THE ATOMIC WEIGHTS OF 



FIG. 1. 



was effected by a modification of the well-known funnel-top seal 



suggested by T. W. Richards. The device is shown in figure 1. 



The auxiliary glass bulb (a) is easily made from a round-bottomed 



flask of suitable dimensions ; with 

 accurately blown ware an excellent 

 seal may thus be obtained without 

 grinding. The opening at (c) should, 

 of course, be in proper alignment 

 with the constriction at (6), which 

 serves as a seat for the condenser. 

 The neck of the bulb has two side- 

 vents (dd) and is loosely packed with 

 glass wool, held in position by a 

 clamp of platinum wire. Glass wool 

 was used because even in careful 

 boiling a very slight spray of the solu- 

 tion itself may reach this part of the 

 apparatus. 

 The water obtained in the preceding way was used in the 



recrystallizations. In the quantitative determinations small 



quantities of water were to be evaporated 



to dryness, and it was prepared by distil- 

 ling once more from an all-platinum still ; 



it was freshly prepared for each deter- 

 mination and stored in a platinum 



vessel. The "head" of the platinum 



still used is indicated in figure 2. The 



stirrup-shaped "spray-guard" (e) was 



inserted into the ground-in neck of the 



condenser and held in position by the 



pins (/). This still was also used for the 



distillation of hydrofluoric acid. In an 



apparatus of moderate dimensions, and 



particularly when the liquid is to be 



distilled with other dissolved or suspended substances, traces 



of such matter may reach the dome of the condenser, in spite 



of all precautions in heating. It is under such conditions that 



the "spray-guard" just mentioned is of value. 



FIG. 2. 



