APPENDIX 309 



APPENDIX. 



Note on the St as Pipette. 



The Stas pipette used by the writers in the assaying of silver 

 delivers a nearly constant volume of liquid as shown in the following 

 rtatement : — 



Weight of water at 70° F. delivered by the Stas Pipette. 

 Time occupied in delivery = 13 seconds. 



Experiment 1 1000*140 grains 



TT 1000-146 



III 1000-120 



Mean 1000-13X3 „ 



In the arrangement of common forms of the pipette, a shallow 

 bell-shaped glass is suspended over the top of it. Any excess of the 

 liquid, which is introduced from below and is projected upwards, 

 strikes against the glass and is caused to drop down into the glass 

 dish adapted to the neck of the apparatus. There is in this arrange- 

 ment a constant danger of the dish overflowing, and even of the liquid 

 being splashed out on the table. 



The arrangement employed by us consists of an overflow tube 

 instead of the bell-shaped glass, fr is said to have been first devised 

 by the late Mr. W. E. Dubois, assayer in Philadelphia Mint, and has 

 been adopted in that mint and also in the Royal Mint in London. 

 In the form used in those institutions it is constructed of gutta- 

 percha. But as made by us it is of glass, and with a little mani- 

 pulation in the blow-pipe, may he easily constructed in the laboratory 

 from a piece of bulb-tubing. 



