214 CRUDE COMMON SALT. 



bromine=44.5. Difference obtained=23.69. Then 

 44.5 : 80=23.69 : x (=42.5 bromine). 



By the same indirect method, the amount of iodine 

 contained in a mixture of iodide with chloride or bro- 

 mide of sodium may be determined. 



The iodine may also be determined in a mixture of 

 chloride and iodide of potassium or sodium, by adding 

 a solution of sulphate of copper mixed with sulphurous 

 acid, when the iodine is precipitated as white subiodide 

 of copper, which is then washed. 



This method is also applicable for the approximative 

 separation of iodine and bromine. 



In order to detect iodic acid with nitric acid (in 

 nitrate of soda), a little silver is dissolved in it. All 

 the iodine remains as insoluble iodide of silver. 



114. CRUDE COMMON SALT. 



I. A weighed quantity of the moist salt is dried for 

 some time at about 100, then heated to about 300 in 

 a covered crucible, and the water determined from the 

 loss. 



II. For the estimation of the sulphuric acid, the salt is 

 dissolved in water (when any insoluble impurities are 

 left), the solution slightly acidified with hydrochloric 

 acid and precipitated by chloride of barium. 



III. The lirne is determined in a larger quantity of 

 the salt, by precipitating it from its solution by oxalate 

 of ammonia, and filtering off the oxalate of lime when 

 it has subsided. 



IV. The filtrate is concentrated by evaporation and 

 mixed with ammonia and phosphate of soda to preci- 

 pitate the magnesia; after the lapse of twenty-four 

 hours, the precipitate is filtered off and washed with 

 ammonia. 



