34 IOWA ACADEMY OF SCIENCE 



amount to give an abundant crystallization on cooling to the 

 desired temperature of the experiment. The calibrated pipet 

 was so inserted as to leave its tip above the surface of the solu- 

 tion. The whole was then placed in the bath and when solution 

 and bath were near the same temperature the air was started 

 through the pipet which was then lowered into the solution. At 

 the end of a two-hour period the pipet was raised slightly, its 

 stop-cock was turned and the hose conducting the air was re- 

 moved. In a few moments the solution became perfectly clear, 

 and the pipet was filled with it to the stop-cock by suction. The 

 pipet was removed, washed, dried and weighed. The solution 

 was run into the titration flask, and the pipet was washed into 

 the same with warm water. The whole was then titrated. From 

 the weights and known volume of the pipet, the concentration 

 per gram and per cc. and also the density of the solution could 

 be readily calculated. 



No filtering device for the pipet was necessary, nor any drip 

 cap, since the solution could not run out till the stop-cock was 

 opened. With other substances which settle slowly or not at all 

 it would be necessary to use a filtering device of gauze or other 

 material as in other methods. In such case it would probably 

 be better to pass the air into the solution through an extra tube 

 and not through the pipet. 



After pipetting out at the end of the first experiment the test- 

 tube and remaining solution were left in the bath. After empty- 

 ing the pipet and drying it, it was reinserted and a second ex- 

 periment was carried out extending over an additional period 

 of two hours, or four hours in all. The duplicate experiments 

 give almost perfectly concordant results. These and other data 

 en the acid phthalates are reserved for another communication. 



Chemical Laboratory, 

 Grinnell College. 



