374 Intelligence and Miscellaneous Articles. 



satisfied. For some time past I have no longer employed bulb 

 tubes in reductions by means of hydrogen gas, but place the sub- 

 stance to be reduced in a platinum or porcelain crucible, provided 

 with a platinum lid, which is perforated in the centre, into which 

 passes a curved silver tube about 8 inches long, through which the 

 dried hydrogen is conveyed into the crucible. During ignition the 

 gas escapes between the lid and crucible. Ebelmen* has recently 

 employed a similar apparatus for the reduction of the sesquioxide of 

 manganese to the state of protoxide. This apparatus can be used 

 with considerable advantage for burning the charred mass. The 

 crucible is half-filled with the substance, and heated over a spirit- 

 lamp, while a current of oxygen is passed into it ; with proper care 

 not a particle of ash is carried away, and the combustion proceeds 

 very rapidly ; a further quantity of the substance is conveyed from 

 time to time into the crucible. By this means the ash obtained may 

 be weighed with such accuracy as would not be easily accomplished 

 in any other waj'. 



When the combustion is efi'ected in a platinum crucible, this is 

 sometimes acted upon ; a silver crucible is liable to partial fusion 

 from the heat during the combustion ; it is therefore advisable to 

 employ a porcelain crucible, which is acted upon far less than glass ; 

 and if very thin and somewhat transparent, the progress of the com- 

 bustion may be distinctly observed by the incandescence. 



The weight of the ash obtained, added to that of the evaporated 

 aqueous extract of the charred mass and to that of the insoluble 

 earthy salts dissolved by the hydrochloric acid, gives the correct 

 quantity of fixed constituents in the organic substance employed. 



The ash obtained, especially when derived from vegetable sub- 

 stances, consists of the same constituents as were found in the aqueous 

 and acid extracts ; if alkalies were present in them, we likewise find 

 them in the ash of the exhausted charred substance ; otherwise it 

 consists principally of earthy phosphates. I have already mentioned 

 that nearly the whole of the iron of the blood is met with in this 

 ash. Only about the tenth part of it is found in the acid extract of 

 the charred mass, and indeed the less the more carefully the charring 

 was effected with exclusion of the air. When the organic substance 

 contains no silica, various views may be entertained respecting the 

 origin of the ash from the charred mass which has been exhausted 

 with water and acid. The most probable is perhaps to derive it 

 from an imperfect exhaustion with the two solvents. When an 

 organic substance is destroyed by heat, the charcoal formed may 

 contain such cavities tliat the inorganic salts surrounded by them 

 are protected from the action of tlie solvents. The globules of the 

 blood, those of yeast, the cells of plants, form perhaps after charring 

 extremely minute vesicles, with such small apertures that no liquid 

 can penetrate into them. That the vessels of wood are capable of 

 forming extremely tliin filaments with minute apertures by charring 

 is known from the investigations of Degcnf. The charred mass of 

 an organic substance (yeast), alter it had been most carefully ex- 

 * Clicui. Gaz., vol. i. p. 685. f Poggendorff's Annalcu, vol. xxxv. p. 468. 



