478 Mr. W. Crookes on the Atomic Weight of Thallium. [June 20, 



W= weight in air, 

 w— weight in water, 



«=sp. gr. of air as compared with water j 



then 



• i , . W—aw 



x— weight in vacuo= , 



1 — a 



where a=0'001225, and 



1_g=0-998775. 



Results of the Adjustment of Standard Grain- weights (Platinum set). 



Weights. 



True value in 

 air 30 in. 62° F. 



Weight of air 

 displaced. 



volume in 

 water of max. 

 density. 



grs. 



grs. 



grs. 



grs ; 



1 AAA. 

 1UUU 



1 AAA. AAA AAA 



1UUU UUUUuU 



0oo^71 



47'51 



oOO* 



r-AA AAGOvfA 



599-998340 



035533 



28-97 



300* 



OAA AAAO/IA 



300-00024U 



0-01 ^501 



14*27 



200' 



1 AA AAOA1 A 



199 998910 



0011bo4 



9-51 



100- 



99-991420 



0-005887 



4-80 



60- 



59-993232 



0-000483 



2-84 



30- 



29-999991 



0-001668 



1-36 



20- 



19-999984 



0-001104 



0-90 



10- 



9-998477 



0-000490 



0-40 



6- 



5-998268 



0-000355 



0-29 



3- 



3-000469 



0000171 



0-14 



2* 



1-999839 



0000113 



010 



I- 



0-998980 



0-000055 



0-04 



•6 



0-602350 



0-000035 



0-03 



•3 



0-303600 



0-000017 



0-02 



•2 



0-203240 



0-000011 



0-01 



•1 



0-098110 



0-000005 



0-004 



•06 



0-061472 



0-000003 



0-003 



•03 



0-030561 



0-000002 



0-002 



•02 



0-022884 



0000001 



0-001 



•01 



0-014097 



000001 



00004 



*-01' 



0-009997 



o-oooooi 



0-0004 



*-01'' 



0-009967 



000001 



0-0004 



The value of each weight in air, plus the weight of air displaced, is, of 

 course, the weight in vacuo. 



The Glass. 



The flasks and vessels used were of the hardest Bohemian glass, and as 

 thin as they could be employed. When practicable, vessels of old green 

 German glass were used ; neither this nor Bohemian glass is practically 

 affected by reagents. 



No cork or luting was employed in the distillations &c. ; in most cases 

 the apparatus was blown in one piece, and the operations performed in a 

 vacuum. The apparatus, which was weighed, was entirely composed of 

 glass suspended with platinum- wire loops : fingers were never allowed to 

 touch it after the first weighing. 



The weight of tubes, bulbs, and flasks, even of hard Bohemian glass, 

 constantly diminishes when the glass is long heated in a spirit- or gas- 



* Riders. 



