102 



the thermostat. Drops of the aqueous solution of variable size thus remain 

 suspended in the chloroform layer, making it impossible to obtain concord- 

 ant results when different samples are titrated. Fortunately this diffi- 

 culty may be easily overcome by merely rotating the solutions in glass- 

 stoppered bottles in the thermostat. For this purpose the bottles are fast- 

 ented to the axle of the rotary stirrer of the thermostat after the familiar 

 method of making solubility measurements, and allowed to rotate several 

 hours (one to three), when the two phases invariably separate perfectly 

 clear, with a sharply defined bounding surface. In order to establish the 

 equilibrium between the solution of the hydrolysed salt and the chloroform, 

 the latter is vigorously shaken with the aqueous solution in a stoppered sep- 

 aratory funnel. The phases are allowed to separate, after which the water 

 layer is removed as completely as practicable, and another portion of the 

 solution is added. This process is repeated until three portions have been 

 shaken up with the chloroform ; a fourth portion is then rotated with the 

 chloroform, at a constant temperature, as described above. It is important 

 to remove the sample of chloroform for titration without contamination by 

 any of the aqueous sohition. This may be easily done by means of a 

 syphon. The short limb of the glass tube is sealed in the flame, and a 

 small thin bulb blown on the end. It may then be passed, closed, through 

 the aiiueous layer, and opened by breaking against the bottom of the bottle. 

 The chloroform is syphoned into a clean, dry, vessel, measured, and titrated 

 with 0.02 Normal hydrochloric, or nitric, acid, using methyl orange as in- 

 dicator. Enough pure water should be added to make a layer of convenient 

 depth to view the color of the indicator ; since the latter does not enter the 

 chloroform, and the stoppered vessel should be vigorously shaken at in- 

 tervals during the titration. 



The distribution coefficient of ammonia between chloroform and water 

 was measured, at 38°, at concentrations 0.1, 0.05, and 0.02 Normal, and the 

 mean of eight measurements gave 27.36. This is the ratio of the concen- 

 tration of the undissociated ammonia in the aqueous solution to the con- 

 centration of the ammonia in the chloroform. 



The method was applied to the measurement of the degree of hy- 

 drolysis of Na.NIIjl'Oi. at 18°. and concentrations 0.1, 0.05, and 0.02 molal, 

 with the following results : 



