210 EXPERIMENT STATION EECORD. 



of the substance burned without the addition of alkalis, etc., yielded 

 only 0.417 per cent. 



Many chemists in preparing the ash in platinum dishes, whether 

 over a flame or in the muffle, first extract the fusible salts from the 

 charred substance with water, then dry and incinerate the residue 

 completely, afterwards adding the extract, evaporating, and gently 

 glowing. 



SPECIAL INCINERATING APPARATUS. 



In order to regulate the admission of air to the substance and at 

 the same time to retain the volatile substances, several forms of appa- 

 ratus have been proposed in which the substance is burned in a current 

 of air or oxygen, and the volatile portion or fine particles collected. 

 Konig used simply a glass tube drawn out to a point for discharging a 

 small current of oxygen into the faintly glowing substance. 



Mitscherlich ^ and Schloesing ^ heated the substances in a platinum or 

 silver boat placed in a wide glass or porcelain tube, through which a 

 current of carbon dioxid was first passed, until the charring was com- 

 plete and combustible gases ceased to be given off, and then a current 

 of oxygen, and the incineration completed. By this means there should 

 hardly be any volatilization of substance and no inclosing of carbon 

 by the fusing of the salts. A similar apparatus has been recommended 

 by Reese. ^ 



Hlasiwetz * employed a double-necked flask, in one opening of which 

 a porcelain tube was placed in a perpendicular position, wide above 

 and narrow below, with a sieve of platinum in the bottom upon which 

 the substance was placed. The substance was ignited and air was 

 drawn through the tube and the bottle l)y means of an aspirator until 

 the combustion was complete. The products of combustion were 

 passed through the water in the flask, which held any particles carried 

 along mechanically, as alkaline chlorids, etc. The incineration was 

 completed in a platinum dish. 



Shuttleworth'' and Tucker,® working in the Agricultural-Chemical 

 Laboratory of the University of Gottingen, have recently made use of 

 another principle. They emploj^ed a specially constructed platinum 

 crucible of large size, with a platinum cover carrying a tube reaching 

 to the bottom of the crucible, through which a current of air was con- 



^ Jour. Prakt. Chem., 36 (1845), p. 232. 



^ Contributions a Tetude de la cliimie agricole, p. 225. 



''Ztsclir. Analyt. Chem., 27 (1888), p. 133. 



*Ann. Chem. u. Pharm., 97 (1856), p. 243. 



sjour. Landw., 47 (1899), p. 173 (E. S. R, 11, p. 304). 



«Ibid., 48 (1900), p. 64 (E. S. R., 11, p. 506). 



