384 On the Method of Assaying Silver. [No. 4, 



The stoppers (previously dipped in distilled water) are then care- 

 fully replaced and the bottles are allowed to stand for five minutes. 

 The bottles are next well shaken two and two by the laboratory 

 workmen for three or four minutes till the chloride aggregates 

 and rapidly falls down, any particles which may remain attached 

 to the neck or upper part of the bottles are washed down by a 

 quick circular motion, and more distilled water being added to 

 within about two inches of the neck, (great caution being observed 

 in removing and returning the stoppers) ; the bottles are then 

 allowed to rest each in its assigned place on the platform for four 

 hours. 



At the expiration of that period, the clear supernatant liquid 

 (blue coloured when copper is present) is removed by a glass 

 syphon, which is lowered to within an inch of the deposited 

 chloride, the greatest care being taken that none of it is drawn up 

 into the syphon. As each platform is made to revolve on its 

 centre, according as each bottle is syphoned, the operator sitting in 

 one place brings the platform round till the next bottle in order 

 gets under the syphon, which is thus in rotation lowered into each. 

 The fluid escapes from the long leg of the syphon through a 

 funnel fitted in the table to a jar placed underneath. 



After the first syphoning, the bottles are immediately filled 

 again with distilled water, and each gets a quiet circular motion 

 for a few moments, and the precipitate is again allowed to settle 

 as evenly as possible, this time it will be sufficient to allow them to 

 rest for two hours, when they are again syphoned as before and the 

 stoppers returned. 



Under ordinary circumstances these two washings are sufficient, 



but if the silver is evidently " coarse," a third or fourth washing is 



similarly given. 

 "When it is considered that the chlorides have been sufficiently 



washed, the bottles are placed for half an hour in a reclining 



position on their platforms, this causes the chloride to fall and 



settle to one spot and renders its removal from the bottles more 



easy. 



Meantime a pneumatic trough has been got ready, capable of 



containing a batch of twenty inverted bottles ; the trough is filled 



