SCIILUNDT SPEED OF THE LIBERATION OF IODINE 6 



was prepared by dissolving 165.54 g. of the pulverized 

 salt, dried at 100" C, and making it up to one liter. The 

 normal hydrochloric acid was standardized on calcite. The 

 potassium chlorate was tested for sulphates, nitrates, 

 chlorides, the heavy metals, and the alkaline earths, and 

 found to be j3ure. The solution of this salt was three times 

 normal and was prepared by taking 61.25 g. of the dry crys- 

 tallized salt to a liter. A twentieth normal solution of so- 

 dium thiosulphate served for titration. It was prepared by 

 dissolving 12.4 g. of the pure crystallized salt per liter of 

 water. The strength of this solution was verified by test- 

 ing with deci-normal iodine solution. The starch paste 

 used was quite dilute and was prepared by stirring 

 up two to three grams of the fine starch with cold 

 water. Three to four hundred cubic centimeters of 

 boiling hot water were then added and the mixture well 

 stirred. This paste was then filtered, and the filtrate used 

 as indicator. A fresh solution was frequently prepared. 



Conduct of Experiments. — The entire series of investiga- 

 tions was conducted at 100° C. The mixtures were pre- 

 pared by measuring out the desired equivalents of the dif- 

 ferent components, cooling them to 0°C. in ice water, and 

 then mixing them. Samples of 20 cc. of the mixture were 

 then quickly taken out and put into ordinary six- inch 

 test tubes. The tubes were quickly sealed, but all the 

 time kept as cool as possible. The samples were then 

 plunged into a large kettle of boiling water and kept at 

 this temperature. At definite intervals samples were 

 taken out and plunged into ice water, thus quickly check- 

 ing the reaction. After one minute the test tubes were 

 broken, washed with cold water, and the iodine determined 

 by means of a twentieth normal solution of sodium thio- 

 sulphate. 



The test tubes were sealed at about the same distance 

 from the end, thus keeping the pressure nearly constant. 

 Whenever it was found expedient to work with samples. 



