Reaction before Complete Equilibrium. 85 



time to the temperature of the air. Holding the cube with a 

 thick perfectly smooth sheet of indiarubber, it was polished on 

 a heated thick smooth iron plate, and measured by a wooden 

 cm. ruler until the correct shape was obtained. The ' cube 

 was then quickly weighed on a sufficiently sensitive balance 

 (placed on very smooth and thick sheets of indiarubber) 

 and rapidly brought into the cage for the experiment. From 

 its weight we know very accurately its surface at the beginning 

 of the reaction, and from the quantity of the liquid, the weight 

 of the beaker and stirrer and their initial temperature T ov , and 

 their temperature t at the time t, the surface of the ice cube 

 at the time t can be calculated. At the end of the reaction 

 the ice was again weighed. It was found that a considerable 

 part can be melted before the ice loses its cubic shape. 

 Experiments were at first made, without success, with a view 

 of obtaining the ice in the form of a sphere, either by com- 

 pressing pure ice, or by freezing water in two Magdeburg- 

 hemispheres or in glass balls, allowing the water from the 

 inside to escape through a tube, or by turning the ice on a 

 In the, &c. The number of stirrings was about (>() per minute. 



IV. The Results obtained. 



By the method given above the velocity of ice separation, 

 ice melting, and of the separation of salts from supersaturated 

 solutions were investigated, and the equations concerning the 

 total length of the curves were found. All these reactions 

 prove to be regulated by one and the same general law. which 

 is given in the following differential equation : 



f T =K%-t){t-t m +K) (1) 



Since all reactions were investigated within limits of less 

 than one degree, we can very well assume that the velocity 

 constant K' remained during the reaction the same. 



In Plate II. two photographic curves (reduced to half 

 their size) are given — one representing the velocity of sepa- 

 ration of ice from an NO ; .K solution, the other the velocity 

 of separation of solid N0 3 K from a supersaturated N0 3 K 

 solution. The velocity of reaction is very different in the 

 two eases, being very much slower in the case of the separation 

 of salt. The nature of the curve, however, is in both cases 

 the same, as is to be seen from II'., which represents II. when 

 instead of the actual 1 cm. = l second, 1 cm. = 10 seconds is 

 taken. The same result was found in the case of about sixty 

 other curves, to be published later. The results obtained 

 from these curves are oiven in the followino: Tables I. and II 



