KJELDAHIv METHOD 



359 



which do not keep well mixed, especially when occasionally 

 shaken, should be intimately mixed before each weighing. The 

 sample is placed in a glass flask of about 150 cubic centimeters 

 capacity. The flask should be made of a special glass to with- 

 stand the conditions of the combustion. A globule of mercury 

 weighing a little less than one gram is placed in the flask and 

 also 20 cubic centimeters of pure sulfuric acid of 1.845 specific 

 gravity. The mercury is conveniently measured by an apparatus 

 suggested by Wrampelmayer. It consists of an iron tube hold- 

 ing mercury, and is conveniently filled, from time to time, from 

 a supply vessel placed in a higher position and joined by means 

 of a heavy glass tube and rubber tube connections. The lower 

 end of the iron tube is provided with a movable iron stopper 

 having a pocket just large enough to hold a globule of mercury, 

 weighing a little less than a gram. On turning the stopper the 

 pocket is brought opposite a discharge orifice and the measured 



Fig. 15. Moist Combustion Apparatus of the Halle Agricultural laboratory. 



globule of mercury is discharged. With substances which tend 

 to produce a strong foaming a little paraffin is used. The flasks 

 after they are charged are placed on circular digesting ovens 

 under a hood, as shown in Fig. 15. 



At first the tripodal support of the flasks is so adjusted as to 

 bring them between the lamps, and in this way a too rapid re- 

 action is at first avoided. After half an fiour the tripods are so 

 turned as to bring each flask directly over the lamp, the flame 

 of which is allowed to impinge directly against the glass. The 

 flame is so regulated that after the evolution of the sulfur dioxid 



