and all of the sulphur must be fixed and oxidized to sulphate; third, 

 the method must be fairly rapid and not require a large amount of 

 practice, so that an analyst can make the determination from time to 

 time without great delay and difficulty. 



It is difficult to outline a method which will meet all of these con- 

 ditions, but after making quite a number of experiments the follow- 

 ing procedure was evolved, which seems to fulfill the requirements 

 more nearly than the peroxid method. 



THE PROPOSED METHOD. 



Weigh 1 gram of material in a nickel crucible of 100 cc capacity, 

 add 10 cc of a solution made by dissolving 100 grams of sodium nitrate 

 and 150 grams of sodium hydrate in 500 cc of water. Then add 5 

 grams of crystallized magnesium nitrate and stir with a platinum rod, 

 making sure that the mass is thoroughly mixed and that the sample is 

 broken up as much as possible. Wash down the material adhering to 

 the stirring rod and sides of the crucible with the smallest possible 

 amount of water. (This is essential since the addition of much water 

 will prolong the subsequent heating unnecessarily.) Heat for one 

 hour on a hot plate covered with a thin sheet of asbestos paper, keep- 

 ing the temperature at about 130 C. Then put the cover on the cru- 

 cible, tilting it in such a fashion as to leave an opening for the steam 

 to escape and heat further for one hour at from 150 to 160 C., or until 

 the material is entirely dry. If the fusions begin to bump, lower the 

 heat so that the covers will not be jarred down tight on the crucibles, 

 and the material lost by frothing. When the mass is entirely dry, 

 put the covers on tight and heat gradually until the temperature reaches 

 180 C., then heat for thirty-five minutes, maintaining the tempera- 

 ture at about 180 to 200 C. These temperatures were determined 

 by laying the thermometer down on the hot plate. 



Now set the crucible (with the cover on tight) into a round hole in a 

 piece of asbestos board, so that about 1.5 inches of the lower part of 

 the crucible shall project below the asbestos board as Lunge a has 

 directed, the asbestos board to be laid flat. Heat with the Bunsen 

 burner for half an hour, allowing the flame to just touch the bottom 

 of the crucible during the first fifteen minutes, and then with the full 

 heat during the last fifteen minutes. (Never let the inner cone of the 

 Bunsen burner strike the crucible.) During the first five minutes of 

 heating with the full flame keep the crucible in an upright position, 

 then remove the cover and tilt the crucible so as to fuse any material 

 which may have crept up the sides. Then return the crucible to the 

 upright position, replace the cover, and heat for five minutes more. 

 When the fusion has solidified, and before it has entirely cooled, place 



a Chemisch-Technische Untersuchungs Methoden, 1904, 1:428. 



[Cir. 56] 



