CH. XIII.] ACETONE BODIES. 351 



just boiling whilst A is allowed to boil briskly. The first appear- 

 ance of turbidity in E is noted and the distillation allowed to 

 proceed for another six minutes. Remove plug B and turn out 

 the flames. Detach tube D from the condenser and wash it with 

 a jet of distilled water into E. Allow the fluid to stand for 10 

 minutes. 



2. Filtration of the mercury compound. Use an apparatus 

 similar to that shewn in fig. 33, p. 259. The Gooch crucible should 

 be of 10 cc. and the filtering flask of 250 cc. capacity. First prepare 

 the crucible. Cut a filter paper slightly larger than the bottom of 

 the crucible, place it in position and moisten it. Then pour in a 

 suspension of washed asbestos fibre and form a mat of this by 

 applying suction. A small amount of a suspension of washed 

 powdered pumice should next be filtered to partly close the pores 

 of the filter. 



Filter the fluid in flask E through this. If the first portions of 

 the filtrate are cloudy they must be refiltered. Wash the precipitate 

 with cold water till free from silver. 



3. Solution of the mercury compound. By means of a glass rod 

 with a pointed hook transfer the filter mat to an Erlenmeyer flask. 

 Place the crucible in the neck of the flask and wash it through into 

 the flask with 10 cc. of the acid mixture. The point of the rod should 

 also be washed with a little of this solution. Add i cc. of the 

 potassium permanganate and boil till colourless. Add more of the 

 permanganate, a few drops at a time, till the brown tinge persists in 

 the boiling mixture for about two minutes. Discharge the colour 

 by the addition of a few drops of yellow nitric acid. 



4. Titration of the mercury. Cool thoroughly under the tap 

 and add 2 cc. of the iron alum. Titrate with the diluted thiocyanate 

 against a white ground until a very faint pinkish brown tinge is 

 permanent. The end point is quite sharp, but it must be noted that 

 after it is reached a considerable amount of thiocyanate can be 

 added without appreciably darkening the tint. 



Calculation. From the amount of thiocyanate required the amount of 

 mercury can be found. 



i mg. Hg = 0-0606 mg. acetone. 



