groove within the cam, and a straight slot in the hub, substantially as specified, to determine the period of closing the valve, whilst the period of opening remains the same~ as specified; and this [ elaiah whether the said slide be operated by a governor, or by other means. Early in October last, having to make an ultimate analysis of divers specimens of coal, anthracite and bituminous, we had also abundant op. portunity of observing the want of certainty and uniformity of result in the methods ordinarily recommended and practised for such analysis. With all these methods, where the aim is to induce the organic or other substance under analysis to give off its carbon by combustion, in glass tubes, with oxide of copper, chromate of Jead, or chlorate of potassa, either separately or mixed ; and where the effects arise under a simple play of affinities at a high temperature, and are unaided by any external tbrce or mechanical agency, variations occur to such an extent, as, in the case of anthracite coal especially, to leave the results, from several assays of the same sample, rarely identical. We have found these variations to depend, among other things, upon the grade of comminution of the matter for analysis, and its mode of intermixture with the oxidizing agents. If, for instance, the coal is too finely divided, it either protects, or is protected by tile re-agents against the effect of the heat ; although this may be so high as to thse the tube and part of its contents. If, on tile other ]land, the coal be not finely divided enough, it protects itse/f. We all know the extreme difficulty of driving off the carbon fi'om an anthracite coal, for example, even in an open crucible and over a blast; where sometimes three hours and more are spent in reducing so small a qnm~-Iity as one gramme to ashes. And as for the mode ofintermixt~re which shall be most favorable tbr the expos~Jrc and c(mlact of the greatest amount of surface between the material and re-agen.~ respectively, it is easy to see that, even after having been studied and altained in orJe instance, its repetition must be more the gift of good fortune than the result of any regular and unfailing manipulation. Again, in the ordinary methods, with whatever re-agent, the heat: necessary to be applied, and the apparatus tbr its application, prevent in a great degree, if nc~t eutireb", the experimenter fi'om observi~lg what is going' on in the tube; so lh}~i lie is left without any optical grounds, or indeed any grounds at all, beyond die cessation of tJubbles in the potash bulbs and'an ini)reuee ti'om the lapse of time, for judging whether the operation is properly complete or not.