266 TITRIMETRIC METHODS 



sufficient to compensate for it by multiplying the result by the 

 factor, 1.04. 



From the results of various tests, it was shown that the ashing 

 reagent removes all sulfate and phosphate; the presence of calcium, 

 magnesium, and iron in the sample does not disturb the determina- 

 tion. 



Linflerstr0ni-Lang Method for Sodiiiin and Potassium 

 SPECIAL APPARATUS 



Quartz Tubes. These are of clear quartz having an inner diameter 

 of 3.8 mm., an outer diameter of 6 mm., and a length of 20 mm. 

 The cleaning of the tubes requires a special procedure in this case: 

 Completely fill with dil. (1 iV) hydrochloric acid (to dissolve 

 barium carbonate). Wash out and fill with 2 N ammonia (to 

 dissolve silver chloride). Wash out, fill, and heat with cone, 

 sulfuric acid (to dissolve barium sulfate), and finally wash several 

 times with boiling water. In all operations, avoid touching the 

 rim of the tubes with the fingers. 



Incineration Oven. The oven, shown in Figure 65, is made of a 

 solid copper block containing holes 18 mm. deep and about 7 mm. 

 in diameter. Two electric heaters placed at the sides of the block 

 enable a temperature of 440-460° to be maintained. A rheostat 

 is used to obtain lower temperatures and to regulate the heating. 

 The sides and bottom of the oven are insulated with asbestos. 



Hand Pipette for Ashing Reagent (about 10 fil. capacity). Made 

 of a piece of capillary tubing with a rather wide aperture to avoid 

 plugging b}^ barium carbonate, which forms during pipetting. 



SPECIAL REAGENTS 



Ashing B.eagent. Prepare a soln. containing 1.2% barium chloride 



(BaClo.2H20) and 3.2% barium hydroxide (Ba(OH)o.8H20). 

 Precipitation Reagent. Dissolve 5.7 g. ammonium carbonate in 



100 ml. 1.5 N ammonium hydroxide. 

 Titration Medium. Prepare a soln. containing 1.20% sodium 



nitrate and 0.40% secondary sodium phosphate (Na2HP04.2H20) 



in 0.10 N nitric acid. 

 Silver Nitrate Solution (0.02 N). Dissolve 0.3398 g. silver nitrate 



in 100 ml. titration medium. 



