BAKIX<; I>0\VI>KK AND IJAKINC < ' 1 1 KM ICAI ,S. 



173 



gram. M should be refilled when its weight has increased 0.75 gram and N 

 after an increase of 0.1 gram in weight. 



Use best rubber for all connections, applying a trace of castor oil as lubri- 

 cator. For connections of the weighed tubes use rubber tubing boiled in weak 

 lye, washed and dried. Apply also a little castor oil, which is thoroughly wiped 

 off again before connecting the tubing. 



Before using the apparatus fill H and K with carbon dioxid in order to 

 saturate the alkalinity of the calcium chlorid, and exhaust after several hours. 



(3) DETERMINATION. 



Weigh the tubes M and N, taking precaution that they are of the same tem- 

 perature as the air in the balance room. Shortly before weighing open the 

 mhos for a moment to allow equalization of air. Note thermometer and barom- 

 eter. Connect tubes with the apparatus and make sure that all joints are 

 tight by closing A at the bottom, opening all cocks, starting the aspirator, and 

 observing P, in which the liquid must soon come to a standstill. Then discon- 

 Inect the aspirator, close B, remove F, put in the substance (use about 1 gram 

 of sodium carbonate or calcium carbonate, or about 2 grams of baking powder), 

 connect F, and start the cooler. Introduce acid and water through D, lifting E 

 slightly, and allowing only small quantities of the acid and water to enter at 

 the time. Use only carbon dioxid free water. Light the burner, heat to boiling, 

 and reduce the flame to keep the liquid just at the boiling point. If no more air 

 passes P, start the aspiration. When water stops running, opert B carefully 

 and adjust the outflow of the aspirator by raising or lowering the syphon to 

 (half the safe speed. 



(In order to find the allowable rapidity of the air current, proceed as follows: 

 jCharge the apparatus exactly as for an analysis, leaving out the carbonate. 

 |Begin to aspirate at the rate of about 50 cc per minute. After 2 liters have been 

 ispirated weigh the tubes. If they have lost in weight, repeat the experiment 

 rith 40 cc per minute, and so on until the weight of the tubes remains constant. 

 [f the work has been done with due precaution, the first tube must have lost 

 just as much as the second has gained. Do not exceed the safe speed thus 

 mnd. ) 



After M has become cool increase the current to full safe speed and aspirate 

 iltogether 3 liters, continuing boiling to the end of aspiration. After the tubes 

 lave assumed the temperature of the balance room open for a moment, weigh, 

 iote again thermometer and barometer, and apply correction according to the 

 following formula?: 



(A 2 A 1 ) XT and +(B 2 B 1 ) XB 

 [n which 



A 1 is the temperature at first weighing in C, 

 A 2 is the temperature at second weighing in C, 

 B 1 is the air pressure at first weighing in mm, 

 B 3 is the air pressure at second weighing in mm, 

 T and B are constants found as follows : 



G= weight of empty tubes. 

 F=weight of fillings. 

 The specific gravity of glass=2.7. 

 The specific gravity of filling=2.0. 

 The specific gravity of brass=8.5. 



Change of weight of 1 cc air with 1 =0.0000039 gram. 



Change of weight of 1 cc air with 1 mm pressure=0.0000015 gram. 



