﻿10 Prof. R. Bunsen on the Washing of Precipitates. 



requisite number of decantations to reduce the amount of impu- 

 rity to the ■— 1 — part was 5*2. The times observed were as 



J 5 0000 r 



follows : — 



ii. 



For the first decantation to run through the filter. 15 



„ second „ „ „ 12 



third „ „ „ 18 



„ fourth „ „ „ 15 



fifth „ „ „ 18 



In transferring the precipitate to the filter . . 30 



Time required in washing 108 



Weight of the precipitate . . . 0*2458 grm. 

 Volume of wash-water nY . . . 1050 cub. centims. 



III. 



Experiment repeated, Number of decantations 7. Other cir- 

 cumstances the same as in the foregoing determination. 



Time required in washing . . . 140' 

 Weight of the precipitate . . . 0*2452 grm. 

 Volume of wash-water .... 1200 cub. centims. 



IV. 



After ten decantations. 



Time required in washing . . 180 f 

 Weight of the precipitate . . 0*2443 grm. 

 Volume of wash-water . . . 1750 cub. centims. 



By filtration with the platinum cone and the pump the follow- 

 ing results were obtained : — 



V. 



In transferring the precipitate to the filter (17 cub. cenO ' 



tims. water) J 



For the first addition of water (25 cub. cent.) to run through. 2 



„ second „ „ „ 3 



„ third „ „ „ 2 



„ fourth „ „ „ 2 



>> ^th „ „ „ 2 



In draining the precipitate 2 



Time required 19 



Weight of precipitate .... 0*2435 grm. 

 Volume of wash-water .... 142 cub. centims. 

 Pressure in manometer . . . 0*576 metre. 



