Qualitative Analysis 139 



Method of Analysis. 



Dissolve the group precipitate of sulphides and hydroxides (adding 

 the filter if difficult to separate from the precipitate) in warm 6N HCl, 

 adding a few drops of HNO3 if necessary (if cobalt or nickel is present). 

 If the filter was added, remove the fibers by sucking the solution through 

 a Hirsch funnel. Wet the pulp remaining in the funnel with ' water 

 and draw the water into the filtrate. Except for particles of sulphur 

 the pulp will be white after this treatment. 



Boil the filtrate for a minute and then add 30 per cent NaOH 

 solution until a precipitate forms and persists after shaking or, if no 

 precipitate appears, until solution is strongly alkaline. If there is a 

 precipitate, add a further excess of 5-lOcc. NaOH. Cool and add l-3g. 

 NaoOi; a little at a time with stirring. Add about half a gram of solid 

 Na2C03 and boil for a minute or two. Dilute with two volumes of hot 

 water and boil for three minutes. Filter hot through an ordinary filter, 

 the writer using a suction filtration by preference. Wash the precipitate 

 on the filter with hot water, collecting the w^ashings with the filtrate. 

 The filtrate is treated as directed in Noyes' "Qualitative Analysis" for 

 the separation of the first division metals. 



The paper carrying the precipitate is spread out in a dish and 

 covered with 15cc. boiling 6N HNOa. This treatment dissolves or loosens 

 the precipitate from the paper so that it can be transferred to a beaker. 

 The paper is washed with another portion of hot acid and the solution 

 added to the other. The solution is evaporated to lOcc. and lOcc. 16N 

 HNO.i added. The boiling solution or suspension, as the case may be, is re- 

 moved from the flame and about a gram of KClOt is added with stirring. 

 This produces complete precipitation of the manganese as the oxide unless 

 there is a very large quantity of it present. Twenty cc. hot water is 

 added, the solution or suspension boiled and filtered hot through an 

 ordinary filter. Oxalates, if present, slov/ up the precipitation of the 

 manganese and sometimes necessitate a second evaporation and addition 

 of chlorate. 



The filtrate contains iron, cobalt, and nickel, and fourth group 

 ions if phosphates, oxalates, etc. are present. When these interfering- 

 ions are absent, add quickly with stirring a volume of 15N NH4OH 

 5cc. in excess of the volume of HNO3 present. If iron is present it 

 will appear as the brown hydroxide. Quickly heat almost to boiling 

 and filter hot. Wash the precipitate on the filter with 2-.5cc. NH^OH, 

 collecting it with the original filtrate. Confirm iron in the precipitate. 



In a tall 150cc. beaker boil off the ammonia from the filtrate until 

 its odor is weak but noticeable. Pour off about one-fifth of the solution 

 and test for nickel by adding a few drops of dimethylglyoxime solution. 

 If nickel is present, a red precipitate will form at once. It is never 

 necessaiy to correct for hydrogen ion concentration in this test if the 

 above directions are closely followed. 



Evaporate the remainder of the solution to a syrupy consistency 

 and pour it into a test tube. Cool, and add enough water to bring 

 most of the solid into solution. The reaction at this point is acidic. 

 Add 3cc. 10 per cent KCNS solution and then 2.5cc. amyl alcohol-ether 



