8 



OSMOTIC PRESSURE OF AQUEOUS SOLUTIONS. 



THE FORMATION OF THE CYLINDERS. 



A section of one of the steel presses in which 

 the clay is formed into cylinders is shown in 

 Figure 1 A. The barrel (1) is slightly tapered 

 internally, the diameter at the bottom being 

 0.005 inch greater than at the top, in order to 

 insure the ready release of the clay cylinder 

 when it is to be pushed out of the lower end 

 of the press. It is threaded at both ends to 

 receive the caps (2 and 3). The cap at the 

 lower end (2) is bored to permit the escape 

 of the water which is squeezed out of the clay. 

 The cap at the upper end (3) is bored and 

 threaded internally to receive the hollow plug 

 (4). The steel disks (5 and 6) are also bored 

 to facilitate the escape of water. The disks 

 (7 and 8) are of porous hard-burned clay or of 

 asbestus. 



The upper steel disk (6) is less simple than 

 it appears in the figure. In reality it consists 

 of two grooved disks separated by hardened 

 steel balls (bicycle balls), as shown in Figure 

 1 B. The upper half turns readily with the 

 plug (4), while the lower half remains sta- 

 tionary, thus preventing any twisting of the 

 clay beneath. If a single disk is used, the 

 clay is twisted in a direction the reverse of that of the screw, and 



collects in the outer vessel. As the level of the contents of the pot 

 recedes, more clay is added until no more can be introduced. 

 In the meantime, the level of the water in 

 the outer receptacle is kept, by means of an 

 automatic siphon, just high enough to permit 

 the complete submersion of the cathode. 

 When the clay becomes so far dried that the 

 mass begins to crack at the top, it is packed 

 down with a heavy pestle. In this way the 

 excess of water can be separated from the 

 clay much more rapidly and even more com- 

 pletely than by nitration under diminished 

 pressure. The method can also be applied 

 with advantage to the separation of water 

 from, and even to the washing of, other solids 

 which, like clay, are filtered with difficulty. 

 The voltage employed is 110 or 120. 



B 



Fig. 1. 



^4. Steel press for clays. (1) Bar- 

 rel", (2) lower cap; (3) upper cap; 

 (4) plunger ; (5) and (6)steel disk ; 

 (7) and (8) porous clay disk. 



B. Ball-bearing disk, used in 

 place of (6) to prevent twisting 

 of clay. 



