On the Maximum Density of Water. 387 



results are given in a paper on the Solubility of Isomeric 

 Organic Compounds &c, published in 1888 (Chem. Soc. Journ. 

 Trans. 1888, pp. 782-802). Their results are by no means 

 concordant, owing no doubt to the method of conducting 

 the experiments, for which reference must be made to the 

 original paper. The general form of the curves representing 

 their results is the same as that given by my experiments, as 

 will be seen by reference to fig. 4, Plate .VIII., in which I 

 have plotted my results, and side by side with them the 

 curves given by Carnelley [loc. cit.). 



Here the subject must be left for the present. For although 

 there are many points of interest raised, and some general 

 conclusions of importance to be deduced, the discussion of 

 these is best deferred until experiments at present in progress 

 on the molecular volumes of such solutions have been 

 completed. 



XLV. On the Maximum Density of Water. 

 By H. M. Vernon, Scholar of Merton College, Oxford*. 



T 



HOUGH the fact that water has not a regular dilatation,, 

 but reaches a maximum density at about 4° C, has been 

 universally known for a very long time, apparently no expla- 

 nation has yet been offered of this seeming anomaly, which is 

 of such vast importance in nature. The object of this paper 

 is to bring forward a few experiments which afford an inter- 

 pretation of the fact. 



If the fact of the irregular dilatation of water be carefully 

 considered, it will be seen that the only possible explanation 

 of it is that some change in the position of the water molecules 

 towards each other takes place at about 4° C, whereby such 

 a considerable variation in the density is caused. It is, there- 

 fore, probable that at this temperature some thermal change 

 will also take place. If a volume of water be heated and 

 allowed to cool without being subjected to any external varia- 

 tions of temperature, it is evident that if such a thermal 

 change does occur at 4° C, the rate of cooling of the water 

 will not be regular at this point. To test this, experiments 

 were made on the rate of cooling of water from about 30° C. 

 to slightly below 0° C. 



A volume of distilled water, varying in different experi- 

 ments from 30 cub. centim. to 60 cub. centim., was placed in 

 a glass flask which was suspended inside a large beaker sur- 

 rounded by a freezing-mixture of ice and salt. The vessel 



* Communicated bv the Author. 



2 F2* 



