80 Dr. Meyer Wilderman on the Velocity of 



liquid would ultimately assume at the given temperature of 

 the surrounding medium, when no ice is present and the 

 liquid is stirred), C is the velocity constant of cooling by the 

 surrounding medium, C is the velocity constant of crystalli- 

 zation or of the melting of the ice." It was further shown 

 how to arrange the conditions of the experiment so that 

 the observed apparent point of equilibrium T ; may differ 

 from the real point of equilibrium T only by 0°*00002 or 

 0°' 00004. It was shown that even in one of the most deve- 

 loped methods the error arising from the arrangement of the 

 equilibrium was already 160 to 200 times greater than in the 

 method given, that is, it amounted to several thousandths of 

 a degree. To get a correct point of equilibrium the values 

 of T^— T, C, T — T ov , K, CK must be properly investigated, and 

 every one of them correspondingly arranged by the conditions 

 of the experiment. In a paper " On Real and Apparent 

 Equilibrium/'' which will be shortly published, the investi- 

 gation is extended to boiling-points, solubilities, vapour- 

 pressures, sublimation, &c. — in a word, to all kinds of 

 " perfect " equilibrium. As this part of the research consists 

 in the consideration of a very great number of details, the 

 reader is referred to the above-mentioned publications, and 

 the results only are here given. 



Four and a half litres of liquid were always used for an 

 experiment. The velocity of cooling of the liquid, beaker, 

 and stirrer in the air-bath, when the stirring and other con- 

 ditions were the same as in an experiment on velocity of 

 reaction, was first measured and the values of C in Newton's 



equation for cooling -j— =C(T^ — T), and T g were determined. 



The value of C was found to be o, 004 per minute for pure 

 water. The temperature of the air-bath was kept constant 

 during the time of the experiment, within 0°'l or even 0°*05. 

 The rate of stirring was 36 per minute, and was done by an 

 electromotor or by hand. Experiments were then carried 

 out for different temperatures of the air-bath and for different 

 temperatures of the room. The values of T^ for different 

 conditions of the air-bath and room were thus obtained. 

 For further particulars concerning the determination of C 

 and T^ see the above-mentioned publications in Phil. Mag. 

 Dec. 1897, and in the Zeitschrift fur physikalische Chemie. 

 From the photographed curves of the different reactions 

 which form the subject of this paper, the values of C, C and 

 of T -- T op , K are known in each individual case. Having 

 thus C', T-To,,, K, C, T 9 -T' or T,-T , the difference 

 between the apparent and the real point of equilibrium can 



