192 THE EAKL OF BERKELEY, MR. E. G. J. HARTLEY AND DR. C. V. BURTON: 



TABLE IIlA. Mean Values. 



water) of the solution ; (3) the water content of the hydrated salt used in the " make 

 up " of the solution ; (4) the name of the tube used ; (5) the apparent turning-point, 

 i.e., the pressure at which no movement of the water gauge takes place; (6) the 

 movement of the water level, in millimetres, in 15 minutes, caused by the "guard-ring 

 leak" ; (7) the time the pressure was on the solution ; (8) the solution leak, i.e., the 

 total amount of Ca a Fe(CN) come through the membrane during the time in 

 Column (7) ; (9) the movement of the water level, in millimetres, in 15 minutes, 

 caused by an increment of pressure of "3 4 atmosphere ; (10) the apparent turning- 

 point [Column (5)], corrected for "guard-ring leak"; as there is practically no 

 correction for "solution leak," the numbers in column (10) can be taken as the osmotic 

 equilibrium pressure of the solution when there is a pressure of 1 atmosphere on the 

 solvent. 



COMPRESSIBILITY OF THE SOLUTIONS. 



An attempt was made, in view of other work with more compressible solutions, to 

 design the apparatus so that accurate results might be obtained. The piezometer is 

 represented by fig. 5. The gunmetal vessel A is filled with water and connected by 

 B and C to a Schaffer and Budenberg dead-weight pressure apparatus. 



The " llobax " * Jena glass tube D, 19 mm. external and 12 mm. internal diameter, 

 is made pressure-tight with the gunmetal piece E by means of a dermatine ring F, 

 which is compressed between a shoulder and a metal sleeve actuated by a nut, J. 

 The lower end of the tube is closed pressure-tight in a similar manner and the tube is 

 prevented from slipping out by four distance stays such as G G. The compressibility 

 vessel H, which is filled with the solution to be examined, is of No. 16 m Jena glass. 

 This glass was selected as its compressibility has been carefully determined by SCHOTT 

 and STRAUBEL.f The bulb is of about 15 c.cm. capacity and the stem, open at the 

 lower end, is graduated into millimetres (1 mm. of the bore has a -capacity of 

 0'0002 c.cm.). The whole tube, bulb, and stem were carefully calibrated in the usual 



* The Robax tubes were found to withstand pressure fairly well, but after considerable use they burst 

 at a lower pressure than that originally reached ; hence, after using a tube for four or five observations at 

 100 atmospheres, it must be replaced by a new one. 



t SCHOTT and STRAUBEL see references in LANDOLT and BORNSTEIN'S tables, 3rd ed. 



