IRON, MANGANESE' 'AND' cklJjit/M'''''' '-''ioi 



through the filter paper with dilute sulphuric acid. The 

 solution is transferred to a small conical flask fitted with 

 a singly bored stopper and delivery tube bent twice at 

 right angles, the end dipping under distilled water in 

 a beaker. Pure zinc is added to the liquid in quantity 

 sufficient to reduce all the iron present, and the latter 

 is then determined by titration with potassium per- 

 manganate solution. 



A weighed quantity (about 5 grams) of zinc should 

 be used for the reduction, and blank experiments per- 

 formed in order to allow for any iron with which it may 

 be contaminated. 



82. Manganese. 



The filtrate from the iron and aluminium determina- 

 tion (80) is concentrated to about 200 c.c. Strong 

 ammonia is added until the liquid is alkaline, and then 

 bromine water is run in until the colour persists after 

 stirring. The solution is heated to boiling, the beaker 

 being kept covered with a clock-glass ; as the bromine 

 escapes the beaker is allowed to cool somewhat, more 

 ammonia and bromine water added, and the mixture 

 then heated as before. This process is continued until 

 the manganese is completely precipitated, which requires 

 from fifteen to thirty minutes. The precipitate is filtered 

 off while still hot, washed with boiling water, dried, 

 ignited, and weighed as MngO^. 



83. Calcium. 



The filtrate from the manganese is concentrated to 

 100 c.c. or so, if necessary, rendered alkaline with 

 ammonia, and while still boiling treated with saturated 

 ammonium oxalate solution so long as any precipitate 

 is formed. Too great excess of the precipitant is to be 

 avoided. After precipitation the liquid is boiled for ten 



G 2 



